B THNG TIN V TRUYN THNGCC VIN THNG----------------------------------------

BO CO KT QU NGHIN CU TI

XY DNG QUY CHUN K THUT QUC GIA V PHI NHIM TRNG IN T I VI CC I PHT THANH V TRUYN HNH

M S: 25-11-KHKT-TC

Ch tr: Nguyn Xun Hi Cc Vin thngNhng ngi tham gia:TS. Nguyn Phi TuynThS. Nguyn Vn KhoaKS. Nguyn c NamTS. Nguyn Hoi Anh

H Ni - thng 12 nm 2011

6

MC LC

M U7CHNG 1. NGHIN CU CC QUY NH V KIM NH I V TUYN IN91.1.Lut Tn s v tuyn in91.2.Lut Vin thng101.3.Ngh nh 25/2011/N-CP ngy 06/4/2011101.4.Thng t s 16,17/2011/TT-BTTTT11CHNG 2. KHO ST TNH HNH THC T TRONG NC V CC I PHT THANH, TRUYN HNH142.1.Mc tiu pht trin pht thanh truyn hnh n nm 2020142.2.Cng ngh v cc loi pht thanh, truyn hnh ti Vit Nam142.2.1.Cc cng ngh pht thanh, truyn hnh ti Vit Nam142.2.2.Quy hoch bng tn cho h thng pht thanh truyn hnh ti Vit Nam152.2.3.Cc cp i pht thanh ti Vit Nam152.2.4.Cc cp i pht hnh ti Vit Nam :162.3.Kho st thc t v cc i pht thanh, truyn hnh trong nc162.3.1.i pht thanh AM - Bng MF (526,25 - 1606,5 KHz)162.3.2.i pht thanh AM - bng HF (3 - 30MHz)172.3.3.i pht thanh FM - Bng I VHF (54 - 68 MHz)172.3.4.i pht thanh FM - Bng II VHF (87 - 108 MHz)172.3.5.i truyn hnh - Bng III VHF (174 - 230 MHz)182.3.6.i truyn hnh - Bng UHF (470 - 806 MHz)182.3.7.i truyn hnh k thut s pht trn knh 6 n knh 5919CHNG 3. NGHIN CU CNG TC TIU CHUN HO CA CC NC V CC T CHC QUC T203.1.Tng quan v nh hng ca sng v tuyn203.1.1.Bn cht ca bc x RF203.1.2.nh hng n sc khe203.1.3.C s xy dng mc phi nhim ln nht i vi bc x RF233.2.IEEE (M)283.3.Lin minh Vin thng quc t (ITU)333.4.Chu u343.5.Canada363.6.c423.7.Vit Nam433.7.1.Gii thiu tm tt v TCVN 3718-1: 2005433.7.2.Gii thiu v TCVN 3718-2: 2007503.8.Nhn xt50CHNG 4. NGHIN CU PHNG PHP O KIM, NH GI PHI NHIM TRNG IN T I VI CC I PHT THANH V TRUYN HNH CA MT S NC TRN TH GII514.1.Canada514.1.1.GL-01 (11/2005) - hng dn o kim cc trng tn s v tuyn in di tn t 3 kHz n 300 GHz514.1.2.TN-329 (2/2011) - Th tc o kim an ton theo Lut an ton s 6 (Mi trng khng c kim sot)564.1.3.TN-261 (2/2011) - Th tc nh gi s ph hp Lut an ton s 6 i vi phi nhim tn s v tuyn in (gii hn phi nhim mi trng khng c kim sot)574.2.M624.2.1.Khuyn ngh IEEE Std C95.3-2002624.2.2.Khuyn ngh IEEE Std C95.4-2002:634.2.3.OET Bulletin 65654.3.Nhn xt65CHNG 5. XY DNG QUY CHUN K THUT QUC GIA V PHI NHIM TRNG IN T I VI CC I PHT THANH V TRUYN HNH P DNG TI VIT NAM675.1.Tn gi v k hiu ca Quy chun675.2.t vn 675.3.S c xy dng cc yu cu k thut675.4.Gii thch ni dung Quy chun695.5.Bng i chiu ni dung QCVN vi cc ti liu tham kho76CHNG 6. KT LUN, KIN NGH776.1.Kt lun776.2.Kin ngh77K HIU VIT TT78TI LIU THAM KHO79PH LC: S LIU KHO ST V CC I PHT THANH, TRUYN HNH80

MC LC CC HNH V

Hnh 1. Ph sng in t20Hnh 2. Hp th bc x RF ca c th theo tn s21Hnh 3. Mt dng nng lng m gii hn SAR trn ton b c th ngi n 0,4W/kg.25Hnh 4. Biu biu din gi tr MPE trong mi trng c kim sot30Hnh 5. Biu biu din gi tr MPE trong mi trng khng kim sot32Hnh 6. Biu mc gii hn phi nhim trng in40Hnh 7. Biu mc gii hn phi nhim trng t40Hnh 8. Biu gii hn dng in cm ng v dng in tip xc trong mi trng c kim sot41Hnh 9. Biu gii hn dng in cm ng v dng in tip xc trong mi trng khng c kim sot41Hnh 10. ng bin trng gn - trng xa ca anten59Hnh 11. Vng hn ch thm nhp ca anten60Hnh 12. Vng khng c min o tng hp60Hnh 13. Trng hp phi o kim nh gi chi tit61Hnh 14. Cc vng trng ca anten61Hnh 15. V tr o ti tng im o71Hnh 16. Hnh v xc nh chiu cao vng tun th ca anten.73Hnh 17. Biu bc x xc nh gc m ca bp sng73Hnh 18. Xc nh vng kho st75

MC LC CC BNG

Bng 1. Danh mc thit b vin thng v i VT bt buc kim nh11Bng 2. Tng hp v cng sut v cao anten ca cc i pht thanh AM16Bng 3. Tng hp v cng sut v cao anten ca cc i pht thanh FM17Bng 4. Tng hp v cng sut v cao anten ca cc i TH VHF18Bng 5. Tng hp v cng sut v cao anten ca cc i TH UHF18Bng 6. Tng hp v cng sut v cao anten ca cc i TH KTS19Bng 7. Bng quy nh gii hn MPE ca tiu chun C95.1-2005 i vi mi trng c kim sot30Bng 8. Bng quy nh gii hn MPE ca tiu chun C95.1-2005 i vi mi trng khng c kim sot31Bng 9.Cng thc tnh ton khong cch tun th ti thiu t anten ca i pht p dng i vi khu vc cng cng33Bng 10.Cng thc tnh ton khong cch tun th ti thiu t anten ca i pht p dng i vi khu vc phi nhim do ngh nghip34Bng 11. Bng quy nh gii hn trng in, trng t v trng in t ca khuyn ngh s 1999/519/EC i vi khu vc cng cng35Bng 12. Bng quy nh mc tham chiu i vi trng in, trng t v trng in t ca khuyn ngh s 1999/519/EC35Bng 13. Mc gii hn dng in tip xc ca khuyn ngh s 1999/519/EC36Bng 14. Bng gii hn mc SAR trung bnh trn c th ngi ca SC637Bng 15. Bng gii hn dng in tip xc v dng in cm ng i vi mi trng c kim sot ca SC637Bng 16. Bng gii hn dng in tip xc v dng in cm ng i vi mi trng khng c kim sot ca SC638Bng 17. Bng gii hn v dng in tip xc v dng in cm ng trung bnh theo thi gian i vi thi gian o nhim khc nhau ca SC638Bng 18. Cc gii hn phi nhim i vi mi trng c kim sot39Bng 19. Cc gii hn phi nhim i vi mi trng khng kim sot39Bng 20. Mc phi nhim RF do ngh nghip v gii hn dng in RF44Bng 21. Mc phi nhim khng do ngh nghip dn xut theo trng in v trng t bin i theo thi gian (gi tr hiu dng khng b thay i)46Bng 22. Bng quy nh khong cch an ton i vi i AM theo GL-0153Bng 23. Bng khuyn ngh khong cch ti thiu t anten pht thanh qung b AM theo C95.4-200264Bng 24. Bng khuyn ngh khong cch ti thiu t anten pht thanh qung b FM, truyn hnh qung b VHF theo C95.4-200264Bng 25. Bng khuyn ngh khong cch ti thiu t anten truyn hnh qung b UHF theo C95.4-200265Bng 26. Bng quy nh mc gii hn phi nhim khng do ngh nghip theo TCVN 3718-1:200568Bng 27. Khuyn ngh mc gii hn phi nhim i vi i PTTH ca VN69Bng 28. Bng i chiu ni dung d tho quy chun v ti liu tham kho76

M U

Ngy nay cng ngh thng tin v tuyn pht trin rt mnh m, ng gp mt vai tr v cng quan trng trong hu ht cc lnh vc ca cuc sng, mang li nhiu tin ch v gp phn thc y s pht trin ca x hi. Trong nhng nm va qua, vic p dng cng ngh thng tin v tuyn vo trong cc lnh vc ca i sng x hi Vit Nam cng pht trin rt nhanh, snh ngang vi cc nc trn th gii.Vn sc khe con ngi lun c quan tm, c bit l x hi cng pht trin, hiu bit ca con ngi v khoa hc k thut cng cao cng nh i sng vt cht tinh thn cng cao th cng quan tm n sc kho ca mnh. Theo nghin cu thc t th sng v tuyn in c th nh hng n sc kho ca con ngi, do m bo khng nh hng n sc kho con ngi th cc thit b pht sng v tuyn in phi m bo tun th cc quy nh nghim ngt v an ton bc x v tuyn in. V mt bi dng v ch ph cp i vi ngi lm vic trong mi trng nguy him, ngy 23/3/2010, B Thng tin v Truyn thng ban hnh Thng t 08/2010/TT-BTTTT hng dn thc hin ch ph cp c hi, nguy him v bi dng bng hin vt i vi cng chc, vin chc, ngi lao ng lm vic trong lnh vc pht thanh, truyn hnh i vi mt s cng vic nh vn hnh, iu khin, sa cha my pht hnh, my pht thanh, my pht sng viba, vn hnh trm truyn dn tn hiu v tinh; lp t, sa cha ng dy phi- anten, mng no ct anten cc i pht sng, pht thanh, truyn hnh,V mt qun l k thut m bo cc i pht sng v tuyn in khng nh hng n sc kho ngi dn, Lut Tn s v tuyn in ngy 23 thng 11 nm 2009 quy nh: Cc i v tuyn in thuc danh mc i v tuyn in bt buc phi kim nh th phi thc hin kim nh. Hin nay Vit Nam cc trm gc in thoi di ng mt t cng cng l cc i pht sng v tuyn in c thc hin vic kim nh t nm 2007 v cng tc kim nh trm gc vn ang c tip tc duy tr.i vi cc i pht sng v tuyn in l cc i pht thanh, truyn hnh, qua kho st thc t cho thy, cc n v hnh chnh cp huyn c i truyn hnh, cc x c cc i pht thanh v hu ht cc i pht thanh, truyn hnh u t khu vc dn c sinh sng v a s cc i ny c cng sut pht sng cao. Tuy nhin vic kim nh i vi cc i pht thanh, truyn hnh cha c thc hin, v vy m bo cc i pht thanh, truyn hnh tun th cc quy nh v an ton bc x v tuyn in th cng tc kim nh cc i pht thanh truyn hnh cn phi trin khai trong thi gian ti. c th trin khai cng tc kim nh i vi i pht thanh truyn hnh th trc tin cn phi xy dng quy chun k thut quc gia v phi nhim trng in t i vi i pht thanh, truyn hnh v phng php o kim, nh gi. Chnh v vy, B Thng tin v Truyn thng giao Cc Qun l cht lng Cng ngh thng tin v truyn thng (nay l Cc Vin thng) thc hin ti: Xy dng quy chun k thut quc gia v phi nhim trng in t i vi cc i pht thanh v truyn hnh, M s: 25-11-KHKT-TC.Trn c s cng c giao, nhm ch tr ti tp trung nghin cu cc ni dung sau:Chng 1. Nghin cu cc quy nh v kim nh i v tuyn in.Chng 2. Kho st tnh hnh thc t trong nc v cc i pht thanh, truyn hnh.Chng 3. Nghin cu cng tc tiu chun ho ca cc nc v cc t chc quc t.Chng 4. Nghin cu vic p dng tiu chun v phng php o kim, nh gi phi nhim trng in t i vi cc i pht thanh v truyn hnh ca mt s nc trn th gii.Chng 5. Nghin cu xut xy dng quy chun k thut quc gia v phi nhim trng in t i vi cc i pht thanh v truyn hnh p dng ti Vit Nam.Chng 6. Kt lun, kin ngh.Trong qu trnh thc hin ti, mc d nhm ch tr ti ht sc c gng nghin cu, tuy nhin cng khng th trnh khi cc sai st, nhm ch tr ti rt mong nhn c kin gp ca cc chuyn gia cng nh cc nh qun l v bn c.Trn trng cm n.NHM CH TR TI

CHNG 1. NGHIN CU CC QUY NH V KIM NH I V TUYN IN

1.1. Lut Tn s v tuyn inLut Tn s v tuyn in s 42/2009/QH12 c Quc hi nc Cng ho x hi ch ngha Vit Nam kho XII, k hp th 6 thng qua ngy 23 thng 11 nm 2009 v chnh thc c hiu lc thi hnh k t ngy 01 thng 7 nm 2010.Mt s khi nim lin quan n i v tuyn in c quy nh ti iu 3 Lut Tn s v tuyn in nh sau: i v tuyn in l mt hoc t hp thit b v tuyn in, bao gm c thit b ph tr km theo c trin khai thc hin nghip v v tuyn in. i v tuyn in c phn loi theo nghip v m i v tuyn in hot ng thng xuyn hoc tm thi. Bc x v tuyn in l nng lng sinh ra dng sng v tuyn in t mt ngun bt k. Pht x v tuyn in l bc x ca mt i pht v tuyn in. Thit b v tuyn in l thit b thu, pht hoc thu - pht cc k hiu, tn hiu, s liu, ch vit, hnh nh, m thanh hoc dng thng tin khc bng sng v tuyn in.Trch nhim qun l nh nc ca B Thng tin v Truyn thng quy nh ti khon 1 iu 5 nh sau: Ban hnh hoc trnh c quan nh nc c thm quyn ban hnh v t chc thc hin vn bn quy phm php lut v tn s v tuyn in; ban hnh quy chun k thut quc gia v thit b v tuyn in, pht x v tuyn in, tng thch in t, an ton bc x v tuyn in.Ni dung qun l an ton bc x v tuyn in c quy nh ti iu 14 nh sau: iu 14. Qun l an ton bc x v tuyn in 1. Bo m an ton bc x v tuyn in l cc bin php nhm ngn nga, chng li hoc gim thiu tc hi ca bc x v tuyn in ca i v tuyn in, thit b v tuyn in, thit b ng dng sng v tuyn in i vi con ngi, mi trng.2. T chc, c nhn s dng i v tuyn in, thit b v tuyn in, thit b ng dng sng v tuyn in phi tun th cc quy nh ca php lut v bo m an ton bc x v tuyn in.3. T chc, c nhn sn xut, nhp khu thit b v tuyn in, thit b ng dng sng v tuyn in thuc Danh mc thit b v tuyn in, thit b ng dng sng v tuyn in c kh nng gy mt an ton bc x v tuyn in trc khi a vo lu thng trn th trng hoc s dng phi thc hin vic chng nhn hp quy, cng b hp quy v s dng du hp quy. 4. T chc, c nhn trc khi a i v tuyn in thuc Danh mc i v tuyn in bt buc kim nh v an ton bc x v tuyn in vo s dng phi thc hin vic kim nh. 5. B trng B Thng tin v Truyn thng ban hnh Danh mc thit b v tuyn in, thit b ng dng sng v tuyn in c kh nng gy mt an ton bc x v tuyn in phi chng nhn hp quy, cng b hp quy v s dng du hp quy; Danh mc i v tuyn in bt buc kim nh v an ton bc x v tuyn in; quy nh th tc kim nh v cng b danh sch t chc iu kin kim nh v an ton bc x v tuyn in i vi i v tuyn in. 1.2. Lut Vin thngLut Vin thng khng quy nh c th v vic kim nh i v tuyn in.1.3. Ngh nh 25/2011/N-CP ngy 06/4/2011Theo quy nh ti iu 34, h thng quy chun k thut vin thng v tn s v tuyn in bao gm cc quy chun v: Thit b u cui. Thit b mng. Thit b o lng tnh gi cc. Kt ni mng vin thng. Dch v vin thng. H tng k thut vin thng th ng. Cht lng pht x ca thit b v tuyn in. An ton bc x v tuyn in ca thit b v tuyn in, thit b ng dng sng v tuyn in, i v tuyn in. An ton tng thch in t ca thit b v tuyn in, thit b vin thng, thit b cng ngh thng tin, thit b ng dng sng v tuyn in v thit b in, in t. Lp t, vn hnh, o kim thit b mng, h tng k thut vin thng th ng, qun l dch v vin thng. Cc quy chun k thut vin thng khc theo quy nh ca B Thng tin v Truyn thng.Quy nh v kim nh i v tuyn in c nu ti Khon 2 iu 35 nh sau:2. Kim nh thit b vin thng l vic o kim, chng nhn hoc cng b s ph hp vi cc quy chun k thut vin thng ca thit b vin thng c lp t trc khi a v hot ng. Vic kim nh thit b vin thng c thc hin nh sau:a) Thit b mng thuc Danh mc thit b vin thng bt buc kim nh do B Thng tin v Truyn thng ban hnh trc khi a vo hot ng phi thc hin vic o kim v chc nhn s ph hp hoc o kim v cng b s ph hp theo quy nh;b) Thit b o lng tnh gi cc thuc Danh mc thit b vin thng bt buc kim nh do B Thng tin v Truyn thng ban hnh trc khi a vo hot ng phi c thc hin vic o kim v chc nhn s ph hp theo quy nh;c) i v tuyn in thuc Danh mc i v tuyn in bt buc kim nh v an ton bc x v tuyn in do B Thng tin v Truyn thng ban hnh trc khi a vo s dng phi thc hin vic o kim v chng nhn s ph hp hoc o kim v cng b s ph hp theo quy nh.1.4. Thng t s 16,17/2011/TT-BTTTT Ngy 30/6/2011 B trng B Thng tin v Truyn thng ban hnh Thng t s 16/2011/TT-BTTTT quy nh v kim nh thit b vin thng v i v tuyn in, Thng t s 17/2011/TT-BTTTT ban hnh Danh mc thit b vin thng v i v tuyn in bt buc kim nh. Hai Thng t ny c hiu lc k t ngy 15/8/2011.Theo quy nh ti Thng t s 17/2011/TT-BTTTT, Danh mc thit b vin thng v i v tuyn in bt buc kim nh gm:Bng 1. Danh mc thit b vin thng v i VT bt buc kim nhS TTTn thit b vin thng,i v tuyn inHiu lc thi hnhChu k kim nh (nm)

1. Trm gc in thoi di ng mt t cng cng (1)T ngy 15/8/20115

2. H thng ghi cc tng i mng vin thng cng cng (2)T ngy 01/7/20125

3. i pht thanh (3)T ngy 01/01/20135

4. i truyn hnh (3)T ngy 01/01/20135

Ghi ch: (1) p dng i vi cc Trm gc in thoi di ng mt t cng cng m trong bn knh 100m tnh t anten bt k ca cc trm gc lp t ti v tr c cng trnh xy dng trong c ngi sinh sng, lm vic.(2) p dng i vi Tng i ca mng vin thng c nh mt t cng cng, Tng i ca mng vin thng di ng mt t cng cng c ghi cc phc v cho vic tnh cc, lp ho n ca dch v in thoi.(3) p dng i vi cc i pht thanh, truyn hnh c cng sut pht cc i t 150W tr ln.Cc khi nim lin quan n vic kim nh i v tuyn in trong Thng t s 16/2011/TT-BTTTT c quy nh nh sau: i v tuyn in bt buc kim nh l mt hoc t hp thit b v tuyn in, bao gm c thit b ph tr km theo c trin khai thc hin nghip v v tuyn in v phi tun th quy chun k thut quc gia v an ton bc x v tuyn in. Kim nh thit b vin thng v i v tuyn in (sau y gi tt l kim nh) l vic o kim v chng nhn thit b vin thng v i v tuyn in ph hp vi quy chun k thut quc gia. Vic kim nh khng thay th v khng lm gim trch nhim ca t chc, doanh nghip i vi cht lng, an ton ca thit b vin thng, i v tuyn in theo quy nh ca php lut.iu 6. Cc trng hp kim nh 1. Kim nh ln u:a) i vi thit b vin thng v i v tuyn in thuc Danh mc thit b vin thng v i v tuyn in bt buc kim nh mi lp t th trc khi a thit b vin thng, i v tuyn in vo khai thc, s dng, t chc, doanh nghip phi tin hnh kim nh theo th tc quy nh ti iu 7 ca Thng t ny. b) i vi thit b vin thng, i v tuyn in thuc Danh mc thit b vin thng v i v tuyn in bt buc kim nh a vo s dng trc ngy hiu lc thi hnh quy nh ti Danh mc thit b vin thng v i v tuyn in bt buc kim nh nhng cha c kim nh, t chc, doanh nghip phi tin hnh kim nh theo quy nh ti iu 9 ca Thng t ny. 2. Kim nh nh k:i vi cc thit b vin thng v i v tuyn in c kim nh, trc ngy ht hn ghi trn Giy chng nhn kim nh t nht ba (03) thng cc t chc, doanh nghip phi tin hnh kim nh li theo th tc quy nh ti iu 7 ca Thng t ny.3. Kim nh bt thng:a) i vi thit b vin thng v i v tuyn in c kim nh nhng c s thay i vt qu mc gii hn an ton cho php ghi trong Giy chng nhn kim nh hoc khi c quan qun l nh nc pht hin thit b vin thng, i v tuyn in khng cn ph hp quy chun k thut quc gia th trong vng ba mi (30) ngy k t ngy c s thay i hoc khi thit b vin thng, i v tuyn in b pht hin khng cn ph hp quy chun k thut quc gia, doanh nghip phi tin hnh kim nh li theo th tc quy nh ti iu 7 ca Thng t ny. b) Trong trng hp thit b vin thng v i v tuyn in c thay i nhng khng vt qu gii hn an ton c T chc kim nh ghi trong Giy chng nhn kim nh th t chc, doanh nghip khng phi kim nh li nhng phi chu trch nhim m bo an ton ca thit b vin thng, i v tuyn in. Trong vng hai mi (20) ngy u tin hng qu, t chc, doanh nghip phi bo co bng vn bn v nhng s thay i trong qu trc n T chc kim nh cp Giy chng nhn kim nh.

CHNG 2. KHO ST TNH HNH THC T TRONG NC V CC I PHT THANH, TRUYN HNH

2.1. Mc tiu pht trin pht thanh truyn hnh n nm 2020Theo Quyt nh s 22/2009/Q-TTg ngy 16 thng 02 nm 2009 ca Th tng Chnh ph ph duyt Quy hoch truyn dn, pht sng pht thanh, truyn hnh n nm 2020, mc tiu pht trin pht thanh v truyn hnh ti Vit Nam trong cc giai on nh sau:* n nm 2010: Ph sng truyn hnh mt t ti 95% dn c; Ph sng pht thanh AM-FM ti 100% dn c, m bo hu ht cc h dn c th thu, nghe c cc knh chng trnh pht thanh qung b.* n nm 2015: Ph sng truyn hnh mt t ti 100% dn c, m bo hu ht cc h dn c th thu, xem c cc chng trnh truyn hnh qung b; Mng truyn hnh cp c trin khai ti 100% trung tm cc tnh, thnh ph trc thuc Trung ng.* n nm 2020: Tng bc trin khai l trnh s ha mng truyn dn, pht sng truyn hnh s mt t ph hp vi iu kin thc t v thit b thu truyn hnh s ca ngi dn trn tng a bn c th. V c bn s ngng pht sng truyn hnh mt t cng ngh tng t chuyn sang pht sng truyn hnh mt t cng ngh s khi 95% s h gia nh c my thu hnh c kh nng thu c cc knh chng trnh truyn hnh qung b bng nhng phng thc truyn dn, pht sng s khc nhau; Ngng vic s dng cng ngh truyn hnh cp tng t trc nm 2020 chuyn hon ton sang cng ngh s vi 100% cc mng cp dc cc tuyn ng, ph chnh ti trung tm cc tnh, thnh ph trc thuc Trung ng c ngm ho; Cng ngh s c p dng rng ri trong truyn dn, pht sng pht thanh; a s cc h gia nh vng su, vng xa, min ni, hi o c nhu cu, c cung cp thit b thu cc knh chng trnh pht thanh, truyn hnh k thut s vi gi c ph hp.2.2. Cng ngh v cc loi pht thanh, truyn hnh ti Vit Nam2.2.1. Cc cng ngh pht thanh, truyn hnh ti Vit NamVit Nam p dng cc cng ngh pht thanh, truyn hnh tin tin trn th gii. Hin ti cc cng ngh c p dng trong h thng pht thanh, truyn hnh Vit Nam bao gm: Pht thanh truyn hnh mt t: pht thanh, truyn hnh k thut tng t (analog) v k thut s (digital). Pht thanh tng t s dng bng tn AM, FM Band I v Band II. Truyn hnh tng t s dng h tiu chun Pal D/K, truyn hnh s s dng h tiu chun DVB-T v DVB-H. Cng ngh truyn hnh s di ng T-DMB (hot ng trn Band III VHF 174-230MHz hoc Band L 1452-1492MHz) cng ang c i Truyn hnh Vit Nam th nghim ti H Ni v TP H Ch Minh. Pht thanh truyn hnh cp hu tuyn. Pht thanh, truyn hnh v tinh. Pht thanh, truyn hnh qua mng di ng v Internet.Theo quy hoch th n nm 2020 h thng i pht thanh, truyn hnh s c hin i ho, c th: Tng bc trin khai l trnh s ha mng truyn dn, pht sng truyn hnh s mt t ph hp vi iu kin thc t v thit b thu truyn hnh s ca ngi dn trn tng a bn c th. V c bn s ngng pht sng truyn hnh mt t cng ngh tng t chuyn sang pht sng truyn hnh mt t cng ngh s khi 95% s h gia nh c my thu hnh c kh nng thu c cc knh chng trnh truyn hnh qung b bng nhng phng thc truyn dn, pht sng s khc nhau. Ngng vic s dng cng ngh truyn hnh cp tng t trc nm 2020 chuyn hon ton sang cng ngh s.2.2.2. Quy hoch bng tn cho h thng pht thanh truyn hnh ti Vit NamTrn c s mc tiu pht trin n nm 2020, Quyt nh s 22/2009/Q-TTg ngy 16 thng 02 nm 2009 ca Th tng Chnh ph quy nh v quy hoch cc bng tn dnh cho h thng pht thanh, truyn hnh mt t ti Vit Nam cng c quy hoch nh sau: Bng MF (526,25 - 1606,5 KHz): pht thanh AM, pht thanh s; Bng I VHF (54 - 68 MHz): pht thanh FM cng sut nh, pht thanh s; Bng II VHF (87 - 108 MHz): pht thanh FM, pht thanh s; Bng III VHF (174 - 230 MHz): truyn hnh tng t, truyn hnh s v pht thanh s; Bng UHF (470 - 806 MHz): truyn hnh mt t cng ngh tng t v s. Theo l trnh s ha th mt phn bng tn ny s c chuyn i sang cho cc nghip v thng tin v tuyn khc; Bng tn L (1.452 - 1.492 MHz): cn c vo iu kin thc t, bng tn ny c th c nghin cu phn b cho pht thanh cng ngh s.2.2.3. Cc cp i pht thanh ti Vit Nama) Pht thanh tng t (tnh theo tng knh tn s), pht thanh s mng n tn: My pht thanh ca i Ting ni Vit Nam. My pht thanh ca i tnh, thnh ph trc thuc Trung ng My pht thanh ca i huyn, th x. My pht thanh do phng, x qun l. My pht thanh ca cc c quan, doanh nghip ngoi ngnh pht thanh -truyn hnh. My pht thanh ca cc c quan, doanh nghip cung cp dch v thng mi. b) Pht thanh tng t c pht km theo cc d liu ph, pht thanh s mng a tn.2.2.4. Cc cp i pht hnh ti Vit Nam : a) Truyn hnh tng t (tnh theo tng knh tn s), truyn hnh s mng n tn My pht hnh ca i Truyn hnh Vit Nam. My pht hnh ca i tnh, thnh ph trc thuc Trung ng. My pht hnh ca i huyn, th x. My pht hnh do phng, x qun l. My pht hnh ca cc c quan, doanh nghip ngoi ngnh pht thanh -truyn hnh. My pht hnh ca cc c quan, doanh nghip cung cp dch v thng mi. b) Truyn hnh tng t c pht km theo cc d liu ph, truyn hnh s mng a tn.2.3. Kho st thc t v cc i pht thanh, truyn hnh trong ncHin nay trn c nc c khong trn 3.000 i pht thanh, truyn hnh vi c s vt cht k thut hin i, ng b, cc i PTTH tnh, thnh ph u c tr s kin c v hin i, mi i u c t nht 1 n 4 my pht sng truyn hnh, mt my pht sng pht thanh FM v my pht sng khcDo vic phn b theo a gii hnh chnh v a hnh khc nhau nhng vn phi m bo yu cu ph sng tt n cc a bn dn c, do mi i pht thanh, truyn hnh c cng sut khc nhau v cao anten khc nhu. Cc s liu kho st v cao, cng sut ca cc i pht thanh, truyn hnh Vit Nam nh c trnh by sau y:2.3.1. i pht thanh AM - Bng MF (526,25 - 1606,5 KHz)Qua kho st cc i pht thanh AM th ch yu cc i ny c cng sut ln v rt ln; cc i ny thuc v cc i pht thanh - truyn hnh cp tnh (29 i) v i Ting ni Vit nam (36 i); trong s 36 i pht thanh ca i Ting ni Vit Nam c 35 i c cng sut t 10KW tr ln; cc i c cng sut nh (02 i) l thuc v cc i pht thanh cp huyn. S liu tng hp v cng sut v cao anten ca cc i pht thanh AM nh sau:Bng 2. Tng hp v cng sut v cao anten ca cc i pht thanh AMTTCng sut pht (W)S lng cao anten (m)

1. 100 130

2. 150 130

3. 1,000 345 - 128

4. 2,000 180

5. 5,000 230 - 65

6. 10,000 2224 - 153

7. 20,000 330 - 186

8. 50,000 1513 - 110

9. 100,000 1116 - 125

10. 200,000 3142 - 199

11. 500,000 490 - 189

12. 2,000,000 190

Tng cng67

2.3.2. i pht thanh AM - bng HF (3 - 30MHz)Cc i pht thanh HF u do i Ting ni Vit Nam qun l. Thc t hin nay c 17 i pht thanh HF lp t ti 4 a im l: tm, Bun ma Thut, tnh c Lc (2 i, 20KW). L Kh, th x Sn Ty, H Ni (8 i 100KW). M tr, T Lim, H Ni (3 i 50KW). X Tn Tin, huyn Chng M, H Ni (4 i 50KW).Cc i pht thanh HF nu trn c cao anten t 12,5m n 45m.2.3.3. i pht thanh FM - Bng I VHF (54 - 68 MHz)Qua kho st thc t 37 i pht thanh FM bng I Vit Nam hin nay th cc i ny u l cc i pht thanh cp phng - x, cng sut t 10W n 60W, cao anten l t 4,5m n 30m.2.3.4. i pht thanh FM - Bng II VHF (87 - 108 MHz)i pht thanh FM c s dng rng ri trn ton quc t cp x, huyn n cp tnh v Trung ng. Cng sut ca cc i pht thanh FM cp huyn, x thng l t 500W tr xung, cc i pht thanh cp tnh v Trung ng c cng sut t 1000W tr ln n 20KW. S liu tng hp v cng sut v cao anten ca cc i pht thanh FM nh sau:Bng 3. Tng hp v cng sut v cao anten ca cc i pht thanh FMTTCng sut pht (W)S lng cao anten (m)

1. T 10 n 1008358 - 105

2. 15011915 - 68

3. 20010515 - 80

4. 2501725 - 100

5. 30020015 - 100

6. 400230 - 36

7. 5006918 - 80

8. 1,0004318 - 125

9. 1,300160

10. 2,0003330 - 100

11. 2,500260 - 100

12. 3,000370 - 100

13. 3,300177

14. 5,0003640 - 125

15. 10,0002540 - 125

16. 20,000830 - 125

17. Tng cng1499

2.3.5. i truyn hnh - Bng III VHF (174 - 230 MHz)Bng 4. Tng hp v cng sut v cao anten ca cc i TH VHFTTCng sut pht (W)S lng cao anten (m)

1. T 10 n 12028410 - 93

2. 150 16312 - 100

3. 200 9515 - 100

4. 250 1125 - 60

5. 300 13918 - 100

6. 500 6622 - 102

7. 700 240

8. 750 1110

9. 800 140

10. 1,000 5410 - 125

11. 2,000 4810 - 125

12. 2,200 1100

13. 2,500 475 - 100

14. 5,000 2750 - 120

15. 10,000 676 - 180

16. 20,000 3110 - 218

17. Tng cng905

2.3.6. i truyn hnh - Bng UHF (470 - 806 MHz)Bng 5. Tng hp v cng sut v cao anten ca cc i TH UHFTTCng sut pht (W)S lng cao anten (m)

1. 20-100930 - 100

2. 150 630 - 60

3. 200 335 - 42

4. 250 290

5. 280 130

6. 300 2210 - 55

7. 500 8220 - 125

8. 1,000 4035 - 125

9. 2,000 1330 - 110

10. 2,500 1100

11. 5,000 4739 - 150

12. 10,000 4440 - 140

13. 20,000 2127 - 135

14. 30,000 2180 - 250

15. 50,000 2180

16. Tng cng276

2.3.7. i truyn hnh k thut s pht trn knh 6 n knh 59Hin ti Vit Nam c 3 n v cung cp dch v truyn hnh k thut s l Tp on Truyn thng a phng tin (VTC), i Truyn hnh Vit Nam (VTV) v Cng ty c phn Nghe nhn Ton Cu (AVG). VTC ph sng 39/63 tnh, thnh ph trn c nc, cng ngh ch yu l DVB-T; AVG c 6 i pht sng ti H Ni v TP H Ch Minh vi cng ngh l DVB-T, VTV c 7 i pht sng ti 7 tnh l H Ni, Nam nh, Ngh An, Lo Cai, Ph Yn, Tha Thin Hu, Thanh Ho. S liu tng hp v cng sut v cao anten ca cc i truyn hnh k thut s nh sau:Bng 6. Tng hp v cng sut v cao anten ca cc i TH KTSTTCng sut pht (W)S lng cao anten (m)

1. 1002220 - 90

2. 150660 - 80

3. 2003230 - 125

4. 2502100

5. 300260

6. 400640 - 110

7. 1,0002540 - 125

8. 2,0001230

9. 5,000275 - 100

10. 6,000580 - 230

11. 10,0007100 - 180

Tng cng110

CHNG 3. NGHIN CU CNG TC TIU CHUN HO CA CC NC V CC T CHC QUC T3.1. Tng quan v nh hng ca sng v tuyn[footnoteRef:1] [1: TCVN 3718-1:2005 - Qun l an ton trong bc x tn s radio - phn 1.]

3.1.1. Bn cht ca bc x RFBc x RF sinh ra mc cao trong ngnh pht thanh truyn hnh qung b. Vic sinh ra v lan truyn trng RF l c ch m nh tt c cc tn hiu qung b c truyn n khn, thnh gi. Ngnh qung b cng sinh ra cc trng ny mc cao hn hn ngnh vin thng do s dng cc tn s thp hn v i hi vng ph sng rng hn nhiu.

Hnh 1. Ph sng in tBc x RF bao gm c trng in v trng t. Vic m rng ca c hai trng cn c bit n trong mi lin quan vi cc hiu ng sinh ra trong c th. Trong trng gn (gn vi ngun bc x) cn phi o c trng in v trng t, tuy nhin, trong trng xa, quan h gia hai trng l quan h tuyn tnh nn ch cn o mt trng.Bc x tn s radio l bc x khng ion ha. Bc x RF khng lm thay i cu trc phn t ca c th theo cch nh bc x ion ha.3.1.2. nh hng n sc khenh hng trc tin ca vic phi nhim trong trng RF cao l tng nhit c th. Tuy nhin, nh hng lu di ca vic tng nhit ny vn cn ang c xem xt.nh hng th hai r rt hn n sc khe l bng RF, xy ra khi tip xc vi chn t anten, fi hoc b phn ghp ni c in p RF cao.a) nh hng v nhitTrong trng RF c th chia thnh cc di sau: Mt dng nng lng cao, thng l c hn 10mW/cm2, ti xut hin hiu ng v nhit r rt; Mt dng nng lng trung bnh, t 1mW/cm2 n 10mW/cm2, ti o c cc hiu ng nhit yu nhng ng k; v Mt dng nng lng thp, di 1mW/cm2, khng tn ti cc hiu ng nhit nhng c cc hiu ng khc.Khi c th hp th bc x RF, lng bc x ny s chuyn thnh nhit dn n tng nhit ca c th. Lng nng lng m c th hp th v sau chuyn thnh nhit ph thuc vo mt s yu t. Cc yu t l: Cng trng; Tn s bc x; Kch thc v hnh dng con ngi; Hng ca trng in v trng t so vi trc dc ca c th; v Ngi c ng trn mt t hay khng.Phn ng to ra trong ngi ty thuc vo v tr c phn b nhit trn c th v iu ny phu thuc vo: Th tch v loi m chiu (ngha l vng c th ca c th b bc x n); C ch lm mt ca c th; v iu kin mi trng (v d thi tit nng hay lnh).Vic hp th bc x vo c th c quy nh theo mc hp th ring (SAR - l mc theo thi gian m nng lng RF truyn vo mt n v khi lng sinh hc, biu th bng Ot trn kilgam W/kg). Mc SAR trung bnh theo tn s i vi con ngi c v trn biu di y.

Hnh 2. Hp th bc x RF ca c th theo tn sCc hiu ng sinh hc ca vic gia nhit ny c quan st trn ng vt ( mc phi nhim rt cao) v bao gm cc thng tn cc b phn c th, thn nhit tng rt cao v cht. Phi nhim nhiu tn s vi sng cng c th gy thng tn cho mt, gy c nhn mt v cc thng tn vng mc lm hng mt.Cc th nghim trn ng vt, ch yu l loi gm nhm v ng vt linh trng cho thy ngng SAR i vi cc hiu ng nhit nguy him l khong 4W/kg. Cc hiu ng nhit cng xy ra rmc SAR thp hn v trong khi cc hiu ng ny cha c tc hi r rt nhng chng c th coi l ng k.Gia nhit cc b nhiu b phn khc nhau ca c th s xy ra ty thuc vo tn s ca bc x nh cho trn hnh 2.C hai c ch c bn m c th ngi c th phi chu s hp th nng lng RF trong thc tin ngnh qung b. Trng hp th nht l khi c th ngi nm trong trng c chnh lch in th ng k. V d nh ngi vn hnh c th vo trong mt my pht hoc hp u ni anten v b t gia mt linh kin ln c in tch cao v d nh cun cm RF v mt khung kim loi c in th thp hoc in th t.Trng hp th hai l con ngi tip cn hoc t trong trng in t ca h thng bc x, c th ngi ng vai tr nh mt cc thng ng v hp th nng lng nh mt anten thu thng ng. Trong trng hp ny, c th c cc thuc tnh ging nh mt anten thng ng, bao gm tr khng c trng, in tr nn v in khng ti im tip xc vi mt t.Chiu cao ca c th ngi v tn s lin quan s xc nh kh nng ca c th ngi nh mt b tip nhn nng lng v trong hu ht cc v d v qung b, chiu cao v in ca con ngi s nh hn so vi bc sng. V l do ny nn "tr khng nn" gia c th ngi v t thng c in dung cao v do vic cch ly vi t bng cch mang giy cch in s lm gim i cht dng in chy xung t.b) Bng RFBng RF c th xy ra do h quang hnh thnh gia mt b phn ca c th ngi v mt phn t ca h thng pht c in th cao so vi t. Bng cng c th xy ra do dng in cm ng trong c th khi phi nhim trong trng t do.Ni chung, bng RF xy ra trn bn tay ngi khi tip xc vi nhiu phn t. Khi dng in RF chy qua c th ngi xung t. Khi h quang hnh thnh th gy bng su v rt lu lnh. Trong mt s trng hp b bng nng dn n hng c chn ln tay.Bng RF cng c th xy ra khi tip xc vi cc phn t khng dn hng. V d mt on dy cng gn mt anten bc x AM/FM c th c dng in cm ng trong v to in th gy bng khi tip xc vi dy.Ngng thu di trung tn in hnh l t 25mA n 40mA, trong khi dng in khong 90mA c th gy git. trnh b bng RF do mt dng in vt qu quy nh, mc 100mA thng c chp nhn l gii hn i vi dng in chy qua chi bt k ca c th ngi. ng h o dng in loi Holaday HI-3701 v HI-3702 c thit k o dng in cm ng trong c th.Do , nh ng gia nhit ni chung trn c th khng ch xt n nh hng v sc khe m cn cn c ch c bit n an ton ca con ngi nhng ni c th xy ra bng RF. Thng thng, nu mt ngi trong trng thi c th b bng RF th ngi cng ang trong trng RF cao v khu vc cn phi b cm.3.1.3. C s xy dng mc phi nhim ln nht i vi bc x RFa) Gii thiuMc ch ca vic xy dng mc phi nhim ln nht i vi bc x RF l bo v sc khe con ngi khi cc hiu ng c hi tim n ca vic phi nhim trong trng in t RF.Cc ti liu khoa hc ca T chc Y t th gii (WHO 1993) v di tn t 300Hz n 300GHz lm c s khoa hc xy dng cc gii hn phi nhim.WHO cng a ra cc hng dn quc t v cc gii hn phi nhim c Hip hi Bo v Bc x quc t (IRPA 1988) cng b. V cc hng dn quc t ch cp n di tn s t 100kHz n 300GHz nn y ban m rng tn s xung cn 3kHz. Tuy nhin, ti cc tn s t 400MHz n 2GHz, phng php lun c th dn n s tng tch ly cc mc dn xut v sau dn n mc khng i vi mi tn s. b) Dn cGii hn phi nhim c th gn vi dn c ni chung hoc cc nhm ngi c th. Cc nhm ny c coi l t nhiu nhy vi cc nh hng c hi cho sc khe do RF gy ra, v c th hoc khng phi chu cc kim tra v y t. Dn c b phi nhim do ngh nghip gm nhng ngi trng thnh chu phi nhim trong cc iu kin khng ch, c hun luyn nhn bit nhng nguy him tim n v thc hin cc bin php phng nga thch hp. Khong thi gian phi nhim do ngh nghip c gii hn thi gian mt ngy lm vic hoc mt ca lm vic trong vng 24h v khong thi gian ca cuc i lm vic.Cng chng (nhng dn c chu phi nhim khng do ngh nghip) gm nhng ngi mi tui v tnh trng sc khe khc nhau. Phm vi cng hng l khc nhau gia ngi trng thnh v tr em v v vy l s phn b mc hp th nng lng RF trong cc b phn khc nhau ca c th. Mt s ngi c th c bit nhy cm vi bc x RF.Trong nhiu trng hp, mt s dn c chu phi nhim khng do ngh nghip khng nhn thy l ang c phi nhim. Dn c chu phi nhim khng do ngh nghip c th phi chu phi nhim 24h mt ngy, v trong sut cuc i, v khng th thc hin cc bin php phng nga chng RF, c th l bng v sc.Cc xem xt trn y l l do chp nhn cc mc phi nhim c s (dn xut) i vi phi nhim khng do ngh nghip thp hn i vi dn c b phi nhim do ngh nghip.Mc phi nhim thp hn i vi dn c chu phi nhim khng do ngh nghip ph hp vi cc khuyn co ca IRPA, ICNIRP v cc t chc tiu chun ln khc trn th gii.c) Xem xt c bni vi cc tn s trn 10MHz, gi tr SAR trung bnh trn ton c th ngi (WBA-SAR) c chn lm i lng thit lp cc gii hn phi nhim c s, v chp nhn cc gi tr khc nhau i vi dn c chu phi nhim do ngh nghip v khng do ngh nghip. Cc gii hn i vi dn c chu phi nhim do ngh nghip v khng do ngh nghip c rt ra ch yu t s ph thuc vo tn s ca WBA-SAR v c sa i bi cc xem xt v s hp th nng lng RF khng ng nht trong cc b phn ca c th, tc l, ca gi tr SAR nh theo khng gian c ly trung bnh trn mi 10g m.SAR l i lng thch hp nh gi hiu ng sinh hc ty thuc vo tng nhit kt hp vi s hp th nng lng RF. Tuy nhin, do ph thuc vo cng trng in bn trong nn SAR cng c th c s dng nh gi cc nh hng ph thuc vo cng trng in trong cc m. Do , mc d cc gii hn phi nhim ch yu da trn cc xem xt v nhit i vi di tn s trn 10MHz, nhng mc ch bo v chng cc nh hng khng nhit cng c xem xt.Mc ch khc l loi b cc nguy him ca sc v bng RF cho cng chng ni chung. Php o liu lng cho thy rng trong cc iu kin nht nh, SAR cc b ti bn chn v bn tay, c bit l ti mt c chn v c tay, c th vt qu WBA-SAR khong 300 ln mt s tn s nht nh. Do , cc mc phi nhim do ngh nghip c thit lp gim hin tng sc nh v phn ng t ngt. Di 10MHz, cng trng t khng nhp nh t b hn ch hn cng trng in v n khng gp phn vo nguy him sc hoc bng RF; l do chnh quan tm l gii hn ca cng trng in trong phi nhim do ngh nghip.Da vo cc xem xt v c ch tng tc ng sau cc hiu ng sinh hc, phi tnh n c tn s v mt . Cc nh hng ph thuc nhit c c th ha v c th s dng lm c s cho cc gii hn phi nhim. Bng chng v c ch khng nhit ca cc hiu ng sinh hc khng c b qua, nhng khng c nh hng khng nhit c ghi li no cho thy l c tc ng c hi cho sc khe.d) Hp th nng lngTng lng hp th, phn b v t l hp th nng lng in t trong c th sng l mt hm ca nhiu yu t. Cc i lng nh cng trng in bn trong (V/m), dng cm ng trong c th (A), mt dng in cm ng (A/m2) v mc hp th ring SAR (W/kg) c lin quan vi nhau. SAR thng c s dng so snh cc hiu ng sinh hc trong cc iu kin phi nhim khc nhau. SAR c th c s dng xc nh s phn b nng lng (c hp th) bn trong. Vi mt s hn ch, SAR cng c th c s dng nh gi tc thay i ca nhit theo thi gian vi iu kin l bit cc c tnh trao i nhit, k c p tuyn iu chnh nhit ca c th con ngi hin ang c xem xt. SAR ph thuc vo cc yu t sau: Cc thng s ca trng ti; tn s, mt (mt dng nng lng), phn cc v cu hnh gia i tng ngun (trng gn v trng xa); Cc c tnh ca c th b phi nhim; kch thc, hnh th bn trong v bn ngoi, cc c tnh in phn ca cc lp m khc nhau trong i tng nhiu lp khng ng nht (v d nh c th ngi); Cc hiu ng mt t v hiu ng phn x t cc i tng khc trong trng, v d nh cc b mt kim loi gn c th b phi nhim.Khi trc dc ca c th ngi song song vi vc t trng E ca sng in t (gi l phn cc E) th tc hp th nng lng sng in t trn ton c th t n gi tr ln nht (gi l cng hng). S cng hng theo khng gian t do xut hin khi chiu di trc dc ca c th vo khong 0,4. Lng nng lng hp th ph thuc vo mt s yu t, k c kch thc ca ngi b phi nhim.Nh th hin trn hnh 3, mt ngi cao 1,74m, nu khng c tip t, s c cng hng nng lng hp th tn s gn 70MHz. Nhng ngi nh hn v tr em c s cng hng nng lng hp th tn s vt qu 100MHz. Nhng ngi cao hn c tn s hp th cng hng thp hn 70MHz. Ti tn s 2450MHz, mt ngi cao 1,74m s hp th khong 50% nng lng in t ti.

Hnh 3. Mt dng nng lng m gii hn SAR trn ton b c th ngi n 0,4W/kg. c th hiu thm tm quan trng ca khu vc cng hng nng lng hp th, cn hiu rng phi nhim ca ngi cao 1,7m trong trng tn s 70MHz cc iu kin hp th ln nht s tng ln 7 ln so vi mc hp th trong trng 2450 MHz. Do cc gi tr ca gii hn phi nhim phi da trn s ph thuc ca con ngi vo tn s trn ton di tn i vi kch thc c th. Nu hn ch phi nhim RF mc 0,4W/kg th mt dng nng lng dn xut tng ng vi gii hn ny c th hin trn hnh 3.Trong di tn s trn 10MHz, khi mc cng trng in v trng t lm vic c ly t gii hn c s WBA-SAR th c th xt ring s ng gp ca cc thnh phn trng in v trng t vo WBA-SAR. Trong trng hp xu nht, nng lng ghp ni do phn cc E ca trng in chim u th hn v WBA-SAR t n gi tr ln nht l khong 1,2 x 10-2W/kg tn s 20MHz i vi ngi trng thnh, gy, chu phi nhim 10W/m2. Vic ghp nng lng t ng gp ca ring trng t khng th vt qu mc SAR ny. V vy, c th thay i cc mc lm vic dn xut i vi cng trng in v trng t trong cc trng hp khi s phi nhim chim u th hn t cc thnh phn trng in hoc trng t hoc mt trong cc thnh phn ny mt cch n l.p tuyn sinh hc ca phi nhim trong trng RF khng ch n thun ph thuc vo mt cc trng bn ngoi c th, m cn ph thuc vo cc trng bn trong c th c lin quan ti gi tr SAR ly trung bnh trn ton c th v s phn b bn trong c th con ngi. S phi nhim trong trng in t ng nht (sng phng) thng gy ra s hp th v phn b nng lng khng ng nht cao trong c th. Gi tr SAR trung bnh theo khng gian l phng tin thun li nh gi mi quan h gia hiu ng sinh hc v phi nhim RF v so snh gia cc hiu ng cc iu kin phi nhim khc nhau.i vi cc tn s thp khong t 100kHz n 10MHz, c ch tng tc chim u th l cm ng ca dng in v trng in trong c th con ngi. Do , cc gii hn phi bo v chng li cc nh hng trc tip ln c th con ngi v d nh kh nng dng in gy ra s kch thch cc c v h thn kinh.Ngoi ra, cc tn s thp hn, phi tnh n cc nh hng gin tip c th xy ra. Cc nh hng ny bao gm sc v bng RF gy ra do tip xc vi scc vt dn tch in trong trng.e) Mi quan h vi sc kheWHO (1993) cng b xem xt v nh gi chi tit ca cc ti liu khoa hc da vo a ra cc gii han phi nhim. Cc nh gi c thc hin t cc bo co khoa hc v vic c cc hiu ng sinh hc gy nguy him cho sc khe hay khng. Phn ng trn cc con vt th nghim cho thy rng chng l cc sinh vt nhy cm nht trc cc nh hng c hi n sc khe (v d nh ngng hot ng, gim kh nng hot ng, gim sc chu ng, nhn thy c trng phi nhim v c biu hin khng thoi mi). WHO kt lun rng phi nhim cao (di 1h) trong trng in t hp th trong ton b c th vi mc SAR trung bnh nh hn 4W/kg th khng gy ra nh hng c hi n sc khe trn cc con vt th nghim. Ph hp vi cc tiu chun khc v c th l vi tiu chun c IRPA xut bn nm 1988 v ICNIRP xut bn nm 1996, i vi phi nhim do ngh nghip, gi tr SAR trung bnh cho php trn ton c th gim i mi ln (tc l 0,4W/kg) l chp nhn c.S c bo v chng cc nh hng RF nu cc gii hn SAR c s c ly trung bnh trn 10g m. Ngoi ra, hn ch dng in gia c th ngi v t v dng in tip xc gi tr 200mA l bin php trnh t nng qu mc c tay hoc mt c chn. Trn c s cc s liu hin c, cc hn ch ny v cc mc phi nhim dn xut cn thch hp ngn nga s hp th nng lng RF qu mc trong b phn bt k ca c th.Khng tn ti cc iu kin phi nhim ngng i vi cc hiu ng sinh hc c th p dng cho mi di tn s v cho mi tn s iu bin c th c. Do , cc h s an ton phi c gn lin vi cc mc phi nhim khng ch tnh n s thiu s liu khoa hc m cn tnh n mi iu kin c th xy ra phi nhim. Cc tham s c xem xt khi xy dng h s an ton gm: S hp th nng lng in t ca nhng ngi c kch thc khc nhau, lin quan c bit n hp th nng lng cng hng trn ton b hoc mt phn c th; Thiu kin thc v mi quan h gia SAR nh v hiu ng sinh hc; iu kin mi trng - cc gii hn phi nhim cn c bo v trong cc iu kin bt li ca nhit , m v lu thng khng kh; Phn x tp trung hoc phn tn ca trng ti dn n tng s hp th; Cc phn ng khc nhau c th c ca con ngi khi ung thuc; Cc nh hng kt hp c th c ca nng lng in t RF vi cc cht ha hc hoc vt l khc trong mi trng; Cc nh hng c th c ca trng vi sng iu bin ln h thn kinh trung ng v kh nng tn ti ca khe h "cng sut" v "tn s" i vi cc nh hng ny; Cc nh hng khng nhit c th c.i vi tt c cc phi nhim, chu k ly trung bnh theo thi gian l 6 pht, v iu ny tng i ng nht vi tt c cc tiu chun hin hnh.Trong di tn s thp hn 10MHz, dng in cm ng s lm tng c ch tng tc chim u th. Ti cc phi nhim RF cao trong di tn t 3kHz n 10MHz, c th gy ra mt dng in kch thch ln cc m thn kinh v m c.Cc gii hn c thit lp m bo trnh cc nh hng ny. Mc d sc RF thng to ra cc nh hng trong phm vi t kh chu n bng nghim trng cho cc m, nhng tnh hung c th pht sinh khi sc v bng nh vy gy ra cc tai nn nghim trng hn. Cc php o trc tip dng in gia ngi v t hoc vt th, s dng ampe-mt n gin l kim tra dng in ln nht c th xut hin trong trng hp c th. Dng in nh hn 50mA c th c coi l an ton. i vi phi nhim khng do ngh nghip di 10MHz, cc gii hn phi nhim cn nh khng th xut hin sc RF, v s l khng hp l nu yu cu nhm ngi ny phi thc hin cc bin php phng nga trnh cc sc nh vy.WHO xem xt cc s liu lin kt phi nhim trng in v trng t lm tng ri ro gy ung th hoc d dng bm sinh trong cc c dn b phi nhim nhng cha kt lun v chng minh c rng phi nhim trng RF gy ra hoc thc y ung th, hoc pht trin cc ung th ang tn ti. Cc d liu ny khng th s dng thit lp cc gii hn phi nhim.f) Mc phi nhim dn xutCc gii hn v mc hp th ring SAR trn thc t l rt kh o, o c SAR th phi th nghim hoc lp m hnh ton hc chng t s ph hp vi cc gii hn SAR nh theo khng gian. Cc php o hoc php ton nay phi da trn c s mi quan h khng gian thng thng gia anten ca thit b v ngi s dng, trong th hin khi lm vic bnh thng, anten hoc cc kt cu bc x khc t cch c th ca ngi s dng mt khong nh hn 20cm.Trong nhiu trng hp khng th o c SAR. Trn thc t cc tham s nh mc dn xut ca cng trng in (E) v trng t (H) hiu dng, mt dng nng lng sng phng (S) tng ng v dng in cm ng (I) chy qua c th ngi l hm s ca tn s v c th d dng o c v s dng chng t s ph hp.3.2. IEEE (M)Nm 1960, Hip hi Tiu chun M (American Standards Association) bt u thc hin d n xy dng cc tiu chun an ton bc x di s bo tr ca B Hi qun v IEEE.Trc nm 1988, b tiu chun C95 do U ban Tiu chun c cng nhn C95 (Accredited Standards Committee C95 - ASC C95) pht trin v c trnh ANSI chp thun v ban hnh thnh b tiu chun ANSI C95. Trong khong thi gian 1988 n 1990, U ban ny c chuyn i thnh U ban phi hp tiu chun 28 (Standards Coordinating Committee 28 - SCC 28) di s bo tr ca Ban tiu chun IEEE. ph hp vi chnh sch ca IEE, C95 c banh hnh v pht trin nh l b tiu chun ca IEEE v cng c trnh ln ANSI c cng nhn.Lnh vc hin ti ca IEEE SCC 28 l Pht trin cc tiu chun v an ton trong vic s dng nng lng in t trng trong di tn t 0 Hz n 300 GHz lin quan n s nh hng tim nng ca nng lng ny gy ra phi nhim n con ngi, cc vt liu d bay hi v cc thit b d n. Lnh vc ny khng bao gm cc bc x hng ngoi, nh sng nhn thy, tia t ngoi hoc bc x ion ho. U ban IEEE SCC 28 c 5 tiu ban v:1. K thut, th tc, thit b o c v tnh ton.2. Thut ng, n v o kim v thng tin v nguy him.3. Mc an ton phi nhim ca ngi trong khong 0 Hz n 3 kHz.4. Mc an ton phi nhim ca ngi trong khong 3 kHz n 300 GHz.5. Mc an ton i vi cc thit b n, thit b in t.U ban IEEE SCC 28 ban hnh 3 tiu chun, 1 hng dn v 4 khuyn ngh. Cc phin bn hin ti bao gm:1. IEEE Std C95.1-2005 - Tiu chun v an ton phi nhim i vi ngi trong cc trng in t tn s radio, di tn s t 3 kHz n 300 GHz (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz). 2. IEEE C95.2-1999 - Tiu chun v cc k hiu tn s v tuyn in v dng in (IEEE Standard for Radio Frequency and Current Flow Symbols).3. IEEE Std C95.3-2002 - Khuyn ngh v o kim v tnh ton cc trng in t tn s radio lin quan n phi nhim ca con ngi, di tn s t 3 kHz n 300 GHz (IEEE Recommended Practice for the Measurement and Computations of Radio Frequency Electromagnetic Fields with Respect to Human Exposure to such Fields, 100 kHz to 300 GHz).4. IEEE Std C95.4-2002 - Khuyn ngh v cch xc nh khong cch an ton t anten pht sng v tuyn bng cch s dng kp n trong cc qu trnh vn hnh d gy n (Recommended Practice for Determining Safe Distances from Radio Frequency Transmiting Antennas When Using Electric Blasting Caps During Explosive Operations).5. IEEE Std C95.5-2002 - Khuyn ngh v o kim cc trng in t gy nguy him - tn s radio v vi ba (IEEE Standard Recommended Practice for the Measurement of Hazardous Electromagnetic Fields - RF and Microwave).6. IEEE Std C95.6-2002 - Tiu chun v an ton phi nhim trng in t, di tn t 0 n 3 kHz (IEEE Standard for Safety Levels With Respect to Human Exposure to Electromagnetic Fields, 0-3 kHz).7. IEEE Std 1460-1996 - Hng dn v o kim cc trng in v trng t gn nh tnh (IEEE Guide for the Measurement of Quasi-Static Magnetic and Electric Fields).8. EEE Std C95.7-2007 - Khuyn ngh v chng trnh an ton tn s v tuyn in, 3 kHz n 300 GHz (IEEE Recommended Practice for Radio Frequency Safety Programs, 3 kHz to 300 GHz).Tiu chun C95.1-2005:Tiu chun IEEE Std C95.1-2005 a ra cc mc gii hn phi nhim i vi cc trng in v trng t cho ton b c th v trong khong thi gian trung bnh. Cc gii hn c th hin theo gi tr mc phi nhim cc i cho php (Maximum Permissible Exposure - MPE). Ngoi ra tiu chun cng a ra gii hn v dng in cm ng v dng in tip xc.Cc mc gii hn an ton cho php trong mi trng c kim sot c quy nh trong bng sau:Bng 7. Bng quy nh gii hn MPE ca tiu chun C95.1-2005 i vi mi trng c kim sotDi tn (MHz)RMS cng trng in (E)a (V/m)RMS cng trng t (H)a (A/m)RMS mt cng sut (S) E-field, H-field (W/m2)Thi gian o trung bnh |E|2, |H|2, hoc S (pht)

0,1-1,0184216,3/fM(9000, 100000/fM2)b6

1,0-301842/fM16,3/fM(9000/fM2, 100000/fM2)b6

30-10061,416,3/fM(10, 100000/fM2)b6

100-30061,40,163106

300-3000--fM/306

3000-30000--10019,63/fG1,079

30000-300000--1002,524/fG0,476

Ghi chfM l tn s tnh bng MHz, fG tn s tnh bng GHz

a i vi cc phi nhim ng nht trn ton b c th, nh phi nhim sng phng trng xa xc nh th cng trng phi nhim v mt cng sut c so snh vi cc gi tr MPE trong bng trn. i vi cc phi nhim khng ng nht, gi tr trung bnh ca cc trng phi nhim, l gi tr c xc nh bng trung bnh bnh phng ca cc cng trng hoc trung bnh ca cc mt cng sut trn mt din tch tng ng vi mt ct ng ca c th ngi (vng c lng), hoc mt din tch nh hn tu thuc vo tn s, c so snh vi cc gi tr MPE trong bng trn.

b cc gi tr mt n cng sut sng phng tng ng thng c s dng hn trong vic so snh vi cc gi tr MPE di tn s cao v c hin th trn mt s thit b o.

Hnh 4. Biu biu din gi tr MPE trong mi trng c kim sotCc mc gii hn an ton cho php trong mi trng khng kim sot c quy nh trong bng sau:Bng 8. Bng quy nh gii hn MPE ca tiu chun C95.1-2005 i vi mi trng khng c kim sotDi tn (MHz)RMS cng trng in (E)a (V/m)RMS cng trng t (H)a (A/m)RMS mt cng sut (S) E-field, H-field (W/m2)Thi gian o trung bnh |E|2, |H|2, hoc Sb (pht)

0,1-1,3461416,3/fM(1000, 100000/fM2)c66

1,34-3823,8/fM16,3/fM(1800/fM2, 100000/fM2)fM2/0,36

3-30823,8/fM16,3/fM(1800, 100000/fM2)306

30-10027,5158,3/fM1.668(2, 9400000/fM3,336)300,0636fM1,337

100-40027,50,072923030

400-2000--fM/20030

2000-5000--1030

5000-30000--10150/fG

30000-100000--1025,24/fG0,476

100000-300000--(90fG-7000)/2005048/[(9fG-700)fG0,476]

Ghi chfM l tn s tnh bng MHz, fG tn s tnh bng GHz

a i vi cc phi nhim ng nht trn ton b c th, nh phi nhim sng phng trng xa xc nh th cng trng phi nhim v mt cng sut c so snh vi cc gi tr MPE trong bng trn. i vi cc phi nhim khng ng nht, gi tr trung bnh ca cc trng phi nhim, l gi tr c xc nh bng trung bnh bnh phng ca cc cng trng hoc trung bnh ca cc mt cng sut trn mt din tch tng ng vi mt ct ng ca c th ngi (vng c lng), hoc mt din tch nh hn tu thuc vo tn s, c so snh vi cc gi tr MPE trong bng trn.

b Ct bn tri l thi gian trung bnh p dng i vi |E|2, ct bn phi l thi gian trung bnh p dng i vi |H|2. i vi cc tn s ln hn 400MHz th thi gian trung bnh ch p dng i vi mt cng sut S.

c Cc gi tr mt cng sut sng phng tng ng thng c s dng hn trong vic so snh vi cc gi tr MPE di tn s cao v c hin th trn mt s thit b o.

Hnh 5. Biu biu din gi tr MPE trong mi trng khng kim sotCc trng hp ngoi tr v vic ni lng gii hn i vi phi nhim tng phn trn c thTrong mt s trng hp c th, ch c cch thc t duy nht gii quyt cc vn v phi nhim trong cc trng khng ng nht v cc thit b cng sut thp bng phng php ngoi tr cho php cc gi tr cng trng cc b (v mt cng sut sng phng tng ng, nu p dng c) c th vt qu gi tr MPE quy nh chung.Vic ngoi tr c da trn cc xem xt sau: Cc quy nh chung ca tiu chun khng c vi phm. Mc SAR trung bnh trn ton b c th ngi khi b phi nhim cc b khng c vt qu mc 0.4 W/kg v 0.08 W/kg tng ng vi mi trng c kim sot v mi trng khng c kim sot. Cc nghin cu trc y cho thy cc gi tr SAR nh trong c th sinh hc c th cao hn mc SAR trung bnh t 10 n 20 ln. Nu gi tr nh ca trung bnh bnh phng cng cc trng v mt cng sut tng ng l ph hp vi quy nh ni lng i vi tng phn c th th khng c vi phm cc quy nh chung v MPE i vi phi nhim tng phn c th hoc phi nhim cc trng khng ng nht. Cc nghin cu trong phng th nghim cho thy cc thit b v tuyn cm tay cng sut thp (trong phn t pht x cch c th ngi trn 2,5cm) th mc gy phi nhim i vi ngi s dng khng vt qu tiu chun trong mi trng c kim sot hoc i vi nhng ngi khc xung quanh ngi s dng khng vt qu tiu chun trong mi trng khng c kim sot nu cng sut bc x 7W ti tn s t 100 kHz n 450 MHz v 7(450/f) W ti tn s t 450MHz n 1500 MHz. Hn na cc nghin cu ny cng cho thy cc thit b tng t s khng gy ra mc phi nhim cho ngi s dng vt qu tiu chun trong mi trng khng c kim sot nu cng sut bc x 1,4W ti tn s t 100 kHz n 450 MHz v 1,4*(450/f) W ti tn s t 450MHz n 1500 MHz.Do , cc trng hp ngoi tr trn c a vo tiu chun ny cho php mt s trng hp c th vt qu gi tr MPE nu m bo rng: Mc SAR trung bnh trn ton b c th v trong mt khong thi gian thch hp khng vt qu 0,4 W/kg v 0,08 W/kg tng ng vi mc phi nhim trong mi trng c kim sot v mi trng khng c kim sot; v Gi tr SAR nh trung bnh trn 1g m bt k (c nh ngha l mt khi m hnh lp phng) trn c th trong mt khong thi gian thch hp khng vt qu 8 W/kg (trong mi trng c kim sot) v 1,6 W/kg (trong mi trng khng c kim sot) v trn 10g m bt k (c nh ngha l mt khi m hnh lp phng) c tay, mt c chn, tay v chn (c nh ngha l mt khi m hnh lp phng) trong mt khong thi gian thch hp khng vt qu 20 W/kg (trong mi trng c kim sot) v 4 W/kg (trong mi trng khng c kim sot). Gii hn 20 W/kg i vi c tay v mt c chn cho php s hp th cao hn trong cc m mm to ra bi cc dng in cm ng chy qua cc xng ny v cc vng mt ct hp. 3.3. Lin minh Vin thng quc t (ITU)Lin minh Vin thng quc t (ITU) c mt s tiu chun, khuyn ngh v phng php tnh ton, nh gi v mc phi nhim ca cc i pht v tuyn in gy ra, v d nh: ITU-T Recommendation K.52 (2004), Guidance on complying with limits for human exposure to electromagnetic fields. ITU-T Recommendation K.61 (2003), Guidance to measurement and numerical prediction of electromagnetic fields for compliance with human exposure limits for telecommunication installations. ITU-T Recommendation K.70 (2007), Mitigation techniques to limit human exposure to EMFs in the vicinity of radiocommunication stations.Khuyn ngh ITU-T K.70 c a ra mt phng php n gin v tnh ton cc khong cch tun th (compliance distances) i vi cc i pht trong cc di tn s t 1 MHz n 300 GHz nh sau:Bng 9.Cng thc tnh ton khong cch tun th ti thiu t anten ca i pht p dng i vi khu vc cng cngDi tnKhong cch

1 to 10 MHz

10 to 400 MHz

400 to 2000 MHz

2000 to 300000 MHz

rkhong cch ti thiu tnh t anten, mftn s, MHzerpcng sut bc x hiu dng theo hng c h s tng ch ln nht, Weirpcng sut bc x ng hng tng ng theo hng c h s tng ch ln nht, W

Bng 10.Cng thc tnh ton khong cch tun th ti thiu t anten ca i pht p dng i vi khu vc phi nhim do ngh nghipRadio frequency rangeOccupational exposure

1 to 10 MHz

10 to 400 MHz

400 to 2000 MHz

2000 to 300000 MHz

rkhong cch ti thiu tnh t anten, mftn s, MHzerpcng sut bc x hiu dng theo hng c h s tng ch ln nht, Weirpcng sut bc x ng hng tng ng theo hng c h s tng ch ln nht, W

3.4. Chu uHi ng ca Lin minh Chu u (THE COUNCIL OF THE EUROPEAN UNION) ban hnh khuyn ngh s 1999/519/EC ngy 12/7/1999 v gii hn phi nhim trng in t i vi khu vc cng cng trong di tn s t 0 Hz to 300 GHz. Theo khuyn ngh ny, tu theo tn s, cc i lng vt l sau y s dng xc nh cc gii hn c bn v trng in t: Trong di tn s t 0 n 1Hz, cc gii hn i vi mt thng lng t trng ca cc trng tnh (0Hz) v mt dng in ca cc trng bin thin n 1Hz c s dng ngn chn nh hng n mch mu v h thn kinh trung ng. Trong di tn t 1Hz n 1MHz, cc gii hn c bn c p dng i vi mt dng in ngn chn nh hng n chc nng ca h thn kinh. Trong di tn t 100kHz n 10GHz, cc gii hn c bn v SAR c p dng ngn chn nh hng nhit trn ton b c th v s lm nng cc b qu mc ca cc m. Trong di tn s t 100 kHz n 10 MHz, cc gii hn p dng i vi c SAR v mt dng in. Trong di tn t 10GHz n 300GHz, cc gii hn c bn v mt cng sut c p dng ngn nga s lm nng cc m ngoi da hoc gn lp da.Cc gii hn c bn i vi trng in, trng t v trng in t trong di tn t 0 Hz n 300 GHz nh sau:Bng 11. Bng quy nh gii hn trng in, trng t v trng in t ca khuyn ngh s 1999/519/EC i vi khu vc cng cngDi tn

Mt thng lng t (mT)

Mt dng in(mA/m2)(rms)

Mc SAR trung bnh trn ton b c th(W/kg)SAR cc b (u v thn ngi)(W/kg)

SAR cc b (chn tay)(W/kg)

Mt cng sut S(W/m2)

0 Hz40-----

> 0-1 Hz-8----

1-4 Hz-8/f----

4-1000 Hz-2----

1000 Hz-100 kHz-f/500----

100 kHz-10MHz-f/5000,0824-

10 MHz-10GHz--0,0824-

10-300 GHz-----10

Ghi ch:1. l tn s tnh bng n v Hz.2. i vi cc tn s n 100kHz, cc gi tr mt dng in nh c th tnh bng cch nhn gi tr rms vi 2 (=1,414).3. Tt c cc gi tr SAR c tnh trung bnh trong khong thi gian 6 pht bt k.Cc mc tham chiu i vi cc trng in, trng t v trng in t trong di tn t 0 Hz n 300 GHz:Bng 12. Bng quy nh mc tham chiu i vi trng in, trng t v trng in t ca khuyn ngh s 1999/519/ECDi tnCng trng in E (V/m)Cng trng t H (A/m)B-field (T)Mt cng sut sng phng tng ng Seq(W/m2)

0-1 Hz-3,2 x 104x 104-

1-8 Hz10 0003,2 x 104/f24 x 104/f2-

8-25 Hz10 0004000/f5000/f-

0,025-0,8 kHz250/f4/f5/f-

0,8-3 kHz250/f56,25-

3-150 kHz8756,25-

0,15-1 MHz870,73/f0,92/f-

1-10 MHz87/f1/20,73/f0,92/f-

10-400 MHz280,0730,0922

400-2 000 MHz1,375f1/20,0037f1/20,0046f1/2f/200

2-300 GHz610,160,2010

Ghi ch:1. n v ca ly theo n v ghi ct Di tn.2. i vi cc tn s trong di tn t 100 kHz n 10 GHz, cc gi tr Seq, E2, H2, v B2 c ly trung bnh trong khong thi gian 6 pht bt k.3. i vi cc tn s trong di tn ln hn 10 GHz, cc gi tr Seq, E2, H2, v B2 c ly trung bnh trong khong thi gian 68/f1,05 pht bt k ( tnh bng GHz).Bng 13. Mc gii hn dng in tip xc ca khuyn ngh s 1999/519/ECDi tnDng in tip xc ti a (mA)

0 Hz - 2,5 kHz0,5

2,5 kHz - 100 kHz0,2 f

100 kHz - 110 MHz20

Mt s tiu chun khc ca chu u v phi nhim i vi ngi v SAR: CENELEC EN 50360 - Compliance to human exposure to EM fields (300 MHz - 3 GHz). CENELEC EN 50385 - Radio base and fixed terminal human exp. to EMF (110 MHz 40 GHz) CENELEC EN 50371 - Low power apparatus compliance to EM exposure (10 MHz 300 GHz) CENELEC EN 62311 - Assessment of electronic and electrical equipment human exposure to EMF (0Hz - 300GHz) CENELEC EN 62209 - Human exp. from hand-held and body-mounted wireless comm. devices CENELEC EN 50383 - Radio base and fixed terminal, EMF calc. and meas., SAR (110 MHz-40 GHz) CENELEC EN 50361 - SAR measurement, human exp. to EMF from mobile phones (300 MHz-3 GHz) IEEE 1528 - Determining SAR in the human head from wireless devices FCC OET 65C - Compl. of mobile and portable devices with FCC limits, human exp. to RF.3.5. CanadaCanada ban hnh lut an ton s 6 v gii hn mc phi nhim i vi con ngi trong trng in t tn s v tuyn in di tn s t 3 kHz n 300 GHz (Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz - Safety Code 6). Lut ny c ban hnh ln u vo nm 1991, ln 2 vo nm 1999 v phin bn hin ti c ban hnh nm 2009.Lut an ton s 6 -2009 (Safety Code 6):Lut ny c ban hnh nhm cc mc ch sau: Quy nh cc mc gii ti a nht v phi nhim ca con ngi i vi nng lng tn s v tuyn in trong di tn s t 3 kHz n 300 GHz nhm ngn nga tc hi n sc kho con ngi. Quy nh gii hn ti a v dng in cm ng v dng in tip xc nhm ngn nga tc ng vt l ca dng in gy ra bi nng lng tn s v tuyn trong cc mi trng khng c kim sot v ngn chn hin tng con ngi b bng hoc b in git trong mi trng c kim sot. Cung cp hng dn nh gi mc phi nhim tn s v tuyn m bo rng con ngi trong cc mi trng c kim sot v khng c kim sot khng b phi nhim mc cao hn mc gii hn cho php quy nh trong Lut.Quy nh v mc phi nhim ti a cho php:Trong di tn s t 100 kHz n 300 GHz, s lm nng m th s nh hng n sc kho l ni tri nht cn c phng trnh. Cc nh hng khng phi v nhit xy ra ti ngng nh hng nhit th cha c bng chng thuyt phc. Cc nghin cu trn ng vt cho thy ngng nh hng n s thay i hnh vi v thay i nhit thn ngi khong ~1.00C ti mc SAR khong ~4 W/kg. y l c s khoa hc ca mc gii hn SAR trung bnh trn ton b c th ngi ca Lut an ton s 6. m bo nh hng nhit c ngn chn, trong mi trng c kim sot h s an ton phi nhim l 10 do gii hn SAR trung bnh trn ton b c th ngi l 0.4 W/kg. i vi mi trng khng c kim sot, bo v ngi dn, h s an ton phi nhim l 50 do gii hn SAR trung bnh trn ton b c th ngi l 0.08 W/kg.Bng 14. Bng gii hn mc SAR trung bnh trn c th ngi ca SC6B phnGii hn SAR (W/kg)

Mi trng c kim sotMi trng khng c kim sot

Mc SAR trung bnh trn ton b c th ngi0.40.08

Mc SAR nh i vi u, c, thn ngi tnh trung bnh trn 1g m81.6

Mc SAR nh chn, tay tnh trung bnh trn 10g m204

Quy nh v gii hn dng in tip xc v dng in cm ng i vi mi trng c kim sot:Bng 15. Bng gii hn dng in tip xc v dng in cm ng i vi mi trng c kim sot ca SC6Tn sRms dng in cm ng (mA) quaRms dng in tip xc (mA) tay v qua tng chnThi gian trung bnh

C 2 chnTng chn

0,003 - 0,12000f1000f1000f1s

0,1 - 1102001001006 pht

Ghi ch: tn s f tnh bng n v MHz.Quy nh v gii hn dng in tip xc v dng in cm ng i vi mi trng khng c kim sot:Bng 16. Bng gii hn dng in tip xc v dng in cm ng i vi mi trng khng c kim sot ca SC6Tn sRms dng in cm ng (mA) quaRms dng in tip xc (mA) tay v qua tng chnThi gian trung bnh

C 2 chnTng chn

0,003 - 0,1900f450f450f1s

0,1 - 1109045456 pht

Ghi ch: tn s f tnh bng n v MHz.Gii hn v dng in tip xc v dng in cm ng trung bnh theo thi gian i vi thi gian o nhim khc nhau trong di tn t 0.1 n 110MHz:Bng 17. Bng gii hn v dng in tip xc v dng in cm ng trung bnh theo thi gian i vi thi gian o nhim khc nhau ca SC6Thi gian o phi nhim (pht)Dng in cm ng trung bnh theo thi gian (Rms) qua tng chn (mA)

Mi trng c kim sotMi trng khng c kim sot

610045

511049

412355

314164

217378

1245110

0,5346155

< 0,5350155

Quy nh gii hn v cng trng in v cng trng t:Trong vng trng xa, cng trng in, cng trng t v mt cng sut c lin quan vi nhau bng biu thc ton hc, theo khi xc nh c mt tham s bt k trong cc tham s ny th s xc nh c 2 tham s cn li. Trong vng trng gn, cn phi thc hin o c cng trng in v cng trng t v khng c mi quan h n gin no gia 2 i lng ny. Thc t th cc thit b o kim cc trng t ti mt s tn s c th khng c sn, trong trng hp th vic o kim trng cng in cn c thc hin nh gi s ph hp vi cc gii hn c bn trong lut ny.Vic nh gi trung bnh theo khng gian c thc hin trn mt din tch tng dng vi tit din dc ca c th ngi. Thi gian o kim trung bnh l 6 pht p dng i vi cc tn s n 15GHz, i vi cc tn s ln hn th thi gian o trung bnh s l 616 000/ f1/2, trong f l tn s tnh bng MHz.

Bng 18. Cc gii hn phi nhim i vi mi trng c kim sot

Bng 19. Cc gii hn phi nhim i vi mi trng khng kim sot

* Mt cng sut p dng i vi cc tn s ln hn 100MHz.Ghi ch:+ Tn s c tnh bng n v MHz.+ Mt cng sut 10W/m2 tng ng vi 1mW/cm2.Biu mc gii hn phi nhim:+ Trng in:

Hnh 6. Biu mc gii hn phi nhim trng in+ Trng t:

Hnh 7. Biu mc gii hn phi nhim trng t

Biu mc gii hn dng in cm ng v dng in tip xc:+ Mi trng c kim sot:

Hnh 8. Biu gii hn dng in cm ng v dng in tip xc trong mi trng c kim sot

+ Mi trng khng c kim sot:

Hnh 9. Biu gii hn dng in cm ng v dng in tip xc trong mi trng khng c kim sotTrn c s Lut an ton s 6, Canada ban hnh cc vn bn hng dn sau: Health Canada. BPR-1 Issue 5 (01/2009) - Broadcasting Procedures and Rules - Part I: General Rules (Cc quy nh v cc th tc kim sot v i pht qung b - Phn 1: Nhng quy nh chung). Industry Canada. GL-01 (10/2005) - Guidelines for the Measurement of Radio Frequency Fields at Frequencies from 3 kHz to 300 GHz (hng dn o kim cc trng tn s v tuyn in di tn t 3 kHz n 300 GHz). Industry Canada. GL-02 (10/2005) - Guidelines for the Protection of the General Public in Compliance with Safety Code 6 (hng dn bo v khu vc cng cng theo Lut an ton s 6). Industry Canada. GL-08, Guidelines for the Preparation of Radio Frequency (RF) Exposure Compliance Reports for Radiocommunication and Broadcasting Antenna Systems - Hng dn lp bo co nh gi s tun th phi nhim tn s v tuyn in i vi h thng anten thng tin v tuyn v qung b. TN-261 (2/2011) - Safety Code 6 (SC6) Radio Frequency Exposure Compliance Evaluation Template (Uncontrolled Environment Exposure Limits) - Th tc n gin nh gi s ph hp Lut an ton s 6 i vi phi nhim tn s v tuyn in (gii hn phi nhim mi trng khng c kim sot). TN-329 (2/2011) - Safety Code 6 (SC6) Measurement Procedures (Uncontrolled Environment) - Th tc o kim an ton theo Lut an ton s 6 (Mi trng khng c kim sot).3.6. cc ban hnh cc tiu chun v an ton bc x tn s v tuyn in bao gm: AS/NZS 2772-1: 1998, Radiofrequency radiation - Part 1: Maximum exposure levels 3kHz to 300GHz (Bc x tn s radio - Phn 1: Mc phi nhim ln nht trong di tn t 3kHz n 300GHz). AS/NZS 2772.2:2011 Radiofrequency fields Part 2: Principles and methods of measurement and computation 3 kHz to 300 GHz (Bc x tn s radio - Phn 2: Nguyn l v phng php o trong di tn t 300kHz n 100GHz). AS/NZS 4346, Guide to the installation in vehicles of mobile communication equipment intended for connection to a cellular mobile telecommunication service (CMTS) (Hng dn lp t phng tin truyn ca thit b truyn thng di ng dng ni n dch v vin thng di ng).

3.7. Vit NamHin ti Vit Nam, cng tc tiu chun ha lin quan n cng tc qun l an ton bc x tn s v tuyn in gm cc tiu chun v quy chun sau: TCVN 3718-1: 2005: Qun l an ton trong trng bc x tn s radio - Phn 1: Mc phi nhim ln nht trong di tn s t 3 kHz n 300 GHz. TCVN 3718-2: 2007: Qun l an ton trong trng bc x tn s radio - Phn 2: Phng php khuyn co o trng in t tn s rai lin quan n phi nhim ca con ngi di tn t 100 kHz n 300 GHz. QCVN 8:2010/BTTTT: Quy chun k thut quc gia v phi nhim trng in t ca cc trm gc in thoi di ng mt t cng cng do B Thng tin v Truyn thng ban hnh. Quy chun ny bao gm quy nh v mc phi nhim ln nht cho php (tham chiu theo TCVN 3718-1: 2005) v phng php o kim, nh gi phi nhim ca cc trm gc in thoi cng cng. Tuy nhin Quy chun ny ch p dng cho vic o kim phi nhim ca cc trm gc BTS, khng p dng cho vic o kim phi nhim ca cc i v tuyn in khc, trong cc i pht thanh v truyn hnh.3.7.1. Gii thiu tm tt v TCVN 3718-1: 2005Cu trc ca Tiu chun TCVN 3718-1: 2005 bao gm cc phn sau: Phm vi p dng i tng p dng Ti liu vin dn nh ngha v n v Gii hn phi nhim do ngh nghip Gii hn phi nhim khng do ngh nghip Kim tra s ph hp vi tiu chun Bo v - phi nhim do ngh nghip Bo v - phi nhim khng do ngh nghip Ph lc A (tham kho): C s xy dng mc phi nhim ln nht i vi bc x RF Ph lc B (tham kho): nh hng ca bc x RF Ph lc C (tham kho): Cc nguy him in hnh Ph lc D (tham kho): Gim nguy him RF h thng lp t mi Ph lc E (tham kho): Qun l nguy him RF3.7.1.1. Phm viTiu chun ny quy nh cc gii hn v mc hp th ring (SAR) v cc mc trng dn xut i vi vic phi nhim mt phn hoc ton b c th con ngi trong trng tn s radio (RF) di tn t 3kHz n 300GHz.3.7.1.2. i tng p dngTiu chun ny p dng nhng ni con ngi c th b phi nhim trong trng tn s radio khi lm vic v nhng ni cng chng co th b phi nhim.Tiu chun ny p dng cho trng sng lin tc (CW), trng xung v trng iu bin.3.7.1.3. Gii hn phi nhim do ngh nghipGii hn phi nhim i vi con ngi c xy dng trn c s c mt ngng phi nhim RF c SAR trung bnh trn ton c th l 4W/kg trc khi c kh nng xut hin cc nh hng gy bt li ti sc khe. Gii hn phi nhim do ngh nghip da trn c s gim phi nhim xung cn 1/10 mc ny (ngha l 0,4W/kg).Gii hn phi nhim do ngh nghip phi l:a) SAR trung bnh trn ton c th l 0,4W/kg, i vi phi nhim ng nht; hocb) SAR trung bnh trn ton c th ln n 0,4W/kg, i vi phi nhim khng ng nht, nhng vi gi tr SAR nh theo khng gian khng vt qu 8W/kg c ly trung bnh trn 1g m (coi th tch m dng hnh khi) ngoi tr bn tay, c tay, bn chn v mt c chn l ni m cc gi tr SAR nh theo khng gian khng c vt qu 20W/kg ly trung bnh trn 10g m dng hnh khi.Cc gi tri SAR phi c ly trung bnh trong thi gian 6 pht bt k ca ngy lm vic. Cc gi tr ny phi p dng cho s phi nhim ti cc tn s t 3kHz n 300GHz v phi c chng t bng tnh ton hoc k thut o thch hp.Tuy nhin, ti cc tn s thp hn 1MHz, nhng hiu ng do dng in chy qua c th s chim u th. Gii hn dng in tip xc v dng in cm ng qua c th ngi phi l cc gi tr nu trong bng 20B. Trong moi trng hp, phi tha mn c gii hn SAR ln dng in qua c th ngi.Bng 20. Mc phi nhim RF do ngh nghip v gii hn dng in RFBng 20A Mc phi nhim do ngh nghip dn xut theo trng in v trng t bin i theo thi gian (gi tr hiu dng khng b thay i)Di tn (MHz)Cng trng in E (V/m)Cng trng t H (A/m)Mt dng nng lng S (W/m2)Thi gian trung bnh cho cc php o |E|2, |H|2 hoc S (pht)

0,003 n 0,06561424,6(+)6

0,065 n 16141,6/f(+)6

1 n 10614/f1,6/f(+)6

10 n 400610,16106

400 n 300.000610,16106

Ghi ch: (+) Trong di tn s ny, vic o cng trng theo n v ny l khng ph hp; f l tn s tnh bng MHz.

Bng 20B Dng in cm ng v dng in tip xc RF*Di tn (MHz)Dng in cm ng, mADng in tip xc, mA

Qua c 2 chnQua tng chn

0,003 n 0,12000f1000f1000f

0,1 n 100200100-

0,1 n 30--100**

Ghi ch: * Gii hn dng in ny c th khng bo v chng cc phn ng v bng t ngt gy ra do phng in qu khi tip xc vi vt mang in** Mc d cc tiu chun khc a ra cc dng in tip xc RF ln nht i vi cc tn s ln hn 30MHz nhng hin nay khng th thc hin c cc php o cao hn tn s ny.Cc php o dng in cm ng qua c th ngi c ly trung bnh trong 6 min bt k v dng in tip xc c ly trung bnh trong 1s bt k; f l tn s tnh bng MHz

i vi phi nhim trong trng RF di dng xung trong di tn t 3kHz n 300GHz, cng trng in E hiu dng khng c vt qu 1950V/m trong giai on bt k. Dng in cm ng qua c th ngi khng c vt qu 500mA. Cng c th p dng cc mc nu trong bng 1.3.7.1.4. Gii hn phi nhim khng do ngh nghipTrong khi gii hn phi nhim do ngh nghip da trn vic gim phi nhim xung cn 1/10 mc ngng 4W/kg ngha l 0,4W/kg th gi tr phi nhim khng do ngh nghip c ly t 1/5 (hoc nh hn) mc gii hn phi nhim do ngh nghip. Do , gii hn phi nhim khng do ngh nghip c SAR trung bnh trn ton b c th ngi l 0.08W/kg.Gii hn phi nhim khng do ngh nghip phi l:a) Gi tr SAR trung bnh trn ton c th l 0,08W/kg, i vi phi nhim ng nht; hocb) Gi tr SAR trung bnh trn ton c th ln n 0,08W/kg i vi phi nhim khng ng nht, nhng vi gi tr SAR dnh theo khng gian khng vt qu 1,6W/kg c ly trung bnh trn 1g m (coi th tch m dng hnh khi) ngoi tr bn tay, c tay, bn chn v mt c chn l ni m cc gi tr SAR nh theo khng gian khng c vt qu 4W/kg ly trung bnh trn 10g m dng hnh khi.Cc gi tr SAR phi c ly trung bnh trong 6 min bt k ca mt ngy 24h. Cc gi tr ny phi p dng cho phi nhim ti cc tn s t 3kHz n 300GHz v phi c chng t bng tnh ton hoc k thut o thch hp.Ti cc mc phi nhim cho php trong bng 2, nguy him v in th gia con ngi vi t v dng in tip xc l khng ng k.

Bng 21. Mc phi nhim khng do ngh nghip dn xut theo trng in v trng t bin i theo thi gian (gi tr hiu dng khng b thay i)Di tn (MHz)Cng trng in E (V/m)Cng trng t H (A/m)Mt dng nng lng S (W/m2)Thi gian trung bnh cho cc php o |E|2, |H|2 hoc S (pht)

0,003 n 0,1870,73(+)6

0,1 n 1870,23/f0,5(+)6

1 n 1087/f0,50,23/f0,5(+)6

10 n 40027,50,07326

400 n 300.00027,50,07326

Ghi ch: (+) Trong di tn s ny, vic o cng trng theo n v ny l khng ph hp; f l tn s tnh bng MHz. Ti cc mc phi nhim cho php trong bng 2, dng in cm ng thp n mc ri ro v sc hoc bng RF l khng ng k.

i vi phi nhim trong trng RF di dng xung trong di tn t 3kHz n 300GHz, cng trng in hiu dng khng c vt qu 1940V/m trong giai on bt k. Cng c th p dng cc mc nu trong bng 2.3.7.1.5. Kim tra chng t s ph hp vi tiu chunNu khng c quy nh trong cc vn bn php quy k thut th s ph hp vi cc yu cu v cc gii hn phi nhim phi c kim tra bng cc php o trc tip.Cc php o chng t s ph hp vi tiu chun ny phi do ngi c trnh thch hp hoc ngi c thm quyn thc hin. Sau khi o, v trong trng hp mc cng sut khng thay i, cc kt qu phi c hiu lc trong mt khong thi gian do c quan c thm quyn th nghim thit lp.Vic kim tra s ph hp vi cc gii hn phi nhim phi c xc nh cho cc h thng lp t da trn mc cng sut v mc bc x cao nht pht ra trong cc iu kin lm vic bnh thng (khng tnh n cc iu kin s c) v phi xc nh li sau khi c bt k s thay i no c th lm tng mc cng sut bc x.Khi xut hin iu kin lm vic khng bnh thng hoc iu kin s c n mc c kh nng khng duy tr c s ph hp vi tiu chun th ngi vn hnh phi hnh ng ngay khi c th khi phc iu kin lm vic bnh thng v m bo s ph hp vi tiu chun.Cc php o mc phi nhim do ngh nghip phi l cc php o v tr bnh thng c ngi v hu ht cc v tr phi nhim c th c ngi. Khi php o cho thy mc trng bin i theo tng ngy v c th vt qu cc mc phi nhim do ngh nghip th phi c cc thit b th nghim v phi o mc phi nhim tng v tr m ngi lao ng c th b phi nhim do ngh nghip khng nh l mc ny thp hn cc mc nu trong bng 1A v 1B.Php o cc mc phi nhim khng do ngh nghip phi c thc hin ti im c mc phi nhim ln nht m ti bt c ngi no cng c th b phi nhim. Php o trng xaTrong trng xa ca anten, mt dng nng lng RF (S), cng trng in (E) v cng trng t (H) lin quan vi nhau bi cc biu thc sau:S = E*HE = (S*Z)1/2 = (S * 377)1/2, tc l E2 = 377*SH = (S/Z)1/2 = (S/377)1/2, tc l H2 = S/377E = Z*Htrong :E = cng trng in, tnh bng vn trn mtH = cng trng t, tnh bng Ampe trn mtS = mt dng nng lng in t, tnh bng ot trn mt vungZ = tr khng c tnh ca khng gian t do, tnh bng m 377Cc mi quan h cho thy, trong trng xa ca anten, mc phi nhim ln nht khng b vt qu nu mt trong cc gi tr mt dng nng lng RF (S), cng trng in (E) hoc cng trng t (H) nh hn cc mc tng ng nu trong cc iu 5 v 6 trong tiu chun ny, ngoi ra, khi cc php o trng xa c thc hin tn s nh hn 1MHz th cn thc hin php o trng in (E) ch ra s ph hp.Ch thch: i vi anten c cc kch thc thng ln nht l D mt lm vic tn s c bc sng m th khong cch tnh t anten trong iu kin trng xa l ln hn 2D2/ m v 0,5 m. Php o trng gnTrong trng gn phn x ca anten, khng p dng mi quan h gia S, E v H nu trn. Do phi o c cng trng in v cng trng t.Cn ch khi thc hin cc php o trong trng gn bc x gip ranh vi trng phn x.C nhiu thit b dng o mt dng nng lng RF, thc t l o gi tr bnh phng ca cng trng in hoc cng trng t, nhng c mt ng h o c hiu chun ch th mt dng nng lng. Khu vc trng gn, bao gm c trng gn phn x v trng gn bc x, ti cc khong cch tnh t ngun, bt u ti /2 m v 2D2/ m (hoc 0,5 m, chn gi tr nh hn).S lng ly mu phi c coi l nh hn mc phi nhim cc i nu thit b o ghi c gi tr nh hn mc tng ng ca mt dng nng lng RF i vi sng phng. C th s dng cc biu thc cho trong php o trng xa xc nh mc tng ng. Mt s thit b hin c c kh nng o c trng H ti cc tn s trn 300MHz.

Th nghim in hnh/nh gi v tr RFC th s dng th nghim in hnh cc ngun RF hoc nh gi v tr RF chng t s ph hp vi iu kin l c t nht hai ngun hoc hai v tr th nghim tng t c o v cc mc lin quan cho thy l c th so snh c trong phm vi khng m bo o thng thng l 3dB.Khng c s dng th nghim in hnh hoc nh gi v tr RF khi cc mc RF khng th d on c hoc b nh hng bi cc iu kin cc b, v d:a) cc thit b gia nhit RF v cc thit b hn nha dng trong cng nghip khi cc mc RF thay i ph thuc vo ch hn hoc vt liu cn hn.b) kt cu anten trong trng hp dng bc x c lin quan mt thit vi iu kin mt phng t ti ch.3.7.1.6. Bo v - phi nhim do ngh nghipNguyn l bo v tt c nhng ngi b phi nhim trong trng RF do cng vic ca h cc mc vt qu cc mc phi nhim khng do ngh nghip, phi bao gm:a) chnh sch c vn bn ha th hin s cam kt ca tt c cc bn vi chng trnh bo v, ngi lao ng phi t lm quen vi tt c cc quy trnh lin quan;b) vic kim sot v loi tr cc nguy him ngay ti ngun pht sinh bng thit k v b tr k hoch ph hp, v tr lm vic thch hp;c) thng l k thut nh bc kim, kha lin ng an ton, b pht hin dng r lp sn v chung bo, ct bn di ng dn sng, v cc ro cn vt l;d) xc nh ranh gii mc trng phi nhim do ngh nghip ca cc ngun RF hin c. Trong cc khu vc ny phi p dng cc yu cu sau: ti thiu ha s phi nhim; kim sot hnh chnh bao gm hn ch thi gian phi nhim, tng khong cch gia ngun v ngi lao ng, hn ch tip cn v gim cng sut tm thi; duy tr cc mc phi nhim tt c cc khu vc ngi lao ng d tip cn sao cho mc phi nhim khng vt qu cc mc quy nh trong bng 1A v 1B; cung cp qun o bo v hoc thit b bo v c nhn, hoc c hai, bo v c hiu qu ti cc tn s quan tm v khng c in th gy h quang hoc nh la, gim mc phi nhim khi cn thit;e) c cc bin bo hoc cc du hiu, hoc c hai, nhn bit cc khu vc vt qu mc phi nhim do ngh nghip hoc cc khu vc bt buc phi mc qun o bo v hoc s dng thit b bo v;f) c cc bin bo hoc cc du hiu, hoc c hai, ch ra s c sn qun o v thit b bo v v cc yu cu bt buc ngi lao ng phi mc qun o bo v hoc s dng thit b bo v ny;g) nh k xem xt k cc nguyn l hoc cc quy trnh c chp nhn vi nhng thay i c chp nhn khi cn hiu hoc i ph vi nhng thay i trong mi trng hp.h) kho st y t cho ngi lao ng b phi nhim do ngh nghip m bo b tr an ton, thit lp tnh trng ranh gii v pht hin sm bt k du hiu thay i no. Trong mi trng hp, cc chng trnh c bit phi c chuyn gia c cng nhn trong lnh vc y t ngh nghip vch ra v gim st. Cc vn cn quan tm l vic nh gi cc thit b c cy kim loi v cc thit b y t khc nhy vi nhiu RF v nhng thay i c th c i vi mt ngi;i) lu gi cc h s v cc php o trng RF v h s theo di sc khe;j) thng bo ca c quan chc nng c thm quyn trong trng hp phi nhim qu mc hoc s c.Ngi lao ng mang thai khng c phi nhim cc mc vt qu gii hn phi nhim khng do ngh nghip. Khi cc vt th kim loi c ln c a vo trng RF th phi c cc bin php phng nga, c bit ti cc tn s thp hn 30MHz, trnh bng RF nghim trng hoc b git khi chm phi cc vt kim loi trong trng in t m thng thng khng c ni t, v d nh cc phng tin vn ti ko bng ng c in, kt cu xy dng, hng ro hoc dng c. S tch in trong cc vt nh vy c th gy nguy him cho con ngi hoc ti sn v cn phi cho phng in hoc gim mc ca trng xung. Ni chung, s khng xy ra bng RF nu dng RF do tip xc nh hn hoc bng 50mA.Phi xc nh cc khu vc c th xy ra cc hiu ng ny bng php o v phi ch r bng cc bo hiu nhn thy c.Khi ngi lao ng cn phi lm vic trong cc khu vc gn vi mc nu trong bng 1 th phi thc hin vic hun luyn thch hp v quy trnh an ton v cc nh hng n sc khe.3.7.1.7. Bo v - phi nhim khng do ngh nghipVi cc kin thc hin c th cc gii hn SAR v cc mc trng dn xut i vi phi nhim trong trng RF c cp trong tiu chun ny s cung cp mt mi trng sng v lm vic khe v an ton vi phi nhim trong trng RF trong cc iu kin bnh thng. Tuy nhin, s hiu bit v cc ngng i vi hiu ng sinh hc quan st c v cc nh hng sc khe tim n l cha y . Chnh v vy, cn thn trng xem xt trnh phi nhim khng cn thit t c mc ch, trong khi tnh n thc tin hin i v hiu qu chi ph ca bt k b tr c th no.Cc nguyn l bo v cng chng c th b phi nhim trong trng RF do gn anten hoc cc ngun RF khc phi bao gm:a) xc nh ranh gii ca cc khu vc p ng cc mc phi nhim khng do ngh nghip, cung cp cc bin bo ph hp v hn ch cng chng tip cn n cc khu vc ny.b) gim mc cng sut bc x sao cho mc phi nhim trong khu vc ni m khng th khng c cng chng xung mc ph hp vi cc mc phi nhim khng do ngh nghip ca tiu chun ny;c) quy hoch s dng t;d) chp nhn cc ng dng hin i nht v trnh phi nhim khng cn thit m vn t c mc ch dch v.3.7.2. Gii thiu v TCVN 3718-2: 2007Cu trc ca Tiu chun bao gm cc ni dung sau: Phm vi p dng Ti liu vin dn nh ngha Cc lu v php o lin quan n nh gi nguy him RF c tnh ca bc x trng in t tn s radio (EM RF) Tm tt cc vn gp phi trong cc php o Vn o SAR Lu i vi php o dng in cm ng Thit b o H thng o trng ngoi c tnh in mong mun c tnh vt l mong mun Thit b o trng ngoi Thit b o dng in cm ng (c th) Thit b o trng bn trong v SAR Php o trong trng phi nhim c nguy c tim n Quy trnh o i vi trng ngoi Php o dng in cm ng trong c th v dng in tip xc Quy trnh o trng bn trong (SAR) S dng d liu kim tra trng gn nh gi SAR tim n vt qu ngi b phi nhim3.8. Nhn xtQua nghin cu cho thy, cc nc nh M, Canada, Chu u, v Vit Nam u c quy nh v gii hn an ton phi nhim trng in t i vi con ngi v mc gii hn an ton l tng ng vi nhau. Tuy nhin trong di tn t 400 MHz tr ln yu cu trong TCVN ( 2W/m2) cao hn cc nc khc (mc gii hn nm trong di t 2 -10W/m2).

CHNG 4. NGHIN CU PHNG PHP O KIM, NH GI PHI NHIM TRNG IN T I VI CC I PHT THANH V TRUYN HNH CA MT S NC TRN TH GII4.1. Canada4.1.1. GL-01 (11/2005) - hng dn o kim cc trng tn s v tuyn in di tn t 3 kHz n 300 GHz4.1.1.1. Th tc o kim mc nng lng RF ti khu vc xung quanh i pht thanh FM/pht thanh s, i truyn hnh VHF, UHF v truyn hnh s v truyn hnh MDS.Phn ny hng dn o mc nng lng RF ca cc i pht thanh FM (88-108 MHz), pht thanh s (1452-1492 MHz), truyn hnh VHF, UHF, truyn hnh s 54-72 MHz, 76-88 MHz, 174-216 MHz, 470-806 MHz v truyn hnh MDS hot ng bng tn 2596-2686 MHz.Vic o kim trng phi do cc cn b c o to v c kin thc k thut v qung b thc hin.a) Xc nh vng o: Xc nh cc khong cch o thch hpTrc tin phi tnh ton trn l thuyt xc nh bn knh ti a thc hin php o trn c s phn tch phn b mt cng sut ca mi i pht sng. Vic phn tch ny cn c xem xt mt cng sut cho php ti mi tn s theo phng ng v phng ngang ca tng anten theo cu trc anten, biu phng v v gc ngng ca tng anten, kiu iu ch, phn cc ca anten bc x, cao mt t ca khu vc gn anten v mc ERP ti a ca mi i pht sng.Phn mm d on mt cng sut, v d nh 'HIFIELD', c th s dng c lng v tr ti hn (vng tun th) m bn trong mc phi nhim c th vt qu gii hn cho php ca Lut an ton s 6. Hu ht cc phn mm loi ny u c tch hp sn vic tnh ton gii hn an ton v khong cch o kim ti a (vng lin quan). Khi xem xt biu bc x tnh ton v c lng khong cch ti a cn phi o kim, th cng cn c dung sai do cu trc m anten h tr. Xc nh cc v tr oVic xc nh cc v tr o tu thuc vo h thng ang xem xt. Vic o kim nn c thc hin dc theo ti thiu 8 vng trn ng tm tnh t trung tm im tham chiu (v d nh chn thp anten) n khong cch o kim ti a nh xc nh trn. Nu vic o kim c thc hin ti tng im ring l thay cho vic o kim lin tc th khong cch ti a gia cc im o khng c vt qu 2m.S lng cc vng trn c th tng v/hoc khong cch o kim ti a tnh t trung tm im tham chiu c th m rng nu kt qua o c cho thy cn phi thc hin o thm nhm m bo tt c cc v tr ti hoc gn i pht ni dn chng c th thm nhp c tun th gii hn an ton theo Lut an ton s 6.b) Thc hin o: Phng php oi vi cc khu vc ch c i pht n, vic o kim c th c bng cc thit b bng rng hoc thit b o chn tn tng ng.i vi cc khu vc c nhiu i pht th s dng thit b o bng rng o c mt cng sut tng cng l thch hp hn. C th s dng thm my phn tch ph d ton b ngun pht x ti khu vc o v: Nu khng c ngun pht sng c tn s di 30MHz v trn 300MHz th vic o kim c th thc hin bng thit b c p ng tn s - bin phng. Nu c ngun pht sng c tn s di 30MHz v trn 300MHz th thit b phi l thit b p ng trng s th hin c ng gii hn theo Lut an ton s 6.Ti tng im o, ngi kho st cn phi tun th cc th tc c nu trong Hng dn. Thng thng, vic ny c thc hin bng cch gi u d cch xa ngi v trong phm vi cch ngi o vi mt khng c vt no. Ngi o khng ng trn ng thng ni t ngun pht n u d (khng trc v khng sau). minh ho r hn, gi s ngi o quay mt v pha ngun pht th tay cn dang rng ra xa gi u d v u d cha thng v pha ngun pht sng.Trong trng hp s dng gi 3 chn, th gi 3 chn khng c lm bng kim loi trnh hiu ng nh thng. S cng hng ca cc thit b c th gn cc tn s lin quan v cc nhiu k sinh ny c th gy ra nhiu ng k.Nu i truyn hnh analog c kim v c trm pht sng hot spot m mt cng sut vt qu 75% gi tr mt cng sut cho php th phi ghi chp c gi tr o trung bnh v gi tr nh c o trong khong thi gian 1 pht.Vic o kim t m hn cn phi c thc hin ti khu vc c cc vt th tin tng gy phn x, v d nh tng, hng ro, mc d cc v tr ny khng nm trn cc ng trn c la chn. Vic o kim ti v tr cch cc vt th mt khong t hn 20 cm khng c gi tr. Bo co kt qu oBo co kt qu o kim phi c cc d liu sau: M t chung v khu vc v h thng pht sng. nh gi ph hp hay khng ph hp so vi cc gii hn an ton ca Lut an ton s 6. nh du tt c cc gi tr o c m vt 50% gi tr p dng v v tr ca cc im (hoc khu vc) ny; v Cung cp cc m t v phng tin cn thit p dng ti cc v tr v cc im truy nhp (hot spot) vt qu cc mc gii hn an ton tng ng ngn nga hoc cnh bo ngi dn xm nhp.4.1.1.2. Th tc o kim mc nng lng RF ti khu vc xung quanh i pht thanh AMPhn ny m t vic o kim i pht thanh AM ti bng tn 525 n 1705 kHz. Vic o kim trng phi do cc cn b c o to v c kin thc k thut v qung b thc hin. Th tc ny cng c th p d i vi i pht thanh AM cng sut thp.a) Xc nh vng o: Tnh ton khong cchTrc tin phi tnh ton trn l thuyt xc nh bn knh ti a thc hin php o trn c s phn tch phn b mt cng sut ca mi i pht sng. Vic phn tch ny cn c xem xt mt cng sut cho php ti mi tn s theo phng ng v phng ngang ca tng anten theo cu trc anten, biu phng v v gc ngng ca tng anten, kiu iu ch, phn cc ca anten bc x, cao mt t ca khu vc gn anten v mc ERP ti a ca mi i pht sng.Do c cc khong cch gia cc thit b pht sng (thp pht sng) trong dy i pht AM, mi thp pht sng phi c nh gi ring r. Do , i vi mi thp pht sng, mi vng o kim c th c thit lp bng cch s dng bng di y. Bng 22. Bng quy nh khong cch an ton i vi i AM theo GL-01

Cc gi tr trong bng c tnh ton bng phn mm NEC (Numeric Electromagnetic Code) p dng i vi cc b bc x thng. M hnh ny gi s khong cch trong trng hp xu nht (worst-case) tnh t thp anten AM n. Cc khong cch xen gia c th c lng ni suy t 2 gi tr khong cch gn nht. Nu s dng phng php bng trn, vung o kim ca mi thp cn c xc nh bng cng sut vo tng ng. Cn nu ch s dng phng php xp x (approximate method) th thng phng php ny chnh xc cho hu ht cc trng hp. Trong trng hp c nghi ng, i vi cc thp cng sut thp th bn knh o kim ti thiu c xut l 5m. Xc nh cc v tr oGii hn an ton theo Lut an ton s 6 s c xc nh nm dc trn vng gn trn hoc gn ging hnh qu trng xung quanh chn thp anten. Khi o kim chi tit, t nht phi thc hin o ti 4 im trn tng vng trn ca tng thp anten bt u t vng trn c bn knh ln nht chuyn dch vo trong pha chn thp. Tuy nhin, thng thng th ch cn xem xt thp nng nht. Bn knh o kim tnh ton trn l thuyt c th phi tng ln nu kt qu o ti im o u tin vt qu mc gi tr cho php ca Lut an ton s 6 i vi khu vc cng cng.b) Thc hin o: o trng in H, trng t H v mt cng sutThng thng vng o kim ca i pht AM nm trong vng trng gn v trng phn ng ca anten (near and reactive field) do cn phi thc hin o c trng E v trng H. i vi i pht n, c th s dng thit b o bng rng hoc thit b o chn tn thc hin o kim.i vi khu vc c nhiu i pht th cn phi thc hin nh sau: i vi khu vc c 2 i pht AM: do gii hn ca Lut an ton s 6 ph thuc vo tn s trong di tn khong 1MHz, do cch n gin nht xc nh khong cch l s dng gi tr cng sut tng ng vi tng cng sut ca 2 i pht v tn s ln nht xc nh gii hn cho php theo Lut an ton s 6. Mt khc, cn phi xc nh v cng gi tr (bnh phng ca tng cng trng) ca tng ngun xc nh s ph hp, th tc ny yu cu phi ln lt tt tng i pht trong qu trnh o kim. i vi khu vc c i pht c AM v FM: s khc nhau v trng s ca tng ngun l ng k v xc nh t l phn trm ca tng ngun th cn phi tt ln lt tng ngun thc hin o. Phn ng gp ca cc i pht VHF ti khu vc ang kho st c xc nh bng cch dng my o mt cng sut c p ng trng s th hin c ng ng gii hn theo Lut an ton s 6. Tng cng cc phn ng gp ca i pht AM v FM cn c xc nh thit lp vng vt qu mc gii hn ca Lut an ton s 6.Ti tng im o, ngi kho st cn phi tun th cc th tc c nu trong Hng dn. Thng thng, vic ny c thc hin bng cch gi u d cch xa ngi v trong phm vi cch ngi o vi mt khng c vt no. Ngi o khng ng trn ng thng ni t ngun pht n u d (khng trc v khng sau). minh ho r hn, gi s ngi o quay mt v pha ngun pht th tay cn dang rng ra xa gi u d v u d cha thng v pha ngun pht sng.Trong trng hp s dng gi 3 chn, th gi 3 chn khng c lm bng kim loi trnh hiu ng nh thng. Hiu ng nhiu trng ti trng cc b c th lm mt hiu lc ca php o.Vic o kim t m hn cn phi c thc hin ti khu vc c cc vt th tin tng gy phn x, v d nh tng, hng ro, mc d cc v tr ny khng nm trn cc ng trn c la chn. Vic o kim ti v tr cch cc vt th mt khong t hn 20 cm khng c gi tr. o dng in cm ngVic o dng in cm ng nn c thc hin ti cc khong cch tnh ton theo gii hn ca Lut an ton s 6. Ti mi khong cch ny cn thc hin t nht l 4 ln o. Cc v tr o c la chn trong vng o phi l cc v tr c mc nng lng RF cao nht c ghi chp li. Vic o kim thc t c thc hin bng cch s dng ng h o dng in cm ng vi anten bng rng m phng ging nh ngi (cao khong 1,75m). Nu khng c anten m phng ngi m dng vt th khc thay th th phi m bo mt trc/sau ca vt th phi thng hng vi thp anten. o dng in tip xcVic o dng in tip xc c th yu cu cc cng trnh dn in gn (nh vt th, to nh, hng ro v dy dn,). Cc cng trnh ny phi c nh gi ring cho tng trng hp. Khong cch trong vng o s l mt hm ca kch thc v phng hng ca cng trnh, khong cch t cng trnh n anten v cng sut ca i pht.Vic o kim c thc hin bng cch dng ng h o dng in tip xc c a hoc kp tip t thch hp. Vn quan trng l phi m bo u d hoc thit b u ni phi tip xc tt vi i tng cn o.

Bo co kt qu oBo co kt qu o kim phi c cc d liu sau: M t chung v khu vc v h thng pht sng. nh gi ph hp hay khng ph hp so vi cc gii hn an ton ca Lut an ton s 6. nh du tt c cc gi tr o c m vt 50% gi tr p dng v v tr ca cc im (hoc khu vc) ny; v Cung cp cc m t v phng tin cn thit p dng ti cc v tr v cc im truy nhp (hot spot) vt qu cc mc gii hn an ton tng ng ngn nga hoc cnh bo ngi dn xm nhp. Ch r nhng v tr c th trong vng ny m gn vi vt bng kim loi v cc vt th phn x tim nng.4.1.2. TN-329 (2/2011) - Th tc o kim an ton theo Lut an ton s 6 (Mi trng khng c kim sot)Mc ch ca ti liu k thut ny l m t th tc o kim i vi cc loi cng trnh qung b, thng tin v tuyn khc nhau xc nh s ph hp i vi gii hn an ton ca khu vc khng c kim sot theo Lut an ton s 6.Qu trnh nh gi:Cc bc xc nh s ph hp vi Lut an ton s 6 theo cc gii hn i vi mi trng khng c kim sot ti mt khu vc c th ca h thng anten qung b hoc thng tin v tuyn nh sau: (1). Trc khi thc hin o kim ti hin trng th cn phi thc hin vic kho st hin trng. Tt c cc d liu phi c thu thp bao gm: cc i qung b trong bn knh 1km, cc trm pht c nh mt t ca h thng di ng, t bo, PCS, vi ba, rada v dch v nh v v tuyn trong phm vi bn knh 100m tnh t khu vc xem xt.(2). Thc hin tnh ton (theo TN-261 v/hoc phm mm HIFIELD) c lng mc RF trong trng xa i vi khu vc xem xt xc nh cc v tr tng i cn phi o kim (v d nh cc v tr m tnh ton cho thy mc RF ln hn hoc bng 50% mc gii hn ca mi trng khng c kim sot).Ghi ch: nu theo phn tch l thuyt cho thy khng c v tr no bng hoc vt qu 50% mc gii hn cho php ca mi trng khng c kim sot (trong khu vc ngi dn c th tip cn) th khu vc xem xt c coi l ph hp v khng cn phi thc hin o kim.(3). Khong cch trng xa phi c xem xt khi la chn cc v tr o. Thng thng nu mt v tr trong vng trng xa ca tt c cc thnh phn bc x th ch cn o trng E l . Nu khng th cn phi o c trng E v trng H.(4). Tu theo kt qu kho st hin trng la chn thit b o bng rng v/hoc bng hp thc hin o ti hin trng.(5). Ly cc v tr c xc nh trong mc (2) lm im bt u, thc hin i b vng quanh khu vc xem xt theo phng php quy nh ca GL-01 xc nh cc v tr c mc RF cao ( 50% gi tr gii hn ca mi trng khng c kim sot, bao gm c iu kin khng m bo o).(6). Vic o kim ti hin trng nn c thc hin vi iu kin lun nhn thy anten. Trong trng hp o trn nc nh, vic o kim phi c thc hin t nht l ti tt c cc v tr m ngi dn c th b phi nhim ti hng bp sng chnh ca cc anten.(7). Kt qu o kim phi gm d liu v v tr o, thng s c trn my o v thi gian o.(8). Cc iu kin khng m bo o phi c xem xt trong qu trnh kho st.4.1.3. TN-261 (2/2011) - Th tc nh gi s ph hp Lut an ton s 6 i vi phi nhim tn s v tuyn in (gii hn phi nhim mi trng khng c kim sot)Ti liu ny ban hnh nhm mc ch cung cp cng c nh gi nhanh s ph hp vi gii hn cho php ca Canada v phi nhim trng in t ca cc i v tuyn n gin. Phng php nu trong ti liu ny ch hp l i vi cc vng nm trong trng xa ca anten v khng phn tch chi tit v s ph hp. Trng hp nh gi chi tit th cn phi c k thut phn tch da trn s liu thc t v c s dng biu bc x thc ca anten v c xem xt n c cc ngun bc x khc trong khu vc xem xt.Ti liu k thut ny phc tho mt th tc nh gi xc nh s ph hp v phi nhim trng in t vi Lut an ton s 6 (SC6).Qu trnh nh gi s ph hp vi SC6 gm 3 bc. Cc phng php nh gi nu trong bc 1 v bc 2 p dng nh gi c hu ht cc i pht n gin, cn i vi cc trng hp phc tp nh trn cc mi nh m ngi dn c th tip cn v c nhiu anten th cn phi c k thut phn tch chi tit hn bc 3.Bc 1: Chng thc hoc phn tchNu h s xin php c km theo mt chng thc hoc phn tch chp nhn c, th hin s ph hp vi yu cu ca SC6 i vi mi trng khng c kim sot th khng cn phi xem xt thm. Nu c nghi ng v s ph hp hoc h s khng c giy t chng thc hoc phn tch th thc hin tip bc 2.Bc 2: Phn tch vng khng c min o (non-Exemption Zone)S dng cc tham s k thut ca i pht v phng php nu trong ti liu ny thc hin nh gi. Nu i pht ph hp vi cc th tc nu trong mc 3.1 n 3.4 v 4 ca ti liu ny th khng cn phi nh gi thm. Tuy nhin nu i pht khng p ng cc th tc ca bc ny th thc hin tip bc 3.Bc 3: Phn tch ch tiu, o kim trng hoc o kim n gin Th tc nu trong mc 3.4 ca ti liu ny p dng i vi trng hp nhiu anten v nhiu bng tn l cch nh gi tng i qu mc i vi tn hiu RF. V s lng anten v bng tn tng th kt qu c lng tr nn thiu tnh thc t ti ra mc d on ln hn thc t o c, do cn phi c phng php khc thay th.Cn b th l h s c th m t mt s tu chn minh ho cho ngi np h s v s ph hp vi SC6. Ngi np h s c th la chn (i) cung cp cch tnh ton chi tit, (ii) thc hin o kim v/hoc (iii) thc hin php o n gin ti hin trng.(i) Phi thc hin tnh ton chi tit da trn tham s k thut thc t i vi tt c khu vc cng cng ngi dn c th tip cn c minh ho s ph hp SC6 i vi mi trng khng c kim sot. Vic ny gm cc tham s k thut chnh xc i vi mi anten pht nh gin hng tnh ng v ngang ca anten, tn s, cng sut bc x hiu dng (e.r.p), chiu cao ct anten v i vi trng hp c nhiu anten h tr nhiu cu trc th cn phi xc nh v tr theo phng ngang ca anten v im tham chiu tnh ton. Vic tnh ton c th thc hin bng cch s dng bng hoc phn mm m tnh tnh ton nh Hifield v c xem xt n vng trng gn v trng xa v cc gii hn ca SC6. Cn b nh gi phi xc thc vic tnh ton v trong trng hp tnh ton chi tit ch ra cc vng thm nhp c mc RF vt qu 50% gi tr gii hn ca mi trng khng kim sot hoc cn b nh gi khng chc chn l i pht ph hp vi SC6 th phi yu cu ngi np h s thc hin o kim hoc o kim n gin.(ii) Vic o kim chi tit phi c thc hin minh ho rng cc khu vc c th thm nhp c phi c gi tr trng tun th vi mc gii hn ca SC6 trong mi trng khng c kim sot. Ngi np h s phi cung cp bo co kt qu o chi tit (theo GL-08). Thng tin chi tit hn nu trong GL-01 v TN-329. Nu kt qu khng th hin s ph hp ngi np h s phi thc hin cc php o n gin. Cn b nh gi c th cc php o kim cn thc hin ti cc khu vc c th v v cc khu vc ngi dn thng tip cn. Cn b nh gi cng c th quan st vic thc hin o kim hoc s dng thit b o ca c quan thc hin php o.(iii) Ngi np h s c th ngh cc php o kim n gin nh gi s ph hp vi SC6. Vic ny c th bao gm (nhng khng gii hn) vic gim cng sut, thay i anten hoc c bin php ngn chn ngi dn thm nhp vo cc khu vc m c mc phi nhim ln hn mc gii hn quy nh ca SC6 i vi mi trng khng c kim sot. i vi cc php o kim n gin c khuyn ngh vi a s trng hp l p dng GL-02 (Hng dn bo v khu vc cng cng m bo s tun th theo SC6). Cn b nh gi c th yu cu o kim n gin nu vic xem xt cc ti liu do ngi np h s cung cp cha thy tho ng. Ngi np h s cn ngh C quan nh gi khi no th thc hin vic o kim n gin. Mc d s ph hp vi CPC-2-0-03 (Yu cu qun l i vi H thng anten bng b v thng tin v tuyn) v SC6 l iu kin tiu chun cp php, nhng cn b nh gi vn c th yu cu thm cc iu kin c th khc, v d ngi np h s phi minh ho s ph hp bng vic o kim hoc thc hin o n gin trc khi c cp giy php chnh thc. Ngoi ra cng c th c cc iu kin khc km theo giy php.Tng quan v phn tch vng khng c min o ng bin ca trng gn - trng xa c dng hnh cu l vng m khng c tip cn (nh hnh v di y).

Hnh 10. ng bin trng gn - trng xa ca anten

Cng thc xc nh bn knh ng bin vng trng gn - trng xa: Anten c kch thc nh so vi bc sng (D ): R = /2. Anten c kch thc ln so vi bc sng (D > ): R = 0,5D2/. V d anten pht sng tn s 875MHz (bc sng l 0,34m) chiu di mt bc x D = 1,22 bn knh ng bin l:R = 0,5*1,222/0,34 = 2,17m. Vng hn ch thm nhp (Restricted Zone) ca anten c xc nh theo cc tham s k thut ca anten l mt hnh tr bao quanh anten, trong mt trn ca hnh tr nm trong mt phng ngang ct qua tm an