C

CNG

QUY V P

A CC

from

HO X

QCVN

CHUNHI NH

C I PH

Nationalon electm Radio

HI CH

N 78:201

N K THHIM TRHT TH

l technictromagne

o and Tel

H NI

NGHA

14/BTTT

HUT QRNG HANH, T

cal regulaetic expolevision s

2014

A VIT N

TT

QUC GIN T

TRUYN

ation osure stations

AM

IA T N HNH

MC LC

1. QUY NH CHUNG ................................................................................................ 5 1.1. Phm vi iu chnh ........................................................................................... 5

1.2. i tng p dng ........................................................................................... 5

1.3. Ti liu vin dn ............................................................................................... 5

1.4. Gii thch t ng .............................................................................................. 5

1.5. K hiu v ch vit tt ...................................................................................... 8

2. QUY NH K THUT ........................................................................................... 9 2.1. Gii hn phi nhim khng do ngh nghip .................................................. 9

2.2. Quy nh v T l phi nhim tng cng TER ................................................ 9

3. PHNG PHP O .............................................................................................. 9 3.1. M t phng php ..................................................................................... 10

3.2. nh gi ton din T l phi nhim tng cng ........................................... 11

3.3. Phng php xc nh cc vng ................................................................. 12

3.4. Phng php o v xc nh gi tr T l phi nhim tng cng ................. 17

3.5. nh gi T l phi nhim tng cng .......................................................... 18

4. QUY NH V QUN L ..................................................................................... 18 5. TRCH NHIM CA T CHC, C NHN ........................................................ 18 6. T CHC THC HIN ........................................................................................ 19 PH LC A (Tham kho) Xc nh vng tun th ca i pht thanh FM, i pht thanh bng L v i truyn hnh VHF, UHF .................................................. 20 PH LC B (Tham kho) Xc nh ng bin ca vng lin quan ca i pht thanh FM, i pht thanh bng L v i truyn hnh VHF, UHF .......................... 23 TH MC TI LIU THAM KHO .......................................................................... 24

QCVN 78:2014/BTTTT

3

Li ni u QCVN 78:2014/BTTTT c xy dng trn c s TCVN 3718-1:2005 v cc ti liu hng dn Lut an ton s 6 ca Canada (Safety Code 6 - 2009 - Canada). QCVN 78:2014/BTTTT do Cc Vin thng bin son, V Khoa hc v Cng ngh thm nh v trnh duyt, B Thng tin v Truyn thng ban hnh km theo Thng t s 02/2014/TT-BTTTT ngy 10 thng 03 nm 2014.

QCVN 78:2014/BTTTT

4

QCVN 78:2014/BTTTT

5

QUY CHUN K THUT QUC GIA V PHI NHIM TRNG IN T

CA CC I PHT THANH, TRUYN HNH National technical regulation on electromagnetic exposure

from Radio and Television stations

1. QUY NH CHUNG

1.1. Phm vi iu chnh Quy chun ny quy nh mc gii hn phi nhim trng in t khng do ngh nghip v phng php o, nh gi s tun th i vi cc i pht thanh hot ng trn bng tn MF (i pht thanh AM), VHF (i pht thanh FM), L (i pht thanh s) v cc i truyn hnh hot ng trn bng tn VHF, UHF. 1.2. i tng p dng Quy chun ny p dng i vi cc c quan, t chc Vit Nam c hot ng pht tn hiu pht thanh, truyn hnh trn lnh th Vit Nam. 1.3. Ti liu vin dn [1] TCVN 3718-1:2005 Qun l an ton trong trng bc x tn s rai Phn 1: Mc phi nhim ln nht trong di tn t 3 kHz n 300 GHz. 1.4. Gii thch t ng 1.4.1. Anten (antenna) Anten l thit b thc hin vic chuyn i nng lng gia sng c dn hng (v d trong cp ng trc) v sng trong mi trng khng gian t do, hoc ngc li. Anten c th c s dng pht hoc thu tn hiu v tuyn. Trong Quy chun ny, nu khng c quy nh c th th thut ng anten c dng ch anten pht. 1.4.2. Cng sut bc x ng hng tng ng (Equivalent Isotropic Radiated Power - EIRP) Cng sut bc x ng hng tng ng c xc nh bi cng thc:

PEIRP = Pt - L + G (1) trong : - PEIRP (dBm): cng sut bc x ng hng tng ng; - Pt (dBm): tng cng sut ca cc my pht; - L(dB): tng suy hao t cc my pht n anten; - G(dBi): tng ch cc i ca anten tng ng vi anten ng hng. hoc:

PEIRP = Pt 10(G-L)/10 (2) trong : - PEIRP (W): cng sut bc x ng hng tng ng; - Pt (W): tng cng sut ca cc my pht; - L(dB): tng suy hao t cc my pht n anten;

QCVN 78:2014/BTTTT

6

- G(dBi): tng ch cc i ca anten tng ng vi anten ng hng. 1.4.3. Cng trng in (electric field strength - E) Cng trng in l ln ca vct trng ti mt im, xc nh bng lc F trn mt n v in tch q chia cho in tch :

qFE = (3)

Cng trng in c n v l V/m. 1.4.4. Cng trng t (magnetic field strength - H) Cng trng t l ln ca vct trng ti mt im gy ra bi lc tnh in F ln in tch q chuyn ng vi vn tc v:

F = q(v H) (4) Cng trng t c n v l A/m. 1.4.5. im o (Point of Investigation - PI) im o l v tr nm trong vng o (nh ngha ti mc 1.4.21) ni thc hin o cc gi tr trng in E, trng t H hoc mt cng sut S. 1.4.6. im tham chiu (Reference Point - RP) i vi anten dng tm (panel antenna) th im tham chiu l tm ca tm phn x sau (rear reflector). i vi anten ng hng (omni-directional) th im tham chiu l tm ca anten. Vi cc loi anten khc cn phi quy nh im tham chiu thch hp. 1.4.7. ng bin tun th (Compliance Boundary - CB) ng bin tun th l ng bao xc nh mt vng th tch m ngoi vng mc phi nhim ti bt c v tr no cng khng vt qu mc gii hn phi nhim, khng tnh n nh hng ca cc ngun bc x khc. Vng tun th l vng th tch c bao bi ng bin tun th. 1.4.8. Mt cng sut (power density - S) Mt cng sut l cng sut bc x ti vung gc vi mt b mt, chia cho din tch b mt . Mt cng sut c n v l W/m2. 1.4.9. Mt cng sut sng phng tng ng (equivalent plane wave power density) Mt cng sut sng phng tng ng l cng sut trn mt n v din tch c chun ha theo phng lan truyn ca sng phng trong khng gian t do c biu din bi:

22

120120

HES == (5) 1.4.10. My pht (transmitter) My pht l thit b pht ra cng sut in tn s v tuyn v c ni vi anten cho mc ch truyn thng tin. 1.4.11. Mc gii hn phi nhim (exposure level)

QCVN 78:2014/BTTTT

7

Mc gii hn phi nhim c dng so snh vi cc gi tr phi nhim. Trong di tn s t 300 kHz n 3 GHz, cc mc gii hn phi nhim c th l gi tr cng trng in, cng trng t hoc mt cng sut. 1.4.12. Ngun lin quan (Relevant Source - RS) Ngun lin quan l ngun bc x v tuyn trong di tn s t 300 kHz n 3 GHz c T l phi nhim ln hn 0,05 ti mt im o (PI) xc nh. 1.4.13. Phi nhim (exposure) Phi nhim l hin tng xut hin khi con ngi b t trong trng RF. 1.4.14. Phi nhim do ngh nghip (occupational exposure) Phi nhim do ngh nghip l phi nhim ca con ngi trong cc iu kin c khng ch, xut hin trong khi lm vic v do bn cht cng vic. i tng ny bao gm nhng ngi trng thnh c o to hoc c thng bo nhn bit cc ri ro tim n v thc hin cc bin php phng nga thch hp. 1.4.15. Phi nhim khng do ngh nghip (non-occupational exposure) Phi nhim khng do ngh nghip l phi nhim ca con ngi, khng phi do trong khi lm vic hoc do cng vic. i tng ny bao gm ngi mi la tui v mi tnh trng sc kho khng nhn bit c s phi nhim ang din ra. 1.4.16. Thit b cn o kim (Equipment Under Test EUT) Thit b cn o kim (EUT) l i pht thanh, i truyn hnh cn phi o kim theo phng php quy nh trong Quy chun ny. 1.4.17. Tnh ng hng (isotropy) Tnh ng hng l c tnh vt l khng thay i trong mi hng. 1.4.18. Tr khng khng gian t do (intrinsic impedance of free space) Tr khng c tnh l t s gia cng trng in vi cng trng t ca sng in t lan truyn trong khng gian. Tr khng c tnh ca sng phng trong khng gian t do (tr khng khng gian t do) xp x bng 377 (hay 120 ). 1.4.19. T l phi nhim (Exposure Ratio - ER) T l phi nhim l thng s c nh gi ti mt v tr xc nh cho mi tn s hot ng ca ngun pht v tuyn. Trong di tn s t 300 kHz n 10 MHz:

2

=

LEEER hoc

2

=

LHHER (6)

Trong di tn s t 10 MHz n 3 GHz: 2

==

LL EE

SSER (7)

trong : - ER: T l phi nhim ti mi tn s hot ng ca ngun; - f : tn s hot ng ca ngun; - S: mt cng sut sng phng tng ng o c ti tn s f ca ngun;

QCVN 78:2014/BTTTT

8

- SL: mc gii hn phi nhim dn xut di dng mt cng sut sng phng tng ng ti tn s f; - E: cng trng in o c ti tn s f ca ngun; - EL: mc gii hn phi nhim dn xut di dng cng trng in ti tn s f; - H: cng trng t o c ti tn s f ca ngun; - HL: mc gii hn phi nhim dn xut di dng cng trng t ti tn s f. 1.4.20. T l phi nhim tng cng (Total Exposure Ratio - TER) T l phi nhim tng cng l tng cc gi tr t l phi nhim ca EUT v tt c cc ngun lin quan trong di tn s t 300 kHz n 3 GHz:

TER = EREUT + ERRS (8) trong : - EREUT: T l phi nhim ca EUT; - ERRS: T l phi nhim ca tt c cc ngun lin quan. 1.4.21. Vng o (Domain of Investigation - DI) Vng o l phn vng ca vng lin quan ni ngi dn c th tip cn khi i pht thanh, truyn hnh c a vo hot ng. 1.4.22. Vng lin quan (Relevant Domain - RD) Vng lin quan l vng xung quanh anten, trong t l phi nhim do anten gy ra ln hn 0,05. 1.4.23. Vng thm nhp (Public Access - PA) Vng thm nhp l ni c th din ra cc hot ng i li, sinh hot trong iu kin bnh thng ca ngi dn. 1.5. K hiu v ch vit tt 1.5.1. K hiu

Cng trng in E Vn trn mt (V/m) Cng trng t H Ampe trn mt (A/m) Mt cng sut S Ot trn mt vung (W/m2)

Tn s f Hc (Hz) Bc sng Mt (m) Vn tc nh sng trong chn khng c 2,997 x 108 m/s Tr khng khng gian t do 0 120 (~ 377 )

1.5.2. Ch vit tt AM Amplitude Modulation iu ch bin CB Compliance Boundary ng bin tun th DI Domain of Investigation Vng o EIRP Equivalent Isotropic Radiated

Power Cng sut bc x ng hng tng ng

QCVN 78:2014/BTTTT

9

ER Exposure Ratio T l phi nhim EUT Equipment Under Test Thit b cn o kim FM Frequency Modulation iu ch tn s MF Medium Frequency Tn s trung bnh PA Public Access Vng thm nhp PI Point of Investigation im o RD Relevant Domain Vng lin quan RP Reference Point im tham chiu RS Relevant Source Ngun lin quan TER Total Exposure Ratio T l phi nhim tng cng VHF Very High Frequency Tn s rt cao UHF Ultra High Frequency Tn s siu cao

2. QUY NH K THUT 2.1. Gii hn phi nhim khng do ngh nghip Gii hn phi nhim khng do ngh nghip i vi cc tn s v tuyn in phi ph hp vi gii hn quy nh ti mc 6.3 ca TCVN 3718-1:2005, c th nh sau:

Bng 1 - Mc gii hn phi nhim khng do ngh nghip

Di tn (MHz) Cng trng in E (V/m)

Cng trng t H (A/m)

Mt cng sut S (W/m2)

0,3 n 1 87 0,23/f0,5 (+)

1 n 10 87/f0,5 0,23/f0,5 (+)

10 n 3 000 27,5 0,073 2

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

2.2. Quy nh v T l phi nhim tng cng TER T l phi nhim tng cng ti mt im o bt k khng c ln hn 1.

ffa sdfgfg

QCVN 78:2014/BTTTT

10

3. PHNG PHP O 3.1. M t phng php Phng php xc nh T l phi nhim tng cng c th hin nh lu Hnh 1.

Hnh 1 - Lu o kim phi nhim ti hin trng

C tn ti vng o?

Bc 1: Kho st hin trng

BT U

Bc 2: Tnh ton xc nh vng tun th

Bc 3: Tnh ton xc nh vng lin quan v vng o

Bc 4: Xc nh im o v thc hin o xc nh TER

TER 1 ?

KT THC

TER 1 trong DI TER >1 trong DI

ng

Khng

C

Sai

C

Khng

Xc nh vng tun th c giao ct vng

thm nhp?

QCVN 78:2014/BTTTT

11

Lu minh ha trong Hnh 1 nhm xc nh T l phi nhim tng cng c thc hin theo 4 bc nh sau: - Bc 1: Kho st hin trng. Trc khi thc hin tnh ton th vic kho st

hin trng cn c thc hin thu thp cc thng tin c bn ca i pht thanh, truyn hnh. C th phi thu thp thng tin v cc tham s nh chiu cao ca ct anten so vi mt t, kiu anten, gc ngng c, gc ngng in, h s tng ch, biu bc x (c trng in E v trng t H), di tn hot ng, cng sut a vo anten (hoc cng sut pht v cc suy hao),

- Bc 2: Tnh ton xc nh vng tun th ca i pht thanh, truyn hnh theo 3.3.1. Nu ngi dn c th tip cn khng gian trong ng bin tun th (vng tun th) th T l phi nhim tng cng s ln hn 1.

- Bc 3: Tnh ton xc nh vng lin quan, vng thm nhp v vng o theo 3.3.2, 3.3.3 v 3.3.4. Nu ngi dn khng c kh nng tip cn vo vng lin quan, ngha l khng tn ti vng o, th T l phi nhim tng cng s nh hn hoc bng 1.

- Bc 4: Nu ngi dn c kh nng tip cn vo vng lin quan th thc hin xc nh im o v nh gi T l phi nhim tng cng theo 3.2.

3.2. nh gi ton din T l phi nhim tng cng Vic nh gi ton din T l phi nhim tng cng nhm xc nh T l phi nhim tng cng ln nht trong cc khu vc lin quan ni m ngi dn c th tip cn (vng o). Nu n v ch s hu, ch qun l i pht thanh, truyn hnh thit lp ranh gii ca khu vc cm (restricted area) nhm ngn s tip cn ca ngi dn ti khu vc xung quanh EUT v/hoc cc ngun lin quan th vic nh gi phi c thc hin ti cc im o nm st vi cc ranh gii ny.

Hnh 2 - V tr o ti tng im o

QCVN 78:2014/BTTTT

12

T l phi nhim tng cng c xc nh ti cc im o bng phng php m t trong 3.4. Khong cch gia cc im o ti a l 2 m. Tp hp cc im o phi to thnh li vi mt li l hnh vung c kch thc ti a l 2 m x 2 m. Ti mi im o, T l phi nhim tng cng c xc nh l gi tr ln nht ca cc gi tr T l phi nhim tng cng o c ti cc v tr o c cao so vi mt sn ni ngi dn tip cn l 110 cm, 150 cm v 170 cm v nm trong vng o nh minh ha trong Hnh 2. 3.3. Phng php xc nh cc vng 3.3.1. Vng tun th 3.3.1.1. Vng tun th ca anten i pht thanh AM bng MF, tn s t 526,25 - 1606,5 kHz: Vng tun th ca anten pht thanh AM bng MF l mt hnh tr c trc trng vi trc ca anten, chiu cao bng chiu cao ca anten, bn knh c xc nh bng cng thc di y:

L

EIRP

EP

R30= (9)

Trong R(m) l bn knh vng tun th tnh t tm anten, PEIRP(W) l cng sut bc x ng hng tng ng ca i pht thanh MF, EL(V/m) l mc gii hn cng trng theo quy nh Bng 1. 3.3.1.2. Vng tun th ca anten i pht thanh FM (54 - 68 MHz, 87 - 108 MHz), L (1452 1492 MHz) v anten i truyn hnh VHF (174 - 230 MHz), UHF (470 - 806 MHz): a) Vng tun th ca anten ng hng: Vng tun th ca anten ng hng l mt hnh tr bao quanh anten c trc trng vi trc ca anten v c chiu cao bng vi chiu cao mt bc x ca anten cng vi mt khong h1 v hai pha ca anten v c xc nh nh sau: - Bn knh vng tun th c xc nh theo cng thc:

L

EIRP

SPR 4= (10)

Trong : R(m): bn knh vng tun th tnh t mp ngoi ca anten. PEIRP (W): cng sut bc x ng hng tng ng ca anten.

SL(W/m2): mc gii hn phi nhim dn xut di dng mt cng sut sng phng tng ng ti tn s f, gi tr ca SL nh quy nh ti Bng 1.

- Chiu cao vng tun th c xc nh theo cng thc: H = h + 2h1 (11)

Trong :

H(m): chiu cao ca vng tun th. h(m): chiu cao mt bc x ca anten. h1(m): chiu cao phn m rng, c xc nh theo cng thc:

QCVN 78:2014/BTTTT

13

tgRh =21 (12)

Vi R l bn knh vng tun th, l gc m ca bp sng ca anten c xc nh da trn biu pht x ng ca anten. Gc m ca bp sng c xc nh bng gc gia trc ca bp sng v hng m cng trng trn hng y bng 50% (gim 3dB) so vi cng trng nm trn trc chnh ca bp sng. Trng hp bp sng ca h thng anten c thit k c gc ngng (beam tilt) th phi cng thm gc ngng vo gc tnh h1 trong cng thc (12).

Hnh 3 - Hnh v cc gi tr tnh ton chiu cao vng tun th ca anten

QCVN 78:2014/BTTTT

14

Hnh 4 - Biu bc x ng ca anten xc nh gc m ca bp sng

b) Vng tun th ca anten nh hng:

Hh

h1

h1

D

Anten

Hnh 5 - Vng tun th ca anten nh hng

Vng tun th ca mt anten nh hng l mt hnh tr trn, c ng knh D, trc song song vi trc ca anten v c chiu cao bng vi chiu cao mt bc x ca anten cng vi mt khong h1 v hai pha trn v di ca anten v c xc nh nh sau: - ng knh vng tun th c xc nh theo cng thc:

Gc nghing Gc so vi phng ngang ()

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

0

QCVN 78:2014/BTTTT

15

L

EIRP

SPD 4= (13)

Trong : D(m): ng knh vng tun th tnh t mp ngoi ca anten. PEIRP (W): cng sut bc x ng hng tng ng ca anten.

SL(W/m2): mc gii hn phi nhim dn xut di dng mt cng sut sng phng tng ng ti tn s f, gi tr ca SL nh quy nh ti Bng 1.

- Chiu cao vng tun th c xc nh nh cng thc (11). 3.3.1.3. Vng tun th ca i pht thanh, i truyn hnh c nhiu anten Nu i pht thanh, i truyn hnh c nhiu anten pht th vng tun th ca i pht thanh, i truyn hnh l tp hp cc vng tun th ca cc anten thnh phn. 3.3.2. Vng lin quan ng bin ca vng lin quan ca mt anten c xc nh bng cch nhn nm (05) ln khong cch tnh t im tham chiu ca anten n ng bin vng tun th ca anten theo mt hng xc nh (chi tit nh Hnh 6 v Hnh 7).

5R

H

R

Anten Vng tun th

Vng lin quan

5(h/2+h1)

5(h/2+h1)

Hnh 6 - Vng lin quan ca anten ng hng

QCVN 78:2014/BTTTT

16

5D

H

D

AntenVng tun

th Vng lin quan

5(h/2+h1)

5(h/2+h1)

Hnh 7 - Vng lin quan ca anten nh hng

3.3.3. Vng thm nhp Vng thm nhp c xc nh bi mt (hoc nhiu) khng gian c y l mt sn ni ngi dn tip cn v chiu cao l 170 cm. 3.3.4. Vng o Vng o l vng con ca vng lin quan ni ngi dn c th tip cn, l phn giao nhau gia vng lin quan v vng thm nhp ca i pht thanh, truyn hnh (xem minh ha ti Hnh 8).

Hnh 8 - Minh ha vng o

Vng tun th

Anten

QCVN 78:2014/BTTTT

17

3.4. Phng php o v xc nh gi tr T l phi nhim tng cng 3.4.1.Yu cu chung C th s dng cc thit b o bng thng rng hoc thit b o chn tn bao gm mt hoc nhiu u o trng in E hoc trng t H xc nh T l phi nhim ER. Trong trng hp s dng u o khng ng hng, php o phi c thc hin theo cc hng o khc nhau nhm m bo tnh ng hng. V d vi trng hp s dng anten lng cc, cc php o phi c thc hin theo 3 hng trc giao trong khng gian. Trong trng hp s dng u o ng hng, ch cn thc hin 1 php o duy nht. i vi thit b o chn tn th mc cng trng in nh nht o c phi nh hn hoc bng 0,05 V/m v mc ln nht o c phi ln hn hoc bng 100 V/m. i vi thit b o bng thng rng th mc cng trng in nh nht o c phi nh hn hoc bng 1 V/m v mc ln nht o c phi ln hn hoc bng 100 V/m. 3.4.2. Php o T l phi nhim 3.4.2.1. Yu cu c bn Ty thuc vo iu kin c th ca php o th c th s dng thit b o bng thng rng hoc chn tn. Thng thng cc php o chn tn cho kt qu o T l phi nhim chnh xc hn. Kt qu nh gi T l phi nhim s dng thit b o bng thng rng theo 3.4.2.2 s vt qu gi tr thc t. Khong cch gia u o v ngi thc hin o hoc cc vt phn x ti thiu phi l 20 cm. Tham s o: - Trng hp v tr o nm trong vng trng gn ca anten (l vng nm trong

hnh cu c tm l anten, bn knh l r = /2 vi trng hp bc sng ln hn chiu di mt bc x hoc r= 2d2/ vi trng hp bc sng nh so vi chiu di mt bc x, l bc sng v d l kch thc ln nht ca mt bc x ca anten) th thc hin o c hai tham s: cng in trng E, cng t trng H.

- Trng hp v tr o nm trong vng trng xa ca anten th c th thc hin o mt trong cc tham s: cng in trng E, cng t trng H hoc mt cng sut S.

3.4.2.2. iu kin p dng php o bng thng rng a) Mt ngun bc x v tuyn tri Thit b o bng thng rng c th c s dng xc nh T l phi nhim v T l phi nhim tng cng trong trng hp c mt ngun bc x v tuyn tri. Mt ngun v tuyn c coi l tri nu c th chng minh rng tng cng sut ca cc ngun bc x khc nh hn 13 dB so vi cng sut ngun (c th s dng phng php o ph). b) nh gi qu mc mc phi nhim

QCVN 78:2014/BTTTT

18

Nu gi tr o c thp hn 13 dB so vi mc gii hn phi nhim thp nht c p dng th gi tr TER s nh hn 1 k c khi tnh n s thay i v cng sut trong i pht thanh, truyn hnh. 3.4.2.3. iu kin p dng php o chn tn Thit b o chn tn c s dng xc nh T l phi nhim v T l phi nhim tng cng i vi trng hp trong di tn cn o c mc gii hn phi nhim khc nhau. Cng trng o c lin quan n mt ngun bc x v tuyn phi bao hm tng cng sut ca tn hiu. Do vy bng thng phn gii ca thit b o phi rng hn bng thng chim dng ca tn hiu. Trong trng hp tn hiu c ph tn s rng hn bng thng phn gii th p dng phng php cng tch ly tng cng sut, c tnh n hnh dng ca b lc bng thng phn gii (thng c gi l ch o cng sut knh Channel Power mode). i vi tn hiu c h s nh (crest factor) ln th khng nn s dng b tch sng nh (peak detector) v c th gy ra s sai lch ln. 3.4.3.Xc nh gi tr T l phi nhim tng cng Nu s dng phng php o bng thng rng o T l phi nhim tng cng trong ton b di tn s t 300 kHz n 3 GHz (mc 3.4.2.2) s thu c trc tip gi tr TER. Nu s dng phng php o chn tn, trng hp trong ton b di tn s t 300 kHz n 3 GHz c N ngun bc x n tn, T l phi nhim ca mi ngun o c theo phng php chn tn (mc 3.4.2.3) l ERi th gi tr TER s l:

RSEUT

N

ii ERERERTER +==

=1 (14)

Theo quy nh ti 3.2, ti mi im o gi tr TER c xc nh ti 3 v tr v ly gi tr ln nht. 3.5. nh gi t l phi nhim tng cng Nu T l phi nhim tng cng nh hn hoc bng mt (TER 1) th i pht thanh, truyn hnh tun th yu cu v mc gii hn phi nhim khng do ngh nghip. Nu T l phi nhim tng cngln hn mt (TER > 1) th i pht thanh, truyn hnh khng tun th yu cu v mc gii hn phi nhim khng do ngh nghip.

4. QUY NH V QUN L

4.1. Cc i pht thanh, truyn hnh thuc phm vi iu chnh ti mc 1.1 phi tun th cc yu cu quy nh ti Quy chun ny. 4.2. Mc gii hn phi nhim quy nh ti mc 2.1 ca Quy chun ny dn chiu t mc 6.3 ca TCVN 3718-1:2005. Trng hp TCVN 3718-1:2005 c s thay i hay cp nht th p dng theo tiu chun tng ng.

5. TRCH NHIM CA T CHC, C NHN

Cc c quan, t chc c hot ng pht tn hiu pht thanh, truyn hnh phi m bo ph hp vi Quy chun ny v chu s kim tra ca c quan qun l nh nc theo cc quy nh hin hnh.

QCVN 78:2014/BTTTT

19

6. T CHC THC HIN

6.1. Cc Vin thng v cc S Thng tin v Truyn thng c trch nhim hng dn v t chc trin khai qun l cc i pht thanh, truyn hnh theo Quy chun ny. 6.2. Trong trng hp cc quy nh nu ti Quy chun ny c s thay i, b sung hoc c thay th th thc hin theo quy nh ti vn bn mi.

QCVN 78:2014/BTTTT

20

PH LC A (Tham kho)

Xc nh vng tun th ca i pht thanh FM, i pht thanh bng L v i truyn hnh VHF, UHF

A.1. Xc nh ng knh ca vng tun th

Hnh A.1 biu din mt ct ngang (vung gc vi trc anten) ca vng tun th ca anten ng hng qua im tham chiu ca anten (xem 1.4.6).

Hnh A.1 - Mt ct ngang ca vng tun th qua im tham chiu

Chn im A l im bt k nm trn ng bin tun th ca anten ng hng (xem Hnh A.1). p dng m hnh truyn sng trong khng gian t do, vi gi thit ti im bt k trn ng bin tun th ca anten ng hng c c tnh bc x trng xa, mt cng sut ti im A s l:

24 RPS EIRPA = (W/m

2) (15)

trong :

- EIRPP (W): cng sut bc x ng hng tng ng ca anten;

- R (m): khong cch t im tham chiu (RP) n im A (chnh bng bn knh ca vng tun th);

- AS (W/m2): mt cng sut ti im A.

Theo nh ngha ng bin tun th th mt cng sut ti im A bng mc gii hn phi nhim dn xut di dng mt cng sut, LA SS = . V vy:

L

EIRP

SPR 4= (m) (16)

A.2. V d tnh ton kch thc vng tun th

Mc ny nu mt v d tnh ton kch thc vng tun th cho mt anten ng hng. Gi thit mt anten i truyn hnh UHF loi ng hng c cc thng s sau:

Anten

A

R

Anten

A

R

QCVN 78:2014/BTTTT

21

- Tn s hot ng: Knh 21: 470 478 MHz - Cng sut my pht: P = 5 kW (cng sut ti u vo h thng anten) - li tng th ca anten: G = 10,50 dBi - Tng cng cc thnh phn suy hao: L = 1,5 dB - di mt bc x ca anten h = 4,8 m

- Beam tilt: 0,50 (t = 0,50) - Gc m ca bp sng (gc gia trc ca bp sng v hng m cng

trng trn hng y bng 50% so vi cng trng nm trn trc ca bp sng - Hnh A.2): 2,20((m = 2,20)

- Mc gii hn phi nhim khng do ngh nghip (dn xut di dng mt cng sut sng phng tng ng) ti tn s pht ca anten SL= 2 W/m2;

Hnh A.2 - th bc x theo chiu ng Cng sut bc x ng hng tng ng: p dng cng thc (2):

PEIRP = P 10(G-L)/10 = 5 100,9 = 39,72(kW)

Bn knh ca vng tun th: p dng cng thc (10):

8,39214,34

100072,394

===

L

EIRP

SPR (m)

Gc so vi phng ngang ()

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

0

QCVN 78:2014/BTTTT

22

Chiu cao ca vng tun th: p dng cng thc (11) v (12):

+ Chiu cao vng m rng:

h1 = (R/2)tg = (39,8/2)tg(2,20 + 0,50) = 19,90,047 = 0,94 (m) + Chiu cao vng tun th:

H = h + 2h1 = 4,8 + 20,94 = 6,68 (m).

A.3. Hnh v minh ha vng tun th

Hnh v A.3 di y minh ha vng tun th ca mt i pht thanh, truyn hnh s dng anten ng hng. Vng tun th ca anten ny l mt hnh tr, c trc trng vi trc anten,bn knh bng bn knh vng tun th, chiu cao bng chiu cao vng tun th.

Hnh A.3 - Minh ho vng tun th ca i pht thanh, truyn hnh s dng anten ng hng

QCVN 78:2014/BTTTT

23

PH LC B (Tham kho)

Xc nh ng bin ca vng lin quan ca i pht thanh FM, i pht thanh bng L v i truyn hnh VHF, UHF

Ph lc ny din gii cch xc nh ng bin ca vng lin quan bng cch nhn 5 ln khong cch gia im tham chiu ca anten v ng bin tun th theo mt hng xc nh. Vic xc nh ng bin ca vng lin quan da trn ng bin tun th p dng cc gi thit sau: a) Ti im bt k trong trng xa ca trng bc x, cng trng in t l

nghch vi khong cch t im n anten bc x; b) Ti mi tn s, T l phi nhim t l vi bnh phng cng trng in.

Hnh B.1 - Xc nh bin vng lin quan

Xt ti im PCB cch anten khong cch l d, gi tr cng trng in o c l dE . Nu Ld EE = (l gi tr mc gii hn phi nhim dn xut di dng cng trng in) th theo nh ngha ng bin tun th (mc 1.4.7), im PCB s nm trn ng bin tun th v T l phi nhim ti im ny s bng 1 v:

2

=

L

dd E

EER (17)

Ti im PRD cch anten khong cch 5d, cng trng in tng ng s l Ed/5 v T l phi nhim tng ng l:

255

2

d

L

dr

ERE

EER =

= (18)

T l ny (0,04) nh hn vi quy nh v gii hn ca vng lin quan (mc 1.4.22) l 0,05 v do ti v tr ny, anten ang xt khng cn c coi l ngun lin quan. Tp hp cc im PRD s to thnh bin ca vng lin quan.

Ant

en

0 d 5d

Khong cch t anten

Cng trng in = Ed T l phi nhim = ERd Cng trng in = Ed/5

T l phi nhim = ERd/25

PCB - im nm trn CB PRD - im nm trn ng bin ca RD

QCVN 78:2014/BTTTT

24

TH MC TI LIU THAM KHO

[1] TCVN 3718-2: 2007 Qun l an ton trong bc x tn s Radio - Phn 2: Phng php khuyn co o trng in t tn s radio lin quan n phi nhim ca con ngi di tn t 3 kHz n 300 GHz.

[2] CENELEC EN 50400 (June 2006) Basic standard to demonstrate the compliance of fixed equipment for radio transmission (110 MHz 40 GHz) intended for use in wireless telecommunication networks with the basic restrictions or the reference levels related to general public human exposure to radio frequency electromagnetic fields, when put into service.

[3] IEEE Std C95.1-2005 IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz.

[4] IEEE STANDARD C95.3-2002 - IEEE Recommended Practice for Measurements and Computations of Radio Frequency Electromagnetic Fields With Respect to Human Exposure to Such Fields, 100 kHz-300 GHz.

[5] OET Bulletin 65 - Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields - Edition 97-01 - August 1997.

[6] Industry Canada. GL-01 (10/2005) - Guidelines for the Measurement of Radio Frequency Fields at Frequencies from 3 kHz to 300 GHz.

[7] TN-261 (2/2011) - Safety Code 6 (SC6) Radio Frequency Exposure Compliance Evaluation Template (Uncontrolled Environment Exposure Limits).

[8] TN-329 (2/2011) - Safety Code 6 (SC6) Measurement Procedures (Uncontrolled Environment).