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Question on Legal Frequencies and Transmitter Power
http://www.rcsail.com/forum/viewtopic.php?f=3&t=694		 Page 1 of 1
Author:  andy2667 [ Sun Feb 26, 2006 12:20 pm ]
Post subject:  Question on Legal Frequencies and Transmitter Power
Hello,

I am a newbie and just started to play RC electric Helis, planes and going to start RC Sailplanes. I noted from the following link that some frequencies are excempted from licencing:

http://www.hkrcss.org/ofta_license_exempt.jpg

Without noting the radiation power restrictions, I just bought a Futaba 6EXH transmitter with 35Mhz Band and selected the frequency of 35.170 falling within the exccempted frequencies range.

I can't find the radiation power specification even I have searched through the Fubata-RC site. Do the normal 35MHz band Fubata/JR transmoitters comply with the Ratiation power limit of 100mw stated in OFTA letter?

If the transmitters normally available in the market have radiation powers exceed the power limit of 100mw imposed on 35MHz band & 40MHz bands, I may consider to change to 75MHz band in my future upgrade.

My reasoning of selecting 35MHz band is that bothe JR & Futaba are compatable to each other for 35/36MHz & 40/41MHz bands. This allow me some flexibilities in selecting receivers and future upgrading choices.I might have made the wrong decision. It seems that the 34/36 and 40/41 bands may not be legal in terms of radiation power. Also, the 35MHz band is not common in China & Hong Kong limiting my future upgrade.

Thanks

Andy
Author:  Y C Lui [ Sun Feb 26, 2006 1:39 pm ]
Post subject: 
呢個問題其實以前都討論過﹐OFTA 定既發射功率標準其實都係抄其他國家﹐譬如 35MHz 係歐洲果邊用多﹐果邊限制 100mW, 所以 OFTA 就定 100mW, 72 MHz 就係美國用為主﹐美國定 750mW, OFTA 就照跟﹐原因好簡單﹐因為有人 challenge 起上黎 OFTA 都可以話有其他國家用緊。我都上過德國D 大forum 問過﹐果邊D人真係用緊 100mW :

http://www.rclineforum.de/forum/thread. ... post562713

至于香港買到D 35/ 40 MHz 遙控到底係咪 100mW 就要睇果D遙控係原本為邊個市場生產﹐如果係為歐洲果邊( 多數係 )﹐ 咁發射功率就應該係 100mW, 即係合法。但詳情都係要問入口商至知。香港市場咁細﹐廠家多數唔會特登生產符合香法例既遙控。
Author:  ken [ Sun Feb 26, 2006 2:19 pm ]
Post subject: 
Andy,

We have this discuss about one and helf years ago. You can check the stanley's forum:

http://www.rcsail.com/forum/viewtopic.p ... c&start=15

Or the following:
http://www.rcuniverse.com/forum/m_20985 ... tm#2124177


The summary from Futaba is:


The 500mW limit used in the US is measured 3 meters from the transmitter. The 100mW limit used in other countries is measured at 10 meters. Although the US output power is rated greater, it is actually similar to the 100mW limit used in other countries, but they are just measured at different distances.

I hope you find this information helpful. You can also reach our Futaba support technical team at 217-398-8970, or via fax at 217-398-7721.

Sincerely,
Krysta
Lead Futaba Customer Service and Programming Technician
Author:  andy2667 [ Sun Feb 26, 2006 4:09 pm ]
Post subject: 
Hi Ken & YC,

Very useful information. It seems that I longer need to concern about the Radiation Power of my transmitter & I will be hapily stick to my planned 35MHz band strategy.

Thanks

Andy
Author:  CM Cheng [ Sun Feb 26, 2006 6:30 pm ]
Post subject: 
ken wrote:
. . . . .
The 500mW limit used in the US is measured 3 meters from the transmitter. The 100mW limit used in other countries is measured at 10 meters.
. . . . .


Output power, 咁度既 :?:
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