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Old Dec 18, 2005, 05:40 PM
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What is the maximum output for 2.4 GHz?

Does anyone know what the maximum power output on a 2.4 GHz transmitter is before you need a license?

Thanks
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Old Dec 18, 2005, 07:47 PM
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Don't quote me but I think it's only 10 milliwatts (mw) Not very much at all.
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Old Dec 18, 2005, 08:38 PM
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1 Watt - I can't remember my source, but I recall that being it....

Most are significantly under that.
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Old Dec 18, 2005, 09:53 PM
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For license free use in the USA, the video Tx's Effective Radiated Power is less than 1mW (.001W) and the Tx must have a valid FCC Part 15 Reg ID label on it. Otherwise, it will need to conform to the amateur radio rules.

Some European communities are allowed about 10mW. FCC Part 15 approved Spread Spectrum transmitters can have higher native RF power, up to one watt or so. But, they use trickery to get around the low power ERP limits.
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Old Dec 19, 2005, 12:21 PM
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I dont buy that .001 w ( 1 mW ). ALmost all equipment manufactured has more output power than that. Even cordless phones radiate more than 1 mw. I dont remember what the exact number is, but its definately more than 1 mw.

I suspect that MrRCCam misread the rule, that I am guessing states, that IF the output is more than 1 mw, the transmitter must have the FCC sticker on it. This is NOT the same as needing a license
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Old Dec 19, 2005, 01:09 PM
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I'm not a tech but this may be the information you're looking for.

Compliance tables power levels in different regions

How much power do I need to microwave the cat
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Old Dec 19, 2005, 01:14 PM
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Sorry, but I am correct. For license free use of FCC Part 15 transmitters, the output must be less than 500mV/meter at 3 meters {non-spread spectrum designs}. This is the practical equiv of less than 1mW being radiated from the antenna. In the typical 2.4Ghz consumer design, about 4mW will be driven into the patch antenna element, and due to feedline losses, the output is usually less than 300mV/meter at 3 meters (well within the spec to avoid violations).

Quote:
Even cordless phones radiate more than 1 mw.
Consumer cordless phones, that are not digital spread spectrum, are under 1mW ERP. That is plenty for 100 meters of reliable range (which is the intent of cordless phone app) using a Rx with good uV sensitivity. Consumer Spread Spectrum designs can utilize up to about 1W of native RF power and a bit more EIRP is allowed (ref Part 15 rule 15.247). But, their Effective Radiated RF power is assumed to be 0W due to the way the FCC allows the mfg to measure such signals.

The 47 CFR Part 15 regs are available for download on the FCC's web site. These are the rules that intentional and unintentional radiators of consumer products must follow if used license free in the USA.

EDIT: I forgot to say that regardless of how much or how little the RF power may be, the transmitter cannot be used license free in the USA unless it is FCC registered for such use. That is the purpose of the FCC ID label on compliant consumer device. BTW, our R/C gear falls under the Part 95 rules, which have different rules than the Part 15 devices. Even so, R/C Tx's have FCC ID's on them too.
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Old Dec 19, 2005, 04:29 PM
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And for 900 MHz the limit without a license is 100 mW, correct?
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Old Dec 19, 2005, 04:40 PM
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900Mhz observes the same rules. That is, if it is not DS Spread Spectrum, then the effective radiated signal must be lesss than 500mV/meter at 3 meters. In practical RF power terms, that is 0.7mW driven into an antenna system with no realized gain. If the antenna system has gain, then the RF power drive must be further reduced to prevent exceeding the limit.

Most importantly, if the Tx is not specifically labeled as FCC Part 15 approved, it isn't license free for use in the USA.
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Old Dec 19, 2005, 06:07 PM
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Why dont you just get a tech licence? It is easy and doesn't cost much. Then you can run a nice downlink
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Old Dec 19, 2005, 06:42 PM
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Quote:
Originally Posted by Mr.RC-CAM
Sorry, but I am correct. For license free use of FCC Part 15 transmitters, the output must be less than 500mV/meter at 3 meters {non-spread spectrum designs}. This is the practical equiv of less than 1mW being radiated from the antenna. .
I stand corrected. I know my wireless router puts out 100 MW, and cordless phone etc. What I did not know was that spread spectrum was allowed more power. Sounds like discrimination to me

Now for my real opinion on the matter, 1 watt at 2.4 GHZ does no go more than a few miles, so you are not going to be bothering anyone unless you are flying over New York City.... I am a ham, but if I did not have a license, I would run my transmitter when needed and not worry about it. It just wont make any difference to anyone.
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Old Dec 20, 2005, 03:31 PM
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you can use 3W at 2.4 G,,

mobile phones use >2W too ...
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Old Dec 20, 2005, 04:19 PM
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Quote:
mobile phones use >2W too ...
FWIW, USA Mobile phones are FCC Part 22 devices. Totally different rules.

As mentioned before, in the USA a "legal" license-free wireless video system would need to follow the Part 15 rules. These federal regulations are online for public review on the FCC web site. Everything needed to answer the OT question is in there.
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Old Dec 20, 2005, 06:26 PM
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Quote:
Originally Posted by crashingagain
Why dont you just get a tech licence? It is easy and doesn't cost much. Then you can run a nice downlink
I agree. Just study, take the test (not that hard) and then you can run a good system and not have to worry about being illegal. I can highly recommend the Gordon West audio cd's and study guide. I got them, studied the book a little and listened to the cd's in the truck at work. Took the test and only missed one question.(Thanks to Gordon West) I think it costs about $14 for the test, around $50 for the study guide and cd's. If you don't want to buy the study guide materials, you can download the question pool from the FCC for free, I believe.

Randy
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