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Topic: Transmitting iphone music via Fm transmitter (Read 339 times) previous topic - next topic


Sep 13, 2017, 02:03 am Last Edit: Sep 13, 2017, 02:59 am by allanhurst
Didn't know the FCC permitted small untested unlicensed tx's - presumably only in certain bands. Not true in the UK.  Even in the US wouldn't it be wise to have somebody measure the power before using it to avoid problems?

Presumably the ham got a slap - ham bands don't include FM broadcast!

I wouldn't quote a measurement like '176,526 microvolts on 90.9 MHz'. What does it mean?

 Even with precision lab gear and calibrated cable connections we're suspicious of anything closer than +/- 0.5dB , never mind an open - air link with possible reflections etc. Anechoic chambers maybe a bit better.

I don't think the OP will get a 3km range with a transmitter that only gives 250uV/m at 3m.

Try the inverse square law - that'll be 10^6 times less...

Not much.



Sep 13, 2017, 05:10 am Last Edit: Sep 13, 2017, 05:15 am by Grumpy_Mike
Didn't know the FCC permitted small untested unlicensed tx's
Yes they do as a sort of sop to "freedom of expression". However in practice the regulations are such that you need to know a hell of a lot in order to demonstrate you are within the limits.

This is the FCC document.

I like this bit:-
Furthermore, if the Commission determines that the operator of such a transmitter has not attempted to ensure compliance with the Part 15 technical standards by employing good engineering practices then that operator may be fined up to $10,000 for each violation and $75,000 for a repeat or continuing violation.


$10,000 !   So much for his Pirate Radio.

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