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Topic: Transmitting iphone music via Fm transmitter (Read 617 times) previous topic - next topic

allanhurst

#15
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.

Allan

Grumpy_Mike

#16
Sep 13, 2017, 05:10 am Last Edit: Sep 13, 2017, 05:15 am by Grumpy_Mike
Quote
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:-
Quote
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.

Noobian

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

JMD1

Who cares if its illegal? Just buy 1 transmitter, set a frequency, get 30+cm antenna, tell a friend to go a far far away, and test if there is signal. How would care for legality? Its EU here and I dont mean Germany of France or any big country :D Just do your fun.
All i recommend is to buy a more powerful FM transmitter. I doubt that little guy will perform well over distance as ther are many interruptions.

aarg

#19
Jan 09, 2018, 09:26 pm Last Edit: Jan 09, 2018, 09:31 pm by aarg
Who cares if its illegal?
Come on, it's not "big brother". The regulations are there to ensure that the valuable resource of the EM spectrum is protected from harmful interference and can be effectively used and shared.

Commercial FM licenses are carefully allocated by transmitter location, so as to minimize interference between stations using the same frequency, or close frequency. The only place where it actually doesn't matter much is in vast rural areas because there are so few stations due to the fact of barely beyond the horizon propogation.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

Grumpy_Mike

Who cares if its illegal? ....... How would care for legality? Its EU here and I dont mean Germany of France or any big country.
So for one I care, if you want to play about with transmitters then their are legal ways to do it in the form of ham radio. You are too stupid to know of any RF pollution you can generate and it could cost a life if you interfere with things like rescue communications. It seems like you want to have the advantages of EU protection without the responsibility of obeying the law. The fact that you believe you are not likely to get caught is a morally corrupt undefensible stance.

MrMark

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?
In the US (and apparently Canada) one can buy wireless FM transmitters like the circuit in post #1 in kit form.

e.g. : https://www.canakit.com/fm-transmitter-for-beginners-kit-ck017-uk017.html

Unless one deviates from the circuit design, the power output will be limited.  I built these sorts of kits as a kid.

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