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FM Band Transmitter Specs - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

FL Techie
Post subject: FM Band Transmitter Specs Posted: Tue Oct 11, 2005 4:33 pm


Joined: Tue Jan 06, 2004 1:51 pm
Posts: 8
Sorry for posting in multiple places, but I need this in a hurry.

Does anyone know exactly what FCC spec governs the output of an FM transmitter? My application is for low power (<1 W), and in fact will be covered by Part 15. However, I want to know the real specification limits for THD, frequency accuracy, L-R channel separation, S/N, etc.

I have spent a couple hours searching the web and the FCC website but CANNOT find it!!!

Thanks a lot guys (and gals, if applicable ).


Post subject: FM SpecsPosted: Wed Oct 12, 2005 5:23 pm
The FCC has only a few real regulations for license-free ("Part 15") use:
1. less than 100 mW power
2. inside the FM band, and harmonics down a reasonable amount (I don't know what it is right off the top of my head.

The rest is up to you. If you want to make a crappy Part 15 stereo transmitter with lots of distortion, poor frequency response, almost no separation, etc. , the FCC won't quibble unless you go outside the band or power limits. If you want to make a state-of-the-art DSP-based stereo transmitter, the FCC won't quibble unless you go outside the band or power limits.

Broadcast station limits are something else. You might look at those for THD, separation, frequency response, distortion, etc. if you want a baseline for comparison.

I know these answers are not what you were hoping for - but they do reflect the regs.

Good Luck!


FL Techie
Post subject: Posted: Thu Oct 13, 2005 7:42 am


Joined: Tue Jan 06, 2004 1:51 pm
Posts: 8
Thanks for the infoGuest. Morton provided the documents I was loking for here.


Posted  11/12/2012

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