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FM Band Transmitter Specs - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


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

Captain


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 ).


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Guest
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!


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

Captain


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

http://rfcafe.com/phpBB2/posting.php?mode=reply&t=1833



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