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[Discuss-gnuradio] WBFM PLL demodulator block


From: Marcus D. Leech
Subject: [Discuss-gnuradio] WBFM PLL demodulator block
Date: Sat, 07 Apr 2012 19:47:20 -0400
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16

I was doing some experiments with this block this evening, and what I discovered was that it requires a much better-quality signal to produce even half-way decent audio output than my "first principles" FM stereo decoder in my "simple_fm_rcv" application. The PLL block uses a PLL to derive the 38KHz injection tone to re-constitute the carrier for the DSB-SC "L-R" signal. I simply use the pilot tone itself, and
  double it with a multiplier/filter.

On stronger signals, the PLL block works just fine. But on weaker ones, my approach appears to be superior. I wonder why? Not being a real
  DSP guru, I just play one on the Internet :-)


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org





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