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[Discuss-gnuradio] Broadcast FM is crap!

From: Marcus D. Leech
Subject: [Discuss-gnuradio] Broadcast FM is crap!
Date: Sun, 19 Feb 2012 11:50:48 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16

Spent some time yesterday evening building up a stereo FM receiver in GRC. I know there are already a few of these for broadcast FM,
  but for personal education reasons, I thought I'd build something up.

Attached is my result.

It seems to work reasonably well (better than the existing example WFM stereo receiver on the same signals).

But something I've discovered is that about 30% of the program material coming out of my fave radio station doesn't even have any L-R signal present. I mean, I can understand during announcements, commercials, etc. But a lot of the musical material
  doesn't have any L-R, even modern material.

But I never really knew the gory details of FM Multiplex before--didn't know the L-R channel was DSB-SC, for example. Never had cause to think deeply about it. I knew there was a 19kHz pilot tone, and that it was doubled to 38kHz (usually with a PLL), but I always thought
  it was used as a switching signal of some sort.

If I get keen, I'll extend this to include RDS decoding.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

Attachment: simple_fm_rcv.grc
Description: application/gnuradio-grc

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