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Author Topic: Optimod  (Read 2767 times)
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w2tgr
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« on: March 02, 2019, 11:39:18 AM »

Could someone tell me the difference in the  Optimod FM vs AM.. I am wondering if the FM model could be used on AM
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K8DI
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« Reply #1 on: March 02, 2019, 04:00:27 PM »

Short version:  FM includes the stereo encoder, has a pre-emphasis network. AM does not. Unless it's rather old, AM probably has NRSC filtering. FM does not.  Multiband compression bands are different due to the bandwidth of broadcast FM vs AM (no need to compress/limit 6-15kHz on an AM if you're just going to filter it off).

Can you use it? Sure. You need to disable the 75uS preemphasis, turn off the stereo, and add your own LPF/NRSC type filter on the output.

Ed
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Ed, K8DI, warming the air with RF, and working on lighting the shack with thoriated tungsten and mercury vapor...
K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #2 on: March 02, 2019, 06:06:20 PM »

"Ed, K8DI (fmr. KB8TWH) "

Boy, did you get rid of a giant gorilla on your back...  congrats, Ed  -    Grin

Tom, K1JJ
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
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