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Old January 28th 15, 09:58 PM posted to rec.radio.amateur.homebrew
Michael Black[_2_] Michael Black[_2_] is offline
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First recorded activity by RadioBanter: Mar 2008
Posts: 618
Default 10.7 IF/Detector

On Wed, 28 Jan 2015, nothermark wrote:

I need a simple poor ham's deviation meter. That got me looking at
the IC-7100 receiver sitting in my shack. I could get to the
discriminators but it would be a bit messy. OTOH it has a 10.7 MHz IF
output I could add an amplifier and detector to and feed that to my
O'scope to do what I want for long enough to sort out some problems.
That got me looking for a simple detector circuit. No joy so far. I
would really appreciate any pointers to either a circuit I could
breadboard or a canned solution. I was thinking I'd go commercial and
add some gain for a better look the narrow bandwidths used in
communications gear but anything that will work with normal HT's will
solve my problem. Thanks for any help!

Find an older cordless phone. Most converted to 10.7MHz, and then again
to 455KHz. Often a Motorola IC to do the IF strip. Older would mean
easier to work with components, ones that can be identified. If you're
lucky, you can extract the circuitry intact, if not just pull the parts
and build on a new board. You'll get all you need, including a crystal to
convert from 10.7MHz to 455KHz.

Baby monitors used this scheme, at least some of them. 49MHz superhet
walkie talkies did too. The cellphones I've taken apart generally go to a
higher IF around 45MHz or so, and then down to 455KHz, so those are out.

Just about any ham FM rig used 10.7 and 455KHz, as did many monitor
receivers and scanners, so find scrapped units and transplant their IF
circuitry.

Michael