[ARC5] OK Smart People- FM Demodulator

[Bob Macklin]

Several years ago while testing a Heath Shawnee (50MHz) I found a signal at 
54.1MHz. It turned out to be a local 50MHz repeater. I could monitor it just 
fine using slope detection.

I also did the same thing with my Heath Pawnee (2M) transceiver on the local 
2M repeaters.

You can create FM(actually PM) by amplitude modulating the 8MHz crystal 
oscillator.
Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Tom Dawson" <wb3akd at earthlink.net>
To: "David Stinson" <arc5 at ix.netcom.com>; "ARC-5 List" 
<arc5 at mailman.qth.net>
Sent: Friday, January 18, 2013 7:38 AM
Subject: Re: [ARC5] OK Smart People- FM Demodulator


> Alternate Suggestion (There's always gotta be one)
>
>
>
> NE604AN FM IF/Demod chip.
>
> Still available in reasonable quantities on (gasp) ebay for the 4 dollar 
> range.
>
> The AN suffix means it'll work for IF's up to over 20 Mcs, and I've used 
> in on 21.4 Mcs.
>
> It has two sections, and there's supposed to be a filter bethween them, 
> but with the receiver's existing IF amplification, you probably only need 
> the back end and a coil and condenser for the quadrature detector.
>
>
> just a thought...
>
> 73
>
> Tom
> WB3AKD
>
>
>
> ----- Original Message ----- 
> From: "David Stinson" <arc5 at ix.netcom.com>
> To: "ARC-5 List" <arc5 at mailman.qth.net>
> Sent: Friday, January 18, 2013 7:58 AM
> Subject: [ARC5] OK Smart People- FM Demodulator
>
>
>> Calling all "Smart People:"
>>
>> Doing some research on a "Borg Implant" FM Demodulator
>> in the hopes of breathing life into many dust-gathering VHF sets.
>>
>> I found this interesting circuit:
>>
>> http://jaunty-electronics.com/blog/2012/08/no-tune-ne602-ne612-fm-demodulator/
>>
>> It's supposed to work between 420-500 KC.
>> I'm hoping to "tweak" something like this for 15 MC,
>> since the NE602 / NE612 will work well into UHF.
>> What puzzles me is the tank circuit L1 / C5.
>> 820 uH and 100 pF resonate at 555 KC.
>> Is that right?  And if so, what resonant freq would
>> one use to get the thing to work at 15 MC?
>>
>> 73 DE Dave AB5S
>>
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