On Wed, 28 Jan 2015, Dave Platt wrote:


In article ,
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.

There was a pretty simple circuit shown in the old ARRL VHF Manual.
I'll see if I can pull out copy and scan it.


Except they don't give much output at 10.7MHz, a pulse counting circuit
would be simple. Those seemed to get a lot of travel for novelty forty
years ago. They'd use logic ICs to amplify and limit the IF signal, then
a divider to get it down to a lower frequency where the pulse counting
could happen (the logic being kind of slow back then so it didn't work
well at 10.7MHz). Put it through a 10.7MHz ceramic filter from an FM
broadcast band receiver to limit bandwidth, mix it down to a lower
frequency (if the amplification and limiting is at 10.7MHz, a digital
mixer would work) then the pulse counting detector. Not unlike that
classic FM broadcast receiver in the GE Transistor Manual, a tunnel diode
mixer/oscillator and an untuned IF strip around 200KHz, then a pulse
counting detector. The concept is like those analog "frequency counters"
that were in the magazines at one point.

Michael