[Premium-Rx] Synchronous Detector for WJ and Harris receivers

[jan at skirrow.org]

Hi Craig ....

I built a detector for my R390A radios that might do the trick. It is 
probably more complicated than needed, but I'd tried a variety of 
approaches and was not impressed with the stability or ease of use. My 
design features a PLL stabilized xtal oscillator configured to allow a 
toggle switch to select  USB or LSB. Another switch selects AM or SSB. It 
requires an external audio amp.

As it is currently configured it requires a 455kHz IF input with a level 
more or less what the R390A provides on the rear panel. It outputs an audio 
signal that matches the R390A audio strip level. A trimmer on the pcb 
allows this level to be adjusted so that there is no major level change 
when switching between SSB and AM. The thing connects in place of the diode 
load jumper on the rear terminal strip. For SSB it is in the circuit, for 
AM it is bypassed so that the radio operates as it was originally 
configured. It should be possible to adapt the thing for other radios. It 
does not do anything about the AGC - this is a followup project (for the 
R390A only) that I haven't gotten to. I also have a second design built for 
the 500kHz IF found on some older Collins gear. It hasn't progressed past 
the breadboard stage.

My detector uses an older Motorola MC1496 chip that has recently come back 
into production. My intent was (and is) to make the detector available as a 
bare board, or as a parts kit - but I've been procrastinating at getting 
the final silk-screened pcbs produced. I'm not in the biz of doing this 
kind of thing, but so much work has gone into the prototypes that I thought 
I should share it! The real barrier has been writing up some instructions, 
as assembly is definitely required.

If you're interested I'd gladly share the circuit with you, or provide more 
info on the kits. Please reply OFF LIST.

73s, Jan


At 12:21 PM 12/8/04, you wrote:
>Content-Class: urn:content-classes:message
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>
>I am looking for a good design for a 455KHz Synchronous Detector for my 
>WJ-8718 and Harris RF-590A.  I have seen several good articles in the past 
>but they all use chips like the MC13022 or Exar that are discontinued and 
>not readily available.  Rather than spend $600 bucks on a SE-3 I would 
>like to role my own.  Any ideas?
>
>W9CLA
>Craig L. Anderson, Ed.S.
>Vice President - Administration
>Saint Paul College
>Minnesota State Colleges & Universities System
>651-846-1365 Voice
>651-846-1675 Fax
>
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