[Collins] 75A4 and SB 610

[Stuart Martin]

Dave,

The science of using the SB-610 for "true" receiver signal analysis was
documented by H.M. Goosier, W6VFR, in Ham Radio Magazine, March 1972, pg.
36. In his "Monitoring SSB Signals" article, W6VFR describes how the 75A-4
and 75S- series, using the AM bandwidth, allows full wide-bandwidth signal
analysis. It's similar to what I did in the Navy with R-390A's, only the
monitor scope was a bit more sophisticated.

Stu, k2qde


-----Original Message-----
From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On Behalf Of k6xyz
Sent: Monday, June 11, 2007 7:21 PM
To: collins at mailman.qth.net
Subject: RE: [Collins] 75A4 and SB 610

A 5pf maroon mica is what I use....works great.

Regards

Dave Harmon
CCA 97-535
K6XYZ[at]sbcglobal[dot]net
Sperry, Ok.

-----Original Message-----
From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On Behalf Of Dr. Gerald N. Johnson
Sent: Monday, June 11, 2007 6:00 PM
To: collins at mailman.qth.net
Subject: Re: [Collins] 75A4 and SB 610

On Mon, 2007-06-11 at 12:33 -0700, w6om at cox.net wrote:
> I have a beautiful 75A4 and a beautiful Heathkit SB 610 monitor scope 
> with
a 455 KC IF. Looking at the 75A4 schematic it would appear that it is would
be simple to connect the scope to the grid of one of the 455 KC IF tubes
through a small capacitor so it does not load down the receiver IF strip.
> Anyone with an "A4" ever accomplished this, if so which grid did you
couple the SB 610 to and what formula did you use choosing the coupling
capacitor value.
> All the Best
> --
> Ron Weaver - W6OM

The proper place to connect is the plate of the second mixer. Any place
downstream is after the selectivity and tells little about the incoming
signal because the mechanical filter cleans up bad signals.

Usually a few PF is all it takes, the monitor scope has good sensitivity.
--
73, Jerry, K0CQ, Technical Advisor to the CRA All content copyright Dr.
Gerald N. Johnson, electrical engineer

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