[Hallicrafters] SX-117

[Langston, Mike]

Hello everyone,

 

I have been enjoying my SX-117 for the past few months while working on
other BA's. I monitor AM around 3885 in the evenings and have noticed
something I consider to be abnormal. First, let me say this rig has been
recapped and recently aligned per the manual (all tubes checked of
course). Here's the symptoms:

 

With the bfo adjusted properly, I can tune an AM signal to zero beat in
either USB or LSB with the filter set at 5 or 2.5 KC and the readout on
the dial is right on the frequency advertised by the station
transmitting (this is after a nearby calibration check with the xtal
calibrator which has also been zeroed with WWV). When I switch back to
AM, I have to tune lower in frequency by about 2 KC to peak the signal
on the s-meter and the signal is also "stronger to the ear". If I switch
back to USB or LSB at that point, of course I can hear the carrier (no
longer zero beat). 

 

Is there some reason the AM detector would cause the strongest AM signal
to be approx. 2 KC below the carrier frequency (as established by
zero-beat using the product detector)?

 

The rig works great except for this one "difugilty". All
comments/suggestions greatly appreciated.

 

Mike Langston KL7CD

Dallas/ Ft. Worth



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