[Collins] KWS-1 Upper/lower sideband supression

[Dr. Gerald N. Johnson]

Carrier suppression comes from the balanced modulator balance, 
capacitive and resistive.

Opposite side band rejection comes from the filter. What audio frequency 
are you using to measure the side band rejection, 1 kHz is much better 
than 100 Hz? Are the carrier frequencies on the slopes of the SSB 
filter? You may have to sweep (manually with signal generator or LF 
sweep generator) the filter response and check the carrier frequencies 
with a counter. Filters that old have been known to go bad as have 
crystals. Y101 and Y102. There are some capacitors in the carrier 
oscillator circuit that could also have moved the crystals into the 
filter pass band. Three things are critical. The carrier frequencies 
should be set to about the 30 dB down point on the slope of the filter, 
on opposite sides of the passband, and the filter must have the 
predicted passband about 2.5 kHz wide with steep skirts. The sideband 
suppression is dependent on those.

it sounds to me as if the filter is the primary problem. Its not longer 
as selective as needed.

On 7/5/2014 1:14 PM, Bill Riches wrote:
> Just noticed that upper/lower sideband suppression is only about -15 db.
> Specs are -50 db.  Carrier suppression is about -55 db.  Any suggestions?
> 73,
>
> Bill, WA2DVU
>
> Cape May, NJ
>
73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association