[TMC] GPR90-RXD Receiver & SSB

[Roy Morgan]

On Dec 14, 2008, at 12:04 PM, Mark Johnson wrote:

> I recently acquired a GPR90-RXD receiver and did a pretty thorough  
> overhaul and alignment.

Mark,

Good, it probably needed tweaking, but likely no real serious repair.

> ..., I find that using it for SSB or even CW, it is not as good as  
> other receivers I have of similar genre.

Your experience is typical.  Experienced folks I've talked with about  
that receiver don't like it.

> From the experience of others, is this common for this receiver?

Yes.  We can surmise that the reason the company built the GSB-1 SSB  
adapter is because the receiver was not very good without it.  GSB-1's  
are, of course, very hard to find.

> Overall I have to say I'm disappointed with the receiver.

You are not alone.

Here some cute tricks:

Feed it a strong CW signal - way above S-9.  Then with the RF gain  
full up, and the BFO on, tune slowly across zero beat.  See if the BFO  
gets sucked in near zero beat.. that is the BFO oscillator gets  
captured by the changing signal so that true "Zero beat" disappears.   
Verify what's happening by using a weak but definitely hearable signal.

Second:  try switching the audio filter switch (I forget just what the  
positions are marked) and see if you get a lout POP between two  
positions in one direction.

Then, measure the drift after warmup on a moderate frequency, say 14 mc.

Roy
Who wants a TMC RTTY terminal unit.

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073