[Premium-Rx] WJ-340A manual

[GandalfG8 at aol.com]

In a message dated 21/06/2007 19:59:15 GMT Daylight Time,  
davidatkins50 at f2s.com writes:

Hello to  the list.

I managed to obtain a WJ-340A-6 vlf receiver, and I'm  struggling to make the
best of it. Does anyone know where I can obtain a  manual, handbook,
schematic, or even an info-sheet for this receiver  series?

It seems very sensitive, but there are a couple of items I'd  like to tackle.
It takes up to four hours for the L.O. to settle down. I  run my RA1792 with
an external frequency standard -- even without, it is  rock-solid in
comparison with the 340A. Has anyone tackled this on a 340A?  Is this warm-up
time normal for them?
The tuning is very coarse; even  the "Fine-tune" is too coarse for creeping
up on a beacon signal. Am I  right in thinking WJ used a varicap, here? Would
a multi-turn pot improve  things?
There are some rear-apron sockets that I would like to understand  the uses
of. Can anyone help?
And finally (this time), what is the "log"  position on the mode-switch for?
Hi David
 
I can't help with the manual, but there is a manual for the WJ 357 LF  
receiver in the group archives and I suspect they might be quite similar.
 
This receiver is going to have a capacitor tuned VFO, as with several  
similar sets and tunable demodulators of the same period.
It's a beautiful tuning mechanism, WJ tuning mechanics tend to be  
engineering works of art, but it's never going to match the internal crystal  standard 
of a 1792, let alone anything better.
 
When you refer to it taking four hours to settle down, is that with or  
without the DAFC activated?
DAFC =digital automatic frequency control
 
Without DAFC you are free running the VFO.
The DAFC provides a correction voltage for the fine tuning, which is  very 
likely to be a varicap -- it is on my tunable demodulators anyway, and that  
should lock the final digit to that shown on the DAFC switch position.
This does of course does assume that the VFO is close enough to start with  
to be locked so worth leaving it to settle anyway.
The DAFC control voltage is generated in the counter module and I have one  
demodulator still to be fixed where this voltage is not being generated  
properly so that might be a problem to look out for.
Again the 357 manual should prove useful, for the concept if not in detail,  
as that also uses DAFC.
 
Can't help with the "log" position and the recent Ebay photos of these  
aren't clear enough to read what's marked on the back, but might be able to help  
there if you can tell me the socket markings.
 
regards
 
Nigel
GM8PZR