[Premium-Rx] RE: Mods for Racal 6790GM

[ToddRoberts2001 at aol.com]

In a message dated 2/17/2005 3:24:36 PM Eastern Standard Time, 
danseven at sasktel.net writes:
Hello Everyone:

I am interested to know if there are any documented mods available to
improve the performance of the Ra6790GM.
For instance, has anyone tried a preselector with this unit, or outboard
preamp?
Any help would be appreciated. 

Thanks, Dan Seven

Hello Dan, Racal did make an RF preamplifier/LPF module A1 that was installed 
in some models of the RA6790 to improve sensitivity. I believe the A1 RF 
preamp was standard issue on the British version RA1792 and can be transplanted to 
the 6790.  Racal also made a special VLF tuning version of the 6790 that had 
a special first and second mixer plus modifications to the LO for more drive 
to the first mixer. This gave full sensitivity of the 6790 down to 10 KHz. I am 
sure you know that new software IC's are available that you can plug into the 
microprocessor board and these extend the tuning range of a standard 6790 
down to 0 KHz. Another area for improvement/modifications is the I.F. board. The 
plug-in crystal filters are easy to mix and match and it is not too hard to 
make up  your own adapter boards to try out different bandwidths in the 6790. I 
have never tried using a preselector and not sure what kind of improvement one 
would bring but would be worth a try. Yours truly, Todd Roberts WD4NGG