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

[Carcia, Francis A HS]

I also added post IF filters in my RA6830. This is an excellent modification
and there is enough extra gain
after the 757 amp that no additional gain was required to maintain the MDS.
A little harder in the 6790 because you have to open up the coupling cap and
add cables. fc

-----Original Message-----
From: ToddRoberts2001 at aol.com [mailto:ToddRoberts2001 at aol.com]
Sent: Thursday, February 17, 2005 6:23 PM
To: premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] RE: Mods for Racal 6790GM


I forgot to mention that John Reed KA5QEP has done some very good research 
into adding a post I.F. filter board to the Racal 6790 as well as other 
receivers like the RF-590. This involves adding a buffer amp to the output
of the 
original I.F. board and running the output to a second board with a few
switchable 
narrow I.F. filters - in effect cascading a second I.F. filter to the first.

He said this gave an outstanding improvement in weak-signal readability when

switching to narrow filters for weak-signal cw work. He also recommends
adding 
an 8KHz wide Roofing filter to the 6790 - that is about the bandwidth of the

roofing filter in the RA-6790 VLF version 2nd mixer I believe. It limits the

bandwidth to about 8KHz but the original 16-20KHz wide filters in the 6790's

I.F. are probably not used that much in most normal mw and shortwave
listening. - 
Todd Roberts WD4NGG

_______________________________________________

Premium-Rx Mailing List
To Post: premium-rx at ml.skirrow.org
For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx
Visit the Website: http://kahuna.sdsu.edu/~mechtron/PremRxPage/