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

[Walter (Volodya) Salmaniw]

At 03:23 PM 2/17/2005, ToddRoberts2001 at aol.com wrote:
>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

Guy Atkins recently did the roofing filter thing with his 6790 which vastly 
improved it's performance.  This rig was also recently sold on 
eBay.  Perhaps Guy can make some comments on the improvement in 
performance.......Walt.