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

[ToddRoberts2001 at aol.com]

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