[Premium-Rx] 590H Filters?

[John Reed]

John Reed here.

I'm a member of this group and have been watching this topic for the past 
few days.  I built this board quite a few years ago, and it's still 
performing well.  My idea was to take the control of the filters away from 
the microprocessor since it wouldn't do what I wanted.  It's not difficult 
to do this.  I just added a rotary switch on the front panel in place of the 
squelch control and let that control the relays that I use on the board to 
switch the filters.  There were a few other components needed on the board, 
and I still have the notes if there are questions.  On the Harris, the 
addition of the post IF board made little difference except for very narrow 
bandwidths, less than 100 Hz.  On my Racal (RA6793A) it made a big 
difference, even on 1 KHz filters.  By the way, I've compared both these 
receivers and I like the RF-590 better.  The only place where the Racal 
beats the Harris is when I want to receive a weak signal close to a strong 
one.  Otherwise, the Harris is a lot quieter.  There seems to be a lot of 
microprocessor noise in the Racal.

John Reed, KA5QEP


----- Original Message ----- 
From: <ToddRoberts2001 at aol.com>
To: <cntaty at wcc.net>; <premium-rx at mailman.qth.net>
Sent: Tuesday, January 06, 2009 10:05 PM
Subject: Re: [Premium-Rx] 590H Filters?


>
> In a message dated 1/6/2009 7:55:51 P.M.  Eastern Standard Time,
> _cntaty at wcc.net_ (mailto:cntaty at wcc.net)   writes:
> To all:
>
> I have tried to get information about the 590H from Harris...nada!!   They
> won't even talk about it and will not give you any hints.  I have  two of 
> the
> items and they are good receivers except for this "painus in the  a_us." 
> The
> unit was designed for frequency hopping service and its  reputation 
> indicates
> it is well designed for this and most other services: it  is also much
> heavier than the 6790 RACAL series.  Frankly, I prefer  RACALs over the
> Harris but some people like Chevys and some like Fords.   I worked at 
> Collins
> (Dallas) way back in the Sixties and during that time  made friends with 
> many
> people in the industry...some still at Harris and  neither I nor any of my
> friends from that period have been successful with  Harris (collectively) 
> in
> getting the necessary information that would a allow  a modification of 
> the
> receiver such that it will perform as Todd's  acquaintance's.
>
> Frankly that is not a bad way to proceed and If Todd could come by  the
> information in a more graphic form, I, for one, would give it a  try...it
> doesn't seem too hard at first blush!
>
> Bill
> W5STP
> _______________________________________________________________
>
> Hi Bill,
> John Reed KA5QEP is  the one who built his own IF boards for his RF-590.
> Actually he built two boards  - a Pre-IF board with set of filters and a 
> Post-IF
> board with another set of  filters. He found that he was able to improve 
> the
> S/N ratio of very weak signals  in the narrower bandwidths by cascading 
> two
> narrow filters in series. He found  the improvement wasn't too much in the 
> wider
> bandwidths so he concentrated on  cascading  narrow cw filters.
> A few years ago he sent me a collection of notes on his homemade IF boards
> with  schematics. I made pdf copies of them and would be glad to email you
> copies of  them if you are interested. I was planning to make up my own 
> custom
> RF-590H IF  board someday and it is one of those projects I haven't gotten 
> around
> to yet.  John's notes should be enough to show someone how to do it. 
> Someone
> could make  just one IF board if they didn't want to fool with having to 
> use
> two in series  if they didn't really need to cascade  filters.
> I haven't corresponded  with John Reed in about a year. I am sure he would 
> be
> glad to help with any  advice or info he still has.  Here is his last 
> email
> address of a year  ago:
>
> _jreed at alum.mit.edu_ (mailto:jreed at alum.mit.edu)
>
> 73 - Todd WD4NGG
>
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