[R-390] What is the difference between 390 and 390A

[Roy Morgan]

At 12:46 AM 4/12/2005, you wrote:

>There's been an article or two on adding mechanical filters to the 180. 
>Available, I believe, from the National Radio Club reprint service.

John,

I can't remember the low IF frequency in the 180 - is it 60 kc?. I have an 
HQ-170A on the bench right now.  I'm reminded of the filters used in 
telephone/teletype mulitplex systems since the 1930's.  I have a couple of 
the filters used, one is at 80 kc I think (the ARC-5 low band receiver uses 
80 kc IF, I think.)

In any case, finding such a band filter for the right frequency might well 
get you a voice band width filter of superb performance.

At the NRC publications-reprints page,
http://www.nrcdxas.org/
I find the following:

"R2 SINGLE SIDEBAND RECEPTION ON THE BCB WITH MECHANICAL FILTERS. G. P. 
Nelson. Few commercial receivers covering the MW band have adequate 
selectivity to cope with MW interference--particularly in the presence of 
powerful local stations. Explains how to add mechanical filters to an 
existing receiver for the ultimate in adjacent channel rejection. ( 21) "

"R31 THE SUPER HQ-180. Dallas Lankford. Add a Collins mechanical filter to 
your "180". While not a "how-to" article, problems and results are 
discussed. (4)

"R43 CERAMIC FILTERS. Marc Bergman. A listing and description of the most 
commonly available ceramic filters, with data from tests. (9) "

"R46 SURPLUS MECHANICAL FILTERS. Marc Bergman. Test results of several 
reasonably-priced and available mechanical filters. (3) "

"R67 R390A KHZ FILTERS FOR THE HQ-180. Dallas Lankford. How to use Collins 
DB filters in your HQ-180 receiver. (2) "


Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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