[R-390] Mech filter REPAIR Lankford Trial?

[ToddRoberts2001 at aol.com]

In a message dated 6/2/2007 12:21:48 PM Eastern Standard Time, 
shoppa_r390a at trailing-edge.com writes:
I was just re-reading Dr Lankford's suggestion yesterday. HSN #30,
pages 2-8. He suggests the Collins "low-cost torsion filters", 
6kc BW #526-8636-010, 2.5kc BW #526-8635-010, and 0.5kc BW #526-8634-10,
along with some misc. chokes, impedance transformers from Mouser,
resistors, etc. to match it all into the existing IF deck circuitry
with some mods to the IF deck itself.
 
 
I can tell you the Collins low-cost Torsion mechanical filters are excellent. 
I have made up some replacement IF filters for the Racal 6790 and the Icom 
R75 using the 6Kc (really 5.5KHz) BW torsion filters and was delighted with the 
results. 
       If there is any interest out there I would consider making up a few 
drop-in replacement 5.5KHz BW mechanical filters for the R-390A. They would be 
mounted in brass tubing the same size and diameter as the originals with a 
mounting flange and feed-thru insulators on the ends.
       Otherwise for the same bandwidths and specs it would be better to 
rebuild the original filters for the R-390A.
       Once someone masters rebuilding the transducer coils the rest is 
relatively easy. For now the best thing the rest of us can do is hang onto any 
'bad' filters you might have - save them for possible rebuild!
       73 Todd WD4NGG



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