[Collins] R388 51j-3

[Dr. Gerald N. Johnson, electrical engineer]

Its not the crystal filter, its the IF transformers that can be stagger
tuned. The crystal filter only allows for a notch or narrow passband for
CW. The phase response of the IF transformers can be significantly
better than the Collins mechanical filters of that era.

Other than the first IF stage on the filter module instead of the
chassis, the J-3 and J-4 are identical everywhere else and with the same
quality in all the front end tubes should have the same practical HF
sensitivity. The sensitivity should be set by the mixers before the IF
(and those are fairly noisy mixer tubes).

But the mechanical filters in the R-390A were cheaper than the IF
transformers and keeping them properly aligned in the R-390.

I've felt the 390 would be a nicer sounding receiver than the 390A also. 

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.