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

[John Kolb]

Adding a digital display to my HQ-180 made it much more enjoyable to use
as an SWL receiver - for BCB use, the dial should have enough resolution 
as is.

The HQ-180 is a real knob twittler's delight. The 180 is a real pleasure 
to use
when you are fighting hetrodyne or steady carrier QRM. Being able to use 
the notch
filter on the QRM, then use the fine tune control to move the receiver 
passband
around without affecting the notch is really convient. Unfortunately, 
the various
selectivities of the 180 don't have a very good shape factor.

The better shape factor of the 390's, particularly the 390A with it's 
mechanical filters,
makes it usually the winner when fighting adjacent channel crud.

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
<http://jlkolb.cts.com>

Damon Raphael wrote:

> Hello Bob,
> I use a HQ-180, R390 and R390a.
> The 390 radios have more accurate frequency readout, to start. This is 
> not surprising since they cost a fortune in 1950s and 1960s dollars 
> when they were manufactured. They have the best freq readout of 
> probably any non digital radio ever made.
> The 390 and 390a have the ability to listen to "wider" signals which 
> means better audio fidelity when you want to listen to broadcast music.
> What the HQ-180 has, that the 390s don't, is a tunable notch filter.
> I use the Hammarlund mainly for SWL and the 390s for ham radio. The 
> mechanical filters in the 390a are more effective for rejecting 
> interference than the LC filters in the 390, but may give somewhat 
> poorer quality audio fidelity at the same bandpass width.

<snip>