[R-390] R-390A and the SP-600

[Tisha Hayes]

I have had a chance to compare "a few" receivers. Presently I own;

R-390A (three of them so there is some general opinions)
R-390
R-392
SP-200
HQ-129
SP-600 (JX17)
RF-590A (Harris)
R-3030 (Cubic)
CDR-3250 (Cubic)
RA-6790 (Racal, four of them)
WJ-8718 (Watkins Johnson)
5650 (Telefunken, three of them)

- It may seem like "a bunch" of radios but that is just the premium stuff.
I have a tendency to chase after perfection. (it may seem weird but I am
for-real, ask Perry, he knows me personally). Here is my opinion on the
Hammarlund family in comparison to the R-390A;

The SP-600 was a fantastic radio that came out when AM and CW were king
around 1951. The design is reminiscent of the pinnacle of "knob turner"
radios and is a pleasure to use for SWL or BCB-DX listening. The JX17 is
really not the "best model" of the receiver, it was designed to support
diversity pairing with another radio and some changes in the circuitry and
voltages were made. If the crystal filter is close to the IF frequency it
can be a decent radio but often the crystals have changed frequency or the
radio was mis-tuned somewhere along the line. It also has a big problem
with BBOD (black beauty of death) oil caps and the electrolytic (the cans
and the bathtubs) capacitors.

I have tried a bunch of things on an SP-600. Taking B+ ripple down to the
single millivolt level with filtering changes, building the "Nuvistor first
RF" plug-in instead of a 6BA6 and fighting (the never ending) battle
against drive slippage between the frequency disk and the knob

The SP-600 is "drifty" for the first few hours and it is definitely not
frequency stabilized but if you leave it on for a long night of listening
to SWL it is a pleasing radio to listen to. The sound is very full and
sometimes I just listen to AM-BCB at night for the background noise while
doing something else in the house. As has been said it is a pretty
"intuitive" radio except for the IF bandwidth that can be a little
confusing unless you read up on it first.

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The R-390A is almost a generation newer than the SP-600 and is meant to get
on a frequency and stay there. Probably more than a few people on this list
spent their times wearing green or tan, wearing boots and eating K-rations
while they maintained racks full of R-390's in RTTY service. It works great
for data, is not as deaf as the SP-600 at higher frequencies and can be
passably good with SSB with an external converter.

The R-390A is not a knob spinner (we all know that) and I invested
significant time in to smoothing out the drive mechanisms, playing with
synthetic oils and tungsten disulphide to make it less straining on the
wrists. It has a better tube line-up in the RF deck and the advantages (and
disadvantages) of mechanical IF filters. I have added roofing filters
between the RF and the IF and rather than butchering the audio deck I just
pick off the audio and feed it in to the AUX input on a Telefunken 5650
receiver (fantastic audio quality).

By itself the R-390A can be "tiring" to listen to all evening long. It has
a hard to describe "robotic" sound. One receiver does not have that effect
but it is a rare R-390A variant with ceramic filters in the IF.

How I wish the R-390A had an SSB mode.. it might be another reason from
keeping me away from the Harris RF-590A that I have been increasingly using
for dial hunting to listen to the chatter on the geritol-net on 80 meters.

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In the past six months or so I have been buried in Telefunken rebuilds and
while I read the postings on this list I do not contribute as much as in
the past.

*Ms. Tisha Hayes*
*AA4HA*

*Sr. Engineer, 4RF USA.*