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

[Alan Victor]

If any interest prior to the land fill or other Earth friendly paths.
.
I have an excellent copy from microfiche from the Rome Air Force
Development Center

*Preferred-circuit Techniques for Receiver Applications*
Over 1000 pages Tech report no. RADC-TR-67-216.
Date June 1967.

Covers every conceivable circuit technique at the time for wideband
receiver techniques; 1 MHz-10 GHz.

Any interest, email me direct. 73' Alan

On Sat, Jan 6, 2018 at 7:16 PM, Tisha Hayes <tisha.hayes at gmail.com> wrote:

> 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.
>
> -----------------------
> 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.
>
> -----------------------
> 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.*
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