[R-390] The best

[Todd, KA1KAQ]

On Sat, Jan 6, 2018 at 9:30 PM, Cecil Acuff <chacuff at cableone.net> wrote:

> Many R-390 series receiver owners also own and use an SP-600 variant. I’ve
> heard the SP-600 is great for cruising the bands and when something of
> interest is found, dialed up on the R-390 to listen.
>

That's how I ran my station for many years. Had the R-390A at the top of
the rack, R-390 beneath that, SP-600 beneath that. The intention was to
surf around with the 600 to locate a weak signal, then use either of the
other rigs to tune it in and listen long-term. Only problem was, more often
than not I ended up just listening to the SP-600. Audio was as good or
better than either of the other two even with the lightweight/overworked
6AQ5 audio stage. Seems I ended up being too busy to search out weak
signals and would tune in a shortwave BC station and listen while working
around the station.

Today the two 390 variants are in their own cabinets, with the R-390 stored
under the basement stairs awaiting space. Found an original cabinet for the
SP-600 at NEAR-Fest a few years back for a whopping $25, it's sitting on a
shelf in the basement also awaiting a place to go here at the new location.
Only the 390A is out and usable at the moment.


> Les will tell you...we just can’t seem to get the job done with just one
> receiver and there is great joy in owning several examples of the available
> technology of the period.
>

He's absolutely right. I suppose if you were severely limited for space, it
would be hard to go wrong with just the R-390A. After all, you can pluck
off the audio at the rear diode load connections to drive a small audio amp
to have decent audio as well. Add a crank to the tuning knob and off you
go. Not perfection, but not a bad compromise at all with the most important
benefits included.

Les is a wealth of information on these old receivers, having owned most if
not all types, including many newer sets. A story I've told here and
elsewhere more than a few times, he's the one who clued me into the
so-called 'drift' issues with the SP-600. While it's true that the earlier
Super Pros (SP-10, -100, -200) took a while to stabilize (clearly stated in
the manual), The postwar -400 was better and the -600, better still. My
first 600 was all over the place and I remember chiming in on here about
the 'notorious SP-600 drift'. Les sent me a private email and asked "Have
you checked the taps on the power transformer?" to which I replied
something like "Huh? Taps?". Once it was out of the rack and on the bench,
I remembered seeing this before but having not owned one, never checked for
myself. Sure enough - a quick check of my line voltage showed the tap is
was set to (120V?) was bumping up against local line voltage. When it
varied, the receiver drifted. That meant, refrigerator, furnace, light
switch, anything, sent it off frequency. Moved it up to the next tap (130V
I think) and voila - zero noticeable drift after maybe 15-20 minutes warm
up time. Even on SSB or CW, it was negligible.


> I also own a couple high end modern receivers as well...nice for
> comparison and great fun to use too. I only listen to AM on my boat anchors
> mostly...when I want to listen to SSB or CW I have better tools for that.
>

Same for me. It's tough to beat the warm sound of a tube receiver pushing
an AM signal into a large speaker. I actually have a pair of RF-590s racked
up with a 1 KW Harris transmitter system in a dual rack set up, about 1K
pounds. Had occasion to use it in a previous life. Very versatile and
stable, but sterile-sounding. When it was pulled from service a few years
back and slated for the scrapper, it instead ended up being surplussed to
storage by the former head of dept and a co-worker until I could work out
picking it up(was down in NC at the time). It's currently living with a
friend in MD awaiting a lift gate truck and warmer WX. Though it still
'works', I suspect from the codes the receivers are tossing out that the
tantalum caps are rapidly approaching crap out mode. Pretty cool receivers,
but apples and oranges when comparing them to something like the R-390. And
as Pete said - the tube gear will still be running loooooong after the sand
state stuff is recycled. Along with actual hardware problems, firmware will
be a big issue. The R-390's firmware is mounted on the front panel. They're
called 'handles'.


> Boomer...great post too...
>

TNX, Cecil. Every now and then I wake up and mumble something into the
keyboard before getting distracted or falling back asleep. Les has photos
of my #1 distraction, now 5 years old. She loves the old radios, especially
the early regens/TRFs, pre-war shortwave receivers and battery sets from
the 20s. All the big transmitters are stacked against the garage back wall
since mid-2016 and 90% of the other gear is still stored in the basement.
One of these days......

de Todd/'Boomer',  KA1KAQ/4