[R-390] R390/Solid State-|

[Michael Young]

I already built the outboard SSB detector.  Two Mech filters I was able to
pickup, 455kc USB and LSB.  So I had simultaneous dual sideband all in a
minibox.  Connected to IF output.  Fast Attack, slow release. Have had that
for 15 yrs.

Direct frequency readout with out requiring band change "messing" is a real
desire.  I think AADE may have something that will work.

mike


----- Original Message -----
From: <DJED1@aol.com>
To: <myoung76@bellsouth.net>; <r-390@mailman.qth.net>
Sent: Friday, August 09, 2002 6:27 PM
Subject: Re: [R-390] R390/Solid State


> Hi Mike- I've been reading the mail, but in the interest of bringing up
your
> ratio of serious replies- I'll offer a few opinions:  I'm also an EE (not
yet
> retired).
> I converted an old Super Pro to solid state back in the 70s.  In that
case,
> the objective was to reduce the drift.  It did OK, but no other
improvement
> that I can recall over the original radio.  I eventually gave  it away,
and
> it was likely scrapped.  As others have noted, this conversions used
> dual-gate FETS, which are harder to find than tubes.
> I've had a low-mileage R-390A for about 25 years, but the thought has
crossed
> my mind about improvements.  Tube life has not been an area to improve, I
> don't think I've replaced more than 4 tubes in 25 years (and I've got
enought
> spares for another 50 years).  So no good reason to change there.
> I thought about improving the frequency readout- it sure is impressive to
set
> my new solid-state receiver to the nearest 10 Hz.  I concluded, however,
that
> 300Hz is good enough for any use I would have, tho I'm still thinking
about
> how to set each band so that you don't have to calibrate each time.  So no
> strong reason there, tho it might be nice.  As one of the other posters
> noted, you can buy or make an external readout for the PTO.  Still needs
to
> be set to each band.
> In terms of sensitivity and strong signal performance, the R-390 can only
be
> equalled by a few commercial solid-state receivers (if you've got $20K for
> one).  so probably a minus for any solid state substitution.
> Same for drift- almost negligible despite the temperature rise because of
the
> tube heat.  Not as good as newer solid-state, but no great need for
> improvement with drift of a few hundred Hz.
> Finally, the greatest weakness is the lack of SSB detector.  Thid really
> needs improvement!  I compromised on this one- I built a solid state
product
> detector and AVC that connects to the radio's IF output, and audio and AVC
> terminals on the back of the radio.  This allow seamless operation of the
> radio in SSB, using all of the front panel controls.  Just a little box on
> top of the radio.  And no holes in the radio, which I assume will fund my
> grandchildren's college education someday.
> The one drawback to the product detector is that I need to manually offset
> the BFO for sideband selection, thus I need to recalibrate when switching
> sidebands.  I'm now working on a new version with some surplus 100 KHz
> filters, which will allow sideband selection without recalibrating.
> Once I get that done, I think it will be close enough to perfect for my
> purposes.
>
> However, if you launch into some work- keep in touch.  I'm still looking
for
> the solution to get the crystal oscillators exactly on frequency.
>