[R-390] The R-390A, a GREAT LF rig!

Fri, 06 Sep 2002 06:22:27 -0700

Hi Phil

I have been away from this list for several years, so i am
curious about your LF converter. Is it classified info :),
or could i find a schematic for this somewhere? I am
currently in process of making a double-tuned LW loop with a
view to doing some LW listening this winter, mainly looking
for Russian Far East stuff (yeah... weird... i know... but i
gotta do *something* to stay sane in the pacific NW during
the "big mud") Was planning to use an R-71 as the receiver,
but it would be cool to use a 390A, with a converter.

thanks for any advice

Bob Bennett, Maple Vly, WA

Philip B Atchley wrote:
> 
> Hello all.
> Well, here we go again, "I'm trying to stir the pot".
> 
> I'm an avid Longwave Beacon chaser (NDB'S).  It's no mean feat to copy a
> 25 watt Longwave beacon at 2000+ miles or a obscure beacon in Brazil at
> 6500+ miles (I've done both).  It does put GREAT demands on both receiver
> and antennas, especially if you live in a 2 by 4 lot in a mobile home
> park with all kinds of computers, dish receivers and other RFI generating
> trash from China.
> 
> Lately I've been using a homebrewed longwave converter with internal low
> pass filter, antenna tuner/40dB pre-amp with a Hallicrafters SX-71A
> receiver.  In times past I've used IF filters as narrow as 125Hz and
> audio filters as narrow as 12.5Hz (modified DSP).  At this game
> selectivity and frequency stability is EVERYTHING (Some NDB's with
> duplicate ID's are within hundreds of Hz or less of each other).
> Unfortunately the Halli does NOT have good frequency resolution, even
> with calibration charts.
> 
> After I put the R-390A in the listening position and used it the past
> couple of nights I figured that it would make a GREAT receiver for my
> purposes, the limiting factor was now my homebrewed LF converter which
> used a NE602 mixer, known for poor dynamic range.
> 
> So, I dug up the Longwave modification for the R-390A, put it on a small
> perf board and stuck it alongside the 1st mixer tube.  I installed a
> solder type BNC jack in place of the IF output jack for the longwave
> antenna.  This entire thing is a no holes drilled, no solder into the set
> modification, and I'm pleased to say it works very, very well.  As it
> couples into the cathode of the first mixer it doesn't appear to affect
> operation above 530kHz at all.
> 
> When I connected my 60 foot loaded sloper antenna (the one I use for
> longwave) to the LF antenna jack I was able to copy many of the daytime
> NDB's, though gain was obviously way down do to no RF amplifier.
> 
> I then modified my Longwave converter, pulling the NE602 out of it's
> socket (good reason for using IC sockets).  I added one more BNC jack to
> the two already on it and connected that to the output of the converters
> pre-amp section (this is a Tunable pre-amp with sharp selectivity
> itself).  The unit was set up top ground the HF antenna jack of the
> R-390A when the pre-amp is on.  This in effect switches the antenna
> between the LF and HF antenna jacks of the receiver when the LF pre-amp
> is turned on.
> 
> Does it work???   I'LL SAY IT DOES!  I have a better signal/noise ratio
> on longwave than I ever had through the converter itself.  The 40dB gain
> of the pre-amp more than makes up for the lack of an RF pre-amp in the
> R-390A on longwave.  Signals are strong and clear.  If the RF gain is
> wide open FCH-344 in Fresno (65 miles) pegs the R-390A RF meter, yet
> there doesn't appear to be any IMD at all (due to the selectivity of the
> pre-amp).  With the converter I used to hear a "ghost" of FCH-344 behind
> MO-367 and a couple other places.  They are no longer there!
> 
> AND, for the "purist" the best part of it is the fact that the
> modification can be removed in about 5 minutes, putting the original IF
> output jack back in and pulling the wire out of the tube socket.
> 
> 73 de Phil  KO6BB
> Loving home provided for wayward Boatanchor Receivers
> [email protected]
> Merced, Central California
> 37.18N  120.29W  CM97sh
> 
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today!  For your FREE software, visit:
> http://dl.www.juno.com/get/web/.
> _______________________________________________
> R-390 mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/r-390