[R-390] R-390 AProduct Detector

[Keith Densmore]

Hi Mark,
I just got a letter from one of the list members (VE3EOS)  requesting that
you post the info on the Softrock onto the list (I believe he thinks I have
it).
I use a HP 3586 Selective Level meter and  feed its last IF directly to a
soundcard using free SD Radio software. Spectral Display, infinite choice of
filters and lots of modes including ECSS are a couple of the advantages.
But for the good old '390 I think I'd be satisfied with a 6BE6 product
detector and maybe an AGC improvement.

73,
Keith

----- Original Message -----
From: Mark Huss <mhuss1 at bellatlantic.net>
To: Keith Densmore <densmore at idirect.com>
Cc: <r-390 at mailman.qth.net>
Sent: Thursday, March 22, 2007 7:10 AM
Subject: Re: [R-390] R-390 AProduct Detector


There are several available, depending on how much modification you want
to do. The limitation of the R-390 and R-390A for high-quality SSB
reception are in two areas. First is that the BFO injection level is too
low. The second is that the AGC is not optimized for SSB. Paul Lee was
probably the first to address this. It involves adding a switch,
replacing a tube, and some extensive wiring.

The second, and probably most popular is the ‘Lankford’ mod. Developed
incrementally by several people, it does not involve extensive
re-wiring, and addresses both the BFO Injection issue and the AGC issue.

A third one is a little black-box unit that a few R-390A's were fitted
with. The wiring is unknown to me (anybody out there know?), but it
fitted behind the front panel, and provided fixed BFO and, possibility a
detector and AGC.

A forth one is to add a separate SSB detector/BFO at the IF Out. Several
Mil-Surplus detectors do this, as well as the Hammarlund HC-10. The
latter has the advantage of providing notch filters and bandwidth
filters, though it is expensive at about $300.

The latter option just got a lot cheaper if you have access to a
reasonably fast PC. A lot of Hams are playing with a little device
called a SoftRock. What this is is a IQ mixer/Detector that feeds a
wideband (96 kHz) signal to your sound card. Designed originally as a
direct conversion receiver for the HAM bands, several have experimented
with it as an IF detector. At about $20 per kit (and there is one
designed for 455 kHz), you can connect it to either the IF Input, or the
back panel IF Output through an attenuator. The result is a detector
that with the help of your PC will do AM, CW, USB, LSB, ISB, FM, and
about a thousand filter combinations, including notching. Add a diode
and buffer circuit, and you can generate AVC to feed the R-390.

I have documentation for all the above.

Keith Densmore wrote:
> Hello All,
> Now that I have the PTO aligned and stable its time for the next round.
Does anyone know of a 'known to work' schematic for an R-390A product
detector? Either something solid state, something that uses a 6BE6 or one
that uses the ballast tube socket would all be interesting to consider.
> Thanks All, 73,
> Keith, ve3ts
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