RX320 (fwd)

Frank Gentges gentges@itd.nrl.navy.mil
Sat, 11 Sep 1999 15:35:51 +0000 (GMT)

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The following message was sent to the TenTec rep I spoke to at Dayton.  I 
did not attach the files I sent to Gary to reduce the message size on 
Frank K0BRA

---------- Forwarded message ----------
Date: Sat, 11 Sep 1999 15:33:14 +0000 (GMT)
From: Frank Gentges <gentges@itd.nrl.navy.mil>
To: ditsnbits@tentec.com
Subject: RX320


I talked to you at the Dayton Hamvention.  I'm sure you had a whole lot of
people come by so I will fill you in on the whole story from the start and
also bring you up to date. 

I and several others at the Amateur Radio Research and Development
Corporation (AMRAD) have been working to develop techniques for the Low
Frequencies (LF).  AMRAD is an amateur radio club operating as a non-profit
corporation.  We are a bunch of technical guys who like to work on more
technical things than many hams would be interested in.  We have a number of
accomplishments over the years to our credit that include the original packet
radio specification and the ARRL Spread Spectrum handbook.  We took the
initiative to get an experimental license from the FCC to operate on LF. 

ARRL has petitioned the FCC for LF allocations for radio amateurs and no
serious objections have been raised.  In the absence of serious opposition it
looks like this may be approved within the foreseable future.  If approved,
there will be a market for good LF receivers. 

As part of my work on LF I modified an RX320 to make it work at full
performance on LF.  My modification was published in the AMRAD newsletter. 
Since then ARRL has asked my permission to publish the article in their new
webzine. They have not indicated w hen it will be put in/on the web.  It does
look like the access will be limited to ARRL members.  It is new so all the
details may not have been fully defined yet. 

I have attached this article and two pictures for your information.  A note
was put on one of the internet news groups about my article and I had about 6
inqueries resulting from it.  I do note that some comments on the internet
say the RX320 performance below 2 mhZ is reduced and therefore it may not be
the best receiver for MF DXing.  These comments seem a bit strong to me in
any case and with the modification have no merit. 

This modification continues the RX320 performance all the way down to 10 kHz
with no immediately obvious degradation.  As noted in the article we measured
a slight improvement at 30 mHz.  We did not verify the 3rd order intercept
point after the modification and at some point that test should be done. 

At AMRAD we have an interest in improving the RX320 beyond this modification. 
We are looking at an improved PC/RX320 interface that would include DSP
processing within the PC along with enhanced PC graphics.  This approach
would leave the RX320 firmware as is.  Unfortunatly we believe that without
firmware changes this will establish limits on weak signals that we cannot

Enough interest in working on the firmware has developed to the point that I
and other members now have 3 Analog Devices EZ DSP kits and an Analog Devices
In Circuit Emulator (ICE) package.  Two of us also have purchased Aerospace
Software's ADSP 21XX software package which looks to be a valuable approach
for assembly language development.  We think we have accumulated a
comprehensive and powerful set of tools to begin development on weak signal
code for the ADSP 2100 and the RX320. 

Members expect to begin work on code for the ADSP 2100 DSP that would be used
to replace the RX320 firmware with new code more oriented to LF weak signal
work.  The ADSP 2100 has some tremendous narrow band processing capability
beyond that now available in the RX320. If this capability can be expoloited
it could gain 10s of dBs of processing gain on very weak signals.  We see
this new code contributing to HF performance as well. 

Our work would be simplified if we could have access to the RX320 source
code.  The best option would be "open source" DSP code much as TenTec has
done with on the RX320 interface specification.  We have all see the value of
TenTec's vision of releasing t his interface specification with the emergence
of several excellent RX320/PC interface programs on the internet.  As a next
step in that vision, we would like to see open source on the RX320 DSP code. 

I ask you to explore how we might accomplish this.  Given our non-profit
status I can assure you that we have no intention of competing with TenTec. 
Rather we see our work as adding to the value of your product with a wider
audience than just the SWLs.  We envision that a properly groomed RX320 can
become a record breaker capable of being a part of the first Transatlantic LF
QSO.  We would like to work on making TenTec and their advanced receiver
concepts a part of the first Transatlantic amateur LF QSO. 

We also feel the RX320 with open source DSP code has the potential of
becoming an important DSP educational tool. It could be used to teach "total
system" use and understanding of embeded DSP applications that mix complex
signal processing along with simp le system control.  With the demand for
more DSP engineers and the schooling needed open source DSP code could create
an important new market for your hardware and our firmware work. 

We believe that by releasing the DSP source code to open source TenTec has an
opportunity to leverage this into significant gains in an already popular
product for minimal investment in money and people. 

Frank Gentges K0BRA