I also thought that QST left out more information than they included. I had
seen the TR7 Renewed article on WB6HFN's web site but did not put the name
together.
I was mostly interested in the DDS VFO that he used. In corresponding with
Marc about it I found out that it was KD1JV's Mini DDS VFO which uses a
AD9835 DDS chip and a Atmel AT90S2313 cpu. I could not find the source code
or hex file for Steve's project. In corresponding with KD1JV he indicated
that the Mini DDS vfo was a project that was done over 10 years ago and had
only sold about 50. Because it was done on his 486 computer the media is
gone and no info on redoing the project and no desire to do so since there
is much better stuff out there. Floyd's use of Craig Johnson, AA0ZZ and I
think AMQrp project IQPro (pc boards sold by Kanga US) would be an excellent
choice for that and Floyd has some information and pictures of his install.
Floyd, K8AC also has modified source code for the TR7 and the IQPro.
My interest in the DDS VFO used for the R7 mod was not for use with my TR7
but because I bought a very low serial number R4B parts chassis on ebay
(from a ham who described it as a R4C). The R4B had no tubes, pto, dial, or
either of the brass shaft/tube for the preselector rack or passband switch
and no bearings for them. So it was just a chassis. I am not a purist and
since I have to do a major overhaul anyway I thought this would be a good
candidate for installing a DDS vfo and digital dial. I had wanted to use
the WB2V/N2APB/AA0ZZ DDS vfo from 1997 QEX (
http://www.njqrp.org/mbrproj/9850dds.html ) which FAR sells a pc board for
and it used a 16F84A but Craig Johnson modified for a 16F628 recently. What
I can not do is program the cpu to have limited coverage (4.9mhz through
5.6mhz) like KD1JV's program did. I tried contacting a couple other vendors
that sell DDS vfo's and none could imagine why I would even want to limit
the range to 500 khz plus overlap! N2APB wants me to use the AMQrp HC908
board and they have an excellent article about it at
http://www.amqrp.org/kits/HC908%20VFO/index.html
and using it for a vfo on their web site. Since George offered to help me
with this I will go with the HC908. If it were not for that I would be
tempted to try the WB6DHW ( http://wb6dhw.com ) AD9912/AD9954 DDS boards.
Another possibility is the AVR Butterfly like WA5BDU has at
http://pages.suddenlink.net/wa5bdu/butterfly_dds.html but am not sure if the
Butterfly board is still available from Atmel or not.
Has anyone else done the DDS VFO (not as an external vfo)? How did that
work out? Has there been enough output or did you have to add a buffer or
amp like
http://pages.suddenlink.net/wa5bdu/dds_amp.htm
in order to get enough output?
Thank you.
Jim Pruitt
WA7DUY
----- Original Message -----
From: "K8AC"
To: "Drakelist"
Sent: Monday, March 16, 2009 3:50 PM
Subject: Re: [Drakelist] Article in April 2009 QST
I think you need an additional opinion on this! First, the QST article is
a very poor condensed version of the DK4DDS (PA1HFO) mods that have been
floating around for a few years now. For some inexplicable reason, many
of his solutions were left completely out of the article (e.g. solution for
power output not flat, and solution for low sensitivity on the higher
bands. ) I don't think it's worth all the work to install all of the mods
shown in the article, but the ones NOT shown are interesting.
I just checked the magazine, and see that they left out the PTO stabilizer
mod as well. That one can be added without extending the cabinet in any
way and is documented on the Web. Personally, I prefered to address that
problem with an outboard DDS VFO which has served me quite well for a
while now.
73, Floyd - K8AC
----- Original Message -----
From: "DW Holtman" To: "Drakelist" Sent: Monday, March 16, 2009 4:51 PM
Subject: [Drakelist] Article in April 2009 QST
Hello,
Did anyone read the article on modernizing a TR-7 by DK4DDS. It has
information on adding a ton of features, such as DSP Noise reduction,
curing the PTO Drift, Notch Filter, Improving the sensevity on the higher
bands, Speech Processor and a bunch of others. It is some great food for
thought, for bringing a great radio into the 21st Century.
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