[TenTec] SGC's ADSP2 board on a TT Omni VI+

[Bill Tippett <btippett@alum.mit.edu>]

KQ6XY wrote:

Check out page 22 of the latest issue (Sept 2003) of CQ magazine, which
reads:
" With the ADSP2 board installed, the receiver in the Argonaut V has 
finally surpassed the well-respected Ten-Tec Omni VI+ (The Omni VI+ has no 
filtering, which is effective against atmospheric noise, and its automatic 
notch filter reacts too quickly to be useful for CW operation.)..."

        Don't get too excited Larry...this article was written by someone
with ties to SGC as noted in the article's last paragraph.  This review
is typical for CQ Magazine...long on talk and short on facts.  Sorry but
there is NO WAY any audio DSP in an Argo V can make up for its weak
front end compared to an Omni VI+.  Look at ARRL's IMDDR3 and BDR
numbers on Elecraft's summary here:

http://www.elecraft.com/K2_perf.htm#5%20kHz%20numbers

Radio   IMDDR3  Blocking

Omni VI+        86 dB           119 dB
Argo V  62               67

Delta     -24 dB              -52 dB

Sure an ADSP2 might help an Argo V, but it is already deaf to signals
that an Omni VI+ will easily hear.  NO WAY would it enable an Argo V
to surpass an Omni VI+ in strong-signal handling performance.

        If you REALLY want an excellent DSP filter for the Omni VI+, here
is an alternative which I feel will beat the socks off most DSP's currently 
on the market. This is not just my opinion, but the experience
of many EME guys.

1. Buy K6STI's DSP Blaster software for $100. This works only with
a 16-bit Soundblaster ISA card and the version (Vibra16 or CT4170)
which has a 16-bit DAC is the one to use. I bought my card for $1.04
on eBay so this is not a huge investment. To run the program with
full features and not oveload the processor, you need a ~200 MHz
Pentium class computer, although I even got it to work marginally
with an old 486/33. Assuming you already have a suitable computer at
your operating position, the incremental cost is just a little over
$100. If you don't already have a computer, 200 MHz boxes are
selling for <$50 on eBay these days! Here is a brief description of
DSP Blaster:
<http://www.setileague.org/software/dspblast.htm>http://www.setileague.org/software/dspblast.htm 

(Note K6STI's E-mail address has changed so contact me for it if you
are interested.)

2. Coherent CW is a unique capability DSP Blaster provides beyond the
usual filtering features in other DSP's:

"Just a note to let you know that DSP Blaster 2.0 is now available.
It features a new processor for coherent reception of CW signals.
This processor provides a 3-dB S/N gain for phase-stable signals.
You'll find a writeup about it in Stan Horzepa, WA1LOU,'s column in
the October 1997 issue of QST."

K6STI actually measured this 3 dB S/N advantage and I can hear it
with my ears. Coherent CW is NOT in any current internal DSP's to my
knowledge.

3. I run Orion's Aux I/O Audio Out (a fixed level which is
independent of AF Gain settings) to the input of the sound card, and
use a second set of headphones on the output. When I feel I need
additional DSP capability, I simply switch headphones and activate
DSP Blaster on my computer.

        It's been too noisy so far to fully evaluate DSP Blaster on 160,
but I have used it enough listening to weak signals on the higher bands
to cause me to feel it was well worth the $100 incremental cost (which
is about 1/2 of the $180 ADSP2 not counting installation).

73, Bill W4ZV



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