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DSP's (was Re: OMNI VII)

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Subject: DSP's (was Re: OMNI VII)
From: dcalvin@austin.ibm.com (Duane Calvin)
Date: Sat, 01 Feb 1997 00:01:43 +0000
OK, the moderator can feel free to purge this one, and let's not
overstay our welcome.  I've done considerable experimentation with audio
DSP's.  That includes owning two, a Timewave DSP-9 (started as first
available version, updated through ver 3.0 software), and now the JPS
NIR-12.  I have done presentations and demo's of DSP at several area DX
club and ARC meetings.  Six months ago I evaluated my DSP-9 against the
DSP-59+ and the NIR-12 and was so favorably impressed that I purchased
the NIR-12 shortly after.  About two months ago three of us in the area
pooled my NIR-12, a new Timewave DSP-599ZX and an old W9GR kit unit just
to compare their relative performance.  The NIR-12 outpaced both the
others in its ability to pull signals out of noise.  And that was only
using one of its processors, completely ignoring the NIR mode.  The
599ZX was much improved over the DSP-9, 9+, and 59+ which have some
distortion on SSB signals when noise is heavy.  The latest version of
firmware for the 9 was an improvement for SSB, but lost some of the
ability to pull weak signals out of heavy noise on CW.  (I recommend
version 2.x for CW ops, and ver 3 for SSB ops.)  For other measurements,
the 599ZX and NIR-12 were about neck and neck, with NIR left turned
off.  With NIR on, the NIR-12 pulled away.  But, and this is a big BUT,
using NIR introduces a noticeable time lag (125 ms if I remember
correctly) which you may find objectionable on SSB, but would certainly
find objectionable on QSK CW.  (If you monitor your transmitted signal
in either mode, you'll want to use the NIR's switching circuitry to
switch it out when the PTT line goes active or disable the monitored
        The DSP-599ZX has numerous additional functions (modem, etc.) and the
ability to translate a CW tone up or down in frequency which may be of
interest to some ops.  For me, I'm just interested in the basic DSP
functions of noise/interference reduction.  The 599zx is very small,
which makes the operator's controls also very small.  With my big hands,
I prefer the NIR's controls.  I don't need to know that my upper
passband is set for 534 Hz, so the range markings silk screened on the
front of the NIR are sufficient for me (some may prefer the LCD readout
of the 599ZX.)  I shouldn't ignore the old W9GR here.  In random noise
reduction it was almost as good as the other two.  The price you pay on
it is the poor controls.  Selecting a filter is not as easy as pushing a
button but rather a ritual of throwing a switch to start a counter,
watching a bar LED and pushing another button when it reaches the bar
segment that is the filter you want.  Ugh!  It also cannot process
multiple filters at once (noise plus heterodyne elimination plus
passband filtering is not possible simultaneously).  But, its cost is
considerably less than the other two. 
        So, for my money, I would buy the NIR-12 again.  I have never tried the
NIR-10, but I know someone who had one and now has the 12.  He was not
happy with the 10, but is very pleased with the 12.  The DSP-9(+) is a
very nice entry level unit, or you can get started with the W9GR kit (or
scratch build it from the QST article.)  The 599ZX is also very nice,
especially if you need or like some of its additional features.  
        I've not done this information much justice - I hope it is useful to
someone.  DSP's are an emotional topic, sometimes, and I was a skeptic
who was determined to abandon the technology immediately if it didn't
prove to be useful to me in pulling the weak ones out.  Trying to work
VK0IR from here in Central Texas a few days back was made a LOT easier
with the NIR-12 in use to reduce the noise level and help trim off-freq
signals from the headphones.  And, to make sure this note is OK with the
TenTec crowd, I never would have worked them either time without the new
Centaur amp!  It did yeoman's duty on 20m driving a Butternut HF2V
160-40m vertical!  (Working them barefoot on my Isoloop just did not
work at all.)

        73,  Duane  AC5AA

Duane A. Calvin      "All statements are mine only, not my employer's."
ac5aa@juno.com  -or-  duanec@prodigy.com
Day: dcalvin@austin.ibm.com

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