[TenTec] My new ORION

[Bill Tippett]

I wrote:
 >Mark, I suspect this is related to the same DSP
overload issue.

         While making my daily bike ride to the Post
office, I was thinking more about this issue.  In
both the CQ 160 CW Contest in January and in the
ARRL DX CW Contest (SOSB/160) in February, I do NOT
recall having any distortion problems.  I was then
using 1.373b4 since I'm a beta tester and I found
this comment in the version history:

 > Version 1.373b4
 > - Eliminated passing of AGC info to DSP. This was causing Out Of Band
 > distortion when used.

Nevertheless, I HAVE noticed in-band distortion at
times since then and believe there could be at least
3 different issues involved in your situation:

A.  Which roofing filter were you using when you
noticed the problem?  If you are using anything in
Orion's 500 Hz slot, that is a known problem for
degrading IMD and you can solve it by simply
disabling that position.  If you want a narrow
filter with even better IMD than the stock 1 kHz,
Inrad's #762 improves Orion's already exceptional
IMD performance by 6-10 dB at 2-1 KHz spacings.

http://users.vnet.net/btippett/inrad_.htm

B.  Is the distortion on in-band signals
or are you hearing out-of-band generated IMD
products (sounds like code other than Morse)?

If the former, this is the same problem I've heard
but there may be a simple work-around.  Until I
learned how to use the "new" RFGAIN control, I
always set AGC Threshold fairly high (e.g. 20 uV
on 160m and never below 3uV on 10m).  After I
learned how to use the new control, I simply
set 3uV for everything and then used only RFGAIN.
It may be that I began noticing the distortion
problems after doing this.  The problem you can
run into is that you can "waste" the DSP's dynamic
range by setting Threshold too low, and there is
no limit on the upper end due to the FW bug.  A
simple work-around may be to set AGC Threshold
to 3uV or higher (no need for it to ever be lower
than 3uV on ANY band), then listen on the band
of interest with RFGAIN fully CW.  Turn RFGAIN
back fully CCW (0%), and advance it until the band
noise sounds the same as full CW.  This should be
well below 100%, and now the DSP will have more "top
end" before distortion occurs.  I agree it should
be impossible to overdrive the DSP but this might
be a work-around until Ten-Tec fixes that bug, and
it also seems to explain why I never had problems
in 160 contests in some of the worst QRM known to
mankind.

If the latter in B above, and you do not have
a bad roofing filter, then there may be something
else wrong with your unit.  But it is definitely
a specific problem and not generic to all units
or Orion would not perform so consistently well
in 4 independent tests.  It could be the "Out
of Band" distortion problem in 1.372 mentioned
in the 1.373b4 release is causing this problem.
Unfortunately Ten-Tec has not yet released this
so I cannot send a copy to you to try, and they
are now totally focused on the 2.0 rewrite and
we don't want to distract them from that.

         Another suggestion is to simply call Paul
Clinton at Ten-Tec.  If you haven't experienced
Ten-Tec service before, you're in for a pleasant
surprise!

                                 73,  Bill  W4ZV