Some will remember the thread a few months back in which I described the
problem I had been having making contacts with the Omni VI opt 3 I have. I
realized there was a problem with the radio when I used my 706MKIIG at 5
watts one day in a QSO party with the same antenna and made contacts all
over the place no problem.
It turns out the radio is off somehow by about the amount of the sidetone,
so when I zero beat a CW station (match tone set in sidetone) and transmit,
the other station hears no tone. My signal is below his audible range
and/or outside his passband.
We did some testing here between the 706, the Omni and other stations and
determined that the problem could be gotten around by setting the XIT on to
-whatever the sidetone was, in my case, usually 700Hz. That made the radio
work, except for the transmit frequency being off, and hopping around with
QSK, but it put my signal at the frequency that other stations would hear
it.
I was not content to leave it like that so sent it to TenTec to check the
alignment and/or correct whatever was occurring to cause this. To my
chagrin, Paul reported that the radio was just fine, working as designed,
no problems, aligned just fine working per factory spec, nothing needed,
etc., and sent it back. At least he didn't charge me for this.
About that time, I found a Omni VI+, with full filters and speaker/power
supply at a price that I found attractive, so I bought it. I've been using
it for more than a month, works great, just the way you expect, and have no
trouble making contracts, in the context of a 100 watt radio with a so-so
antenna anyway. I used it for Field Day at 5 watts output to a homebrew
S9v31 vertical and was very pleased with the performance, given the
circumstances.
This Omni VI still bugs me though, so I set up all three radios and did
some testing. I set all three radios on 14.030, using the no output on the
two Omnis and a dummy load on the 706. When I transmit using the 706, I
hear that signal on 14.030 in the Omni VI+, and at 14.030.4 zerobeat on the
Omni VI, in both cases matching the tone using that function on the CW
button. Both sidetones are set at 700Hz.
When I set the Omni VI to 14.030 and transmit, I zero that on the Omni VI+
at 14.030.04, a 40 Hz difference. On the 706, I zero the signal at
14.030.07. There is a slight difference in the calibration of these 3
radios, and they sometimes vary 10 Hz or so anyway.
When I hear the Omni VI+ and zerobeat that signal in the Omni VI, it is at
14.030.42. In a QSO, I would hear the Omni VI+ calling and zero that
signal. When I called using the Omni VI, on the zero frequency, I hear it
in the VI+ as a very low pitch, almost a buzz. When I turn on XIT, at
-700Hz and call, the Omni VI+ hears it with a higher audio tone, and zeros
the Omni VI signal at 14.029.79.
It looks to me like perhaps the Omni VI is off calibration slightly, but
that doesn't explain why it doesn't transmit with the proper offset as
expected, without XIT being on anyway.
I tried a QSO with these three radios. I call CQ using the 706, I "hear"
and zero that signal on the Omni + at 14.030, the same as the 706. I reply
using the Omni VI+ and hear the reply in the 706, with a ~700 hz. tone. I
hear and zero the same signal from the 706 using the Omni VI, at
14.030.39. When I reply to the 706, the 706 hears a strong signal at a
very low audio tone, inaudible. When I click XIT -7 on the Omni VI, I hear
it in the 706 just fine.
I have consulted off list with a very clever and exceedingly knowledgeable
Tentec user, who probably wishes to remain anonymous, and he has suggested
I check the alignment myself. This fellow also suggested a way to
determine if one or more of the parts in the affected circuit have gone
bad. I do not have a frequency counter, and do not know where to obtain
access to one. What kind of frequency counter ought to be used for this?
Is there anyone who works on these radios, other than Tentec, who has the
test gear etc to resolve this?
There has to be an explanation why the VI doesn't work like the VI+ in this
respect.
TIA
73 de W6OGC Jim Allen
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