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[TenTec] Adding band to Omni D Series B

To: <tentec@contesting.com>
Subject: [TenTec] Adding band to Omni D Series B
From: N4NT@chartertn.net (Mike Hyder -N4NT-)
Date: Wed, 19 Jun 2002 09:11:00 -0400
Hi, Ken--

Put the crystal in it and then try it out, listening on a separate receiver
or viewing the output with a spectrum analyzer.  It is at that point you may
understand of what it is that we speak.

Here is my experience:
I put my Omni-C on the 18 MHz band and found that it was putting out one or
two watts with the key up.  Then I listened to its output with another
receiver and found other signals being produced by the Omni.  My crude
analysis of the problem revealed the following:

The PTO operates from 5 to 5.5 MHz.
The band crystal for the 18 MHz band oscillates at 4 MHz.
The mix of these two frequencies gives what the manual calls the "VFO
Output" from 9 to 9.5 MHz.

The carrier oscillator operates at the following frequencies:
SB-N  9,000.000 kHz
CW     9,000.750 kHz
SB-R   9,003.000 kHz

In theory then, to operate at 18.100 MHz on SB-N, the VFO Output will be
9,100.000 kHz and that will mix with the carrier oscillator of 9,000.000 kHz
for an output of 18,100.000 kHz.  So far, no trouble with the theory.

In practice, however, I found that my Omni-C was also transmitting on the
second harmonics of both the carrier oscillator and the VFO Output
frequencies.  So, in addition to the 18,100 signal, I had outputs at 18,000
and 18,200 kHz.  I called Garland Jenkins (I believe this was before Paul
Clinton's time) and told him of the trouble and asked for a fix.  His
response was, "Get a Corsair."  He told me that it would be nigh onto
impossible to fix my Omni to operate properly on the 18 MHz band.  In fact,
that is the biggest reason Ten-Tec changed its mixing scheme in the 580
Delta and Corsairs.

I have a friend who has used an Omni on 18 MHz and swears that his signal is
clean, but everyone else who has told me of his experience reports trouble.
Give it a shot.  Maybe Paul Clinton fixed that Omni that you bought so there
will be no trouble.  If he did, please let us know how he did it so we can
all modify our Omni's.

And that is all I know about that.

73, Mike N4NT

----- Original Message -----
From: "Ken & Linda Burrough" <w8keb@1st.net>
To: "Ten-Tec @ Contesting. Com" <tentec@contesting.com>;
<geraldj@isunet.net>
Sent: Wednesday, June 19, 2002 8:04 AM
Subject: Re: [TenTec] Adding band to Omni D Series B


> Hi All
>
> Now I am confused, at the last Ten-Tec Hamfest I bought a Omni C from the
> Used Equipment case.  Paul Clinton told me this Omni C can be put on 18
MHz
> by putting the crystal in it.  He said this one will work with NO Harmonic
> Problems.  Ok, now who is right?
>
> Steve, N4LQ has always said the QSK on the Omni C was the best, and he is
> right.  Steve it is because of you I now have the Omni C and am very happy
> with it.
>
> Ken/w8keb



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