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Re: [TenTec] OMNI6 PLUS Alignment procedure needed

To: tentec@contesting.com
Subject: Re: [TenTec] OMNI6 PLUS Alignment procedure needed
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net,Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 29 Dec 2007 19:59:41 -0600
List-post: <mailto:tentec@contesting.com>
On Sat, 2007-12-29 at 13:53 -1000, Ken Brown wrote:
> Hi John,
> The information needed to perform a complete alignment of an Omni VI may 
> in fact be contained in the manual. However it is not all in one place 
> and listed in the most efficient order. Each of the circuit boards has a 
> text description of how the circuits are supposed to work, and in most 
> cases how to adjust them. A start to finish list of adjustments, in the 
> best order to do them, for the whole radio, not just individual boards, 
> would be nice.
I may be out in left field look the wrong way without ever seeing the
Omni circuits or manual. But there could be some weird interactions
around the BFO/carrier generator frequency settings.

As I recall, the CW BFO crystal is shifted in frequency for transmit. No
doubt it has separate trimmer capacitors for each frequency and probably
the manual says trimmer A sets receive and trimmer B sets transmit.
Trouble is that in one mode both trimmer A and trimmer B affect the
crystal and if you set one trimmer with both in the circuit, then set
the other mode, the first setting is now off and you go back and forth
for a while because of the excessive interaction. What's needed is to
set the trimmer that is alone for its mode, then change mode and set the
other. There might not be much interaction, but there could be some
capacitive coupling in the trimmer switch. To require a couple repeats. 

Otherwise I can't think of any other place for there to be significant
interaction so long as the alignment proceeds from amplifier chain input
to output. If the loads aren't exactly the same when a tuned circuit is
switched between transmit and receive, it may be necessary to optimize
one and accept the lack of optimization on the other or to try for some
sort of compromise.

73, Jerry, K0CQ

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