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[TenTec] Re: fix for Omni

To: <tentec@contesting.com>
Subject: [TenTec] Re: fix for Omni
From: paulc@mediaone.net (Paul Christensen)
Date: Mon, 21 Sep 1998 23:58:47 -0400
>What about using a diode switch to kick in a resistor across that xtal
>filter when the rig is keyed inorder to broaden the bandwidth? This would
>a really simple mod.

I started on a path toward building a PIN diode switch around this filter
and ran out of time in early July, prior to the start of my summer classes
in England.

Hey, maybe one of you guys can pick up where I left off?  Between the office
and law school, all I have time for is to post messages when I should either
be studying, working, or operating my Omni Six!  Anyway, this would be the
final hurdle to completing the necessary mods.  In the interrim, I'm using a
modified, slightly wider filter in that slot.

>Is it possible that the chirp on the leading edge is somewhat weaker than
>the desired carrier thus masking it during a poor communications path?

It could be Steve.  The effect of the chirp and being able to monitor its
effects on an oscilloscope is very interesting.  I would have never thought
that the trailing edge of the waveform would truncate as the CW TX BFO
frequency is adjusted lower.  The specified 9,000.400 kHz fixed CW BFO
offset is the rock-bottom, lowest point that this circuit is capable of
before the waveform completely falls apart.  Once you ever-so-slightly reach
the lower 2.4 kHz filter skirt, the ballgame is over.  At that point, the
transmitted CW signals start sounding like they're emanating from Havana or
<gulp> W1AW on 20-meters.  OK, that was uncalled for.  Maybe we can get the
W1AW ops to run code practice in the FSK mode for a couple nights.  I'll let
you make the call though!

-Paul, W9AC

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