[TenTec] RE: [No Subject]

[Duane Calvin, AC5AA]

As I reported last year, the small amount of microchirp I can detect on my signal is completely gone when I use FSK mode instead of
CW.

  73, Duane   AC5AA

------Original Message------
From: "Paul Christensen" <paulc@mediaone.net>
To: geraldj@ames.net
Sent: July 11, 2000 7:05:39 PM GMT
Subject: [No Subject]


<396B39A0.7076@ames.net>
Subject: Re: [TenTec] OMNI VI <bleeping> CW note
Date: Tue, 11 Jul 2000 14:06:28 -0400
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> Sounds fine on my Corsair II no matter how I try to tune it to be
> critical. Could it be that there's just a tiny microchirp on the edge of
> the filter that when you tune to the edge of a receiving Omni VI filter
> is converted to that click...

Yes, but the microchirp is being magnified by the Omni's 2.4 kHz filter
skirt on the W1AW transmitter.  The effect is also more noticable on
receivers employing ladder filters rather than lattice filters which tend to
ring more and thus mask the true transmitted effect.  I believe that Steve,
N4LQ was one of the first to point this out.

To validate all of this, W1AW could simply place the transmit mode into FSK
which moves the BFO transmit offset frequency further away from the sharp
skirt of the 2.4 kHz filter.  In nearly all cases, the Omni Six Plus sounds
substantially better on CW when it is keyed in the FSK mode, not CW.  Of
course, an external keyer must be used; I don't believe the internal keyer
can be used in FSK.  Incidentally, all other circuitry is the same while
keying in the FSK mode, including the integrated wave-form ramping circuit.
Those of you who are using an Omni Six with an external keyer, try the test
yourself: critically listen to your transmit CW on an external receiver
(using wide IF bandwidths) while toggling between CW and FSK on the Omni.
Let us know your results.

> Is there something about the fast AGC in
> the receiving Omni VI in QSK mode that's hardening a slightly hard
> leading edge? Does going to slow AGC affect the perceived signal?

It make exacerbate the effect, but the root-cause is clearly in the
transmitter.

-Paul, W9AC

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