You hit the nail on the head Jerry. The effect of the CW transmit BFO
passing through the filter's steep knee not only exacerbates a slight chirp
emanating from the Omni Six's BFO board, but there are audible group-delay
effects from phase change. Thanks for pointing this out.
-Paul, W9AC
-----Original Message-----
From: Dr. Gerald N. Johnson, P.E. <geraldj@ames.net>
To: David E. Shelton <w4des@iolky.com>
Cc: Roy Koeppe <royanjoy@ncn.net>; tentec@contesting.com
<tentec@contesting.com>
To: <tentec@contesting.com>
Date: Sunday, January 03, 1999 6:17 PM
Subject: Re: [TenTec] Re: N4LQ and the 2.8kHz Pill
>
>The phase delay of a crystal filter changes rapidly at the knee. A
>little frequency shift could easily be magnified by that phase shift to
>sound like a wider chirp. It would seem to me to be best to make sure
>the CW signal was inside the filter a ways to get away from that. Either
>by selection of CW carrier frequency or filter frequency. Maybe it would
>be better to introduce a totally separate CW crystal oscillator that
>didn't need to go through the filter. I don't have any idea what that
>would do to the switching, but ought to make it sound perfect. Though
>its not easy to key a crystal oscillator without either clicks or
>chirps. The crystal doesn't like stopping and starting... Probably
>better to key a mixer to get a better on/off ratio that just keying a
>straight gain stage with the oscillator running continouously.
>
>73, Jerry, K0CQ
>
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>
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