[TenTec] OMNI VI Chirp Report

[Paul Christensen]

Don's input helped to shake some cobwebs loose...

TT initially shifted the CW BFO from the USB crystal.  Then, I believe in an 
effort to help eradicate the chirp, a later design shifted the LSB crystal 
up since the excursion to 9,000.400 kHz was smaller.  The frequency stayed 
the same, but the manner in which to get there changed.

If you compare schematics of an older VI and a recent VI+, I am confident 
you will see opposite crystals being pulled in the CW TX state.  However, 
this created a related dilemma in that the two Control Boards are also 
slightly different as it is the Control Board that selects which xtal to 
shift during CW transmit.

I found some of my archived messages from ten years ago.  Those of you not 
yet fully "fed up" with this discussion may want to have a look.  I also 
forgot about a test I used in determining chirp: If you switch to FSK, the 
Omni will key in CW as normal but without a side-tone.  Now, using an 
external receiver, compare the resulting CW note between transmitting in FSK 
mode and CW mode.  In most cases, FSK will sound better on another receiver. 
The reason is that the FSK frequency was not being pulled as far as the CW 
BFO frequency.  Here are the links to the specific archived messages.

http://lists.contesting.com/pipermail/tentec/1998-September/006782.html

http://lists.contesting.com/pipermail/tentec/1998-September/006793.html

http://lists.contesting.com/pipermail/tentec/1998-September/006807.html

Paul, W9AC