Re: P3: a modest proposal for QSY

Posted by Bill W4ZV on Aug 13, 2010; 1:17pm
URL: http://elecraft.85.s1.nabble.com/P3-a-modest-proposal-for-QSY-tp5410950p5419946.html

Guy, K2AV wrote

Actually...

In a CW contest, where following packet spots can put you on the exact
same frequency with all the other braying lemmings, contributing to
your signal's non-pickoutable status at the other end, being off the
crowd frequency by 20-50 hertz is a SUCCESSFUL strategy to break
through the pile, practiced ON PURPOSE by top CW contest operators. If
you are following CW packet spots, best to set your XIT up or down
20-30 Hz and leave it there.  DON'T ever use zero offset chasing CW
packet spots.  (It will NOT bother me in the LEAST if all those who
read this think such an assertion is nonsense and never try it out.  I
have outlined one of my competitive edge secrets, and I WON'T mind if
you DON'T use it.)

So being within 50 Hz is QUITE adequate and USEFUL.  And despite given
what seems to be being played as some failure of the P3, one DOES
still have the K3 tuning knob to very quickly adjust to perfect
centering for RTTY, and digital modes.  On the K3, it's the big
easy-to-use same-size-as-the-maxi-boxes knob.  For other transceivers,
consult owner's manual for location and instructions for tuning knob.

50 Hz off will still be within the audible passband on the NARROWEST
K3 passband setting.  Most contesters will use something like 200 or
250 for search and pounce, especially for chasing packet spots.  Many
of these spots will be off 100 or 200 Hz, in addition to carrying
blown calls, which is why the need for a quite wider bandwidth than 50
Hz for any kind of search and pounce operation.

I strongly disagree.  Ideally, the P3 should send the receiver VFO (not the transmitter) to exact zero-beat (as CW Skimmer does).  If you *then* choose to set XIT for a consistent + or - 50 Hz offset, that's very easy to do.  If the receiver does not go to zero beat, you have no way to set your consistent 50 Hz offset and in fact will be randomly between 0 and 100 Hz off, depending on which side of zero-beat the P3 sends the K3 to (+50 +50 = +100, and -50 +50 = 0, where VFO is the first number and XIT is the second).

The lack of true zero-beat capability is the major missing piece in the P3 and is why I'll continue to use CW Skimmer (even with its 24 kHz limitation) with my K3.  Alan is very aware of this need, there are multiple implementation possibilities, and I'm sure he'll find the best solution.  But I would not like for him to walk away from this discussion thinking true zero-beat capability is not needed.

73,  Bill