[Elecraft] Frequency shift

[George, W5YR]

Julian,

One of the side benfits of my using the K2 as a down-converter for my Icom
PRO is that I *can* get one Hz resolution as well as correct the dial
reading to be spot on over a given segment of a band. PSK31 thus becomes a
snap assuming that overall drift of the K2 is not too bad. Actually in one
down-converter mode that I use (there are two), the BFO is not involved and
only the VCO drift need be corrected.

The trick, of course, is not to tune the PRO to the "correct" frequency -
which I promise to explain when I get the article written - exactly, but to
use it as a tunable IF allowing for one-Hz frequency changes and dial
correction of the K2.

Quite a powerful bonus obtained by wedding the K2 front end to the PRO
IF-DSP.

Sorry I can't give you "better than one Hz resolution!"

73/72, George    
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121


"Julian (G4ILO)" wrote:
> 
> I don't know what results you got, Chas, but I tried Earl's method and it
> didn't make the slightest difference here.
> 
> In fiddling around, I did apparently get the standard and narrow filters in
> RTTY mode spot-on using the 14MHz birdie as a reference point. But
> listening to actual PSK signals in the 14MHz band I found that switching
> from wide to narrow would result in a frequency shift ranging from -4Hz to
> +17Hz approx, depending on the frequency of the transmission being received
> (in the 14.070 - 14.072 region.) This concurs with my understanding of the
> effect of limited DAC resolution that have been explained to me by several
> people, so I wasn't at all surprised. But I was prepared to give it a try.
> 
> Perhaps for some people who only use CW not PSK the frequency change is too
> small to be noticeable by ear. Unfortunately it's still too great for
> convenient use in data modes (which wasn't an application envisaged when
> the K2 was designed, as several folks have pointed out).
> 
> The K2 mod I await most keenly is the one that gives better than 1Hz
> resolution for both the VFO and BFO. :-)
> 
> 73,
> --
> Julian, G4ILO. (RSGB, ARRL, K2 #392)
> Homepage: http://www.qsl.net/g4ilo
> 
> Charles Greene W1CG@QSL.net wrote:
> 
> Earl,
> 
> I find it hard to believe you got all filters without a frequency
> shift.  If you send Julian a copy of the procedure, please include me too.