[Elecraft] Re: BFO drift

[Kevin Cozens]

At 08:53 PM 11/03/2001 -0500, James Hammons wrote:
>       Keep in mind that reported drift among K2's varied a lot with
>some users reporting no drift of the BFO.   You can't really know
>whether you are improving your K2 unless you actually measure the
>drift.  From what I have seen I would guess that If your range, you
>wrote it down about the middle column 2 page 57 is near the low end of
>the acceptable 11.5khz range removing X1 or X2 will not help your K2
>and it already is low in VFO drift.  If your range is near the top
>25kHz, mine was 22.91 then removing the crystal helps a lot.

I haven't operated a lot on CW with my K2 and when I have, I used CW 
filters no tighter than 400Hz. As a result, I can't say I have noticed BFO 
drift. I do have VFO/calibration related drift. With both PLL crystals, I 
had a range of 22.24kHz. With X1 only, shift was 10.43kHz and X2 only had a 
shift of 10.15kHz. My K2 now has only X1 in place while I recalibrate and 
run some additional tests. For reference, my K2 is serial #2172, the PLL 
crystals are labeled 12.09-S, and the room temperature is about 64F.

By using a coil of wire placed near the back of the control board with one 
end tied to the antenna of an SW radio, I am now able to get enough of a 
signal from the 4MHz osc to calibrate C22 against WWV on 20MHz. WWV on 
20MHz wasn't that strong earlier but I have done a preliminary cal of C22 
against WWV. After running CAL PLL I measured my output frequency while the 
K2 was transmitting in to a dummy load. My actual transmitted frequency is 
consistently reading 110Hz to 120Hz low (as checked on 3.5MHz, 7MHz, and 
29.5MHz).

The method I developed of adjusting C22 based on the transmitted frequency 
of the K2 yielded frequency errors of no more than 30Hz (worst case on 
10m). However, once the temperature changed the calibration would vary 
across the bands (from 12Hz on 80m to 245Hz on 10m). If the error between 
display readout and measured frequency stays about the same for all bands 
for given temperatures I will be happy. It will be easier to 
predict/compensate for errors in the frequency readout.


Cheers!

Kevin.  (http://www.interlog.com/~kcozens/)

Owner of Elecraft K2 #2172        |"What are we going to do today, Borg?"
E-mail:kcozens at interlog dot com|"Same thing we always do, Pinkutus:
Packet:ve3syb@ve3yra.#con.on.ca.na|  Try to assimilate the world!"
#include <disclaimer/favourite>   |              -Pinkutus & the Borg