[Elecraft] Calibration of BFO

[David A. Belsley]

Dave:
  My experience differs somewhat with yours.  I find that if I attempt to=20
adjust a single filter, the shift can (and usually does) become larger.=20
So, if I want to adjust a single filter, I adjust that filter and then I=20
reset all the filters, starting with number 1, in succession (including the =

one just adjusted).  By resetting the filter I mean: I note its setting,=20
move the setting several numbers down and then back again to the original=20
and shift to the next filter (I do this for both the c and cbar filters=20
when doing this on cw).  The least shifting occurs for me after I have set=20
all filters in this manner in rapid succession.  This procedure works well=20
even if you have not reset any filter but simply notice after a period of=20
time that there seems to be increased shifting.  Simply go and reset every=20
filter back to its original value.  When I do this, I notice that the shift =

is either gone altogether (rarely) or has only one 10Hz jump somewhere=20
along the line (typical).

best wishes,

dave belsley, w1euy

--On Monday, February 4, 2002 9:17 AM -0500 Dave Gingrich K9DC=20
<gingrich2@dcg.org> wrote:

> At 07:28 2/4/2002 -0600, Tom Hammond N=D8SS wrote:
>
>> Consider NOT using the OP1 filter for PSK31. You can set the other three
>> filters FL2 thru FL4 to wide mid and narrow bandwidths as well...
>> possibly, you can find settings which don't shift using strictly the CW
>> filters.
>
> Only problem is OP1 is always used on transmit so you need to minmize the
> shift between OP1 and the chosen receive filter, even if you never use
> OP1 to receive.
>
>> Note that it is NOT at all unusual to have a 10Hz - 20Hz frequency shift
>> when switching between filters. If you managed to get it down to 0Hz
>> shift, it was almost a fluke.
>
> I have found that you can get the shift reduced to less than 1 Hz by just
> repeating the procedure numerous times. Sometimes by just adjusting one
> filter at a time.  Often I just go in to the procedure and just the BFO
> by one 'notch' and back again and exit, so it will recalculate the
> offset.  I have been able to get it down to the point where there is no
> audible pitch change (musicians ear) between the filter settings, and
> just a slight phase twist on the PSK tuning eye.
>
> It WILL drive you nuts, but it can be much better than 10 - 20 Hz.
>
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> Dave Gingrich, K9DC - Indianapolis, Indiana  USA
> K2 #2211, K1 #931, QRP-L #2376, ARS #1109,
> FPQRP #389, IRLP #473, k9dc.ampr.org, CCIE #6748
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
> _______________________________________________
> Elecraft mailing list: Elecraft@mailman.qth.net
> You must be a list member to post to the list. Postings must be plain
> text (no HTML or attachments). See:
> http://mailman.qth.net/mailman/listinfo/elecraft Elecraft Web Page:
> http://www.elecraft.com



----------------------------
David A. Belsley
Professor of Economics