Posted by
Don Wilhelm-3 on
Dec 06, 2004; 4:09pm
URL: http://elecraft.85.s1.nabble.com/Tuning-CW-Stations-in-160-meter-contest-tp372352p372353.html
Lee,
If you are using the default 1.5 kHz CW bandwidth for FL1 and listening with
a more narrow filter, the answer is 'quite likely'. Remember that the FL1
BFO is always used for transmit. This results in a filter alignment
situation that is seldom mentioned - that of transmit frequency offset.
This problem happens readily if you center the bandpass during filter/BFO
alignment and are using a filter wider than twice your sidetone pitch. If
you think about it, you should quickly determine that to actually center a
1.5 kHz bandpass on a 600 Hz point, the bandpass will be from 1350 Hz down
to -150 Hz -- yes, I said that right, the passband will cross over into the
opposite sideband! The more likely thing is that you did not set it up that
way, so the BFO for FL1 is shifted about 500 to 1 kHz from the remaining
BFOs. That is the reasoning behind my recommendations that CW FL1 be set no
wider than 2 times the sidetone pitch. The 700 Hz width is my preferred
normal CW receiving filter width, and I personally set my FL1 to 1.0 or 1.1
kHz to avoid having to shift the FL1 BFO far away from the other BFOs.
I do wish that the K2 in CW (and RTTY modes) always used the same BFO for
transmit as that used for receive, but such is not the case - FL1 is always
used for transmit in any mode (it is necessary in SSB mode).
If the FL1 BFO is not close to the same frequency as the BFO currently being
used for receive, your resulting transmit offset will be quite different
than your sidetone pitch. (Note: IMHO, a few tens of Hertz will make no
noticable difference, but hundreds of Hertz difference in the BFOs will be
objectionable.)
Wayne - would it be possible to change the firmware to use the same BFO for
transmitting and receiving for all modes except SSB? Or is my analysis
incorrect here?
73,
Don W3FPR
----- Original Message -----
> I participated in the 160 Meter CW contest this weekend with my K2/100 and
> noticed something I had never noticed before. I think that I might have a
> misadjustment in the filters and I am not sure where.
>
> I would tune a station (S&P) to where I thought I was in the bandpass of
> the RC station. At least the note sounded good to me. Invariably, I
> would have to tune about a tenth of a KC down to actual make the contact.
> I could call on the higher tone and they would not hear me, but calling on
> the lower tone they would come back all the time. I have the filter
> center set at 700 with filters widths at 1.5 - 700 - 400 - 100.
>
> Do I have something set to low or to high with the BFO? This gets
> confusing to me.
>
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