Lee and folks,
I was all wet with my response this morning about the wide CW filter
settings - I just tried various settings of filter widths, and BFO settings
that are quite skewed from normal.
What I found is that as long as the BFO is positioned so that any part of
the passband contains the sidetone pitch frequency (as observed on
Spectrogram), the transmit frequency will be equal to the frequency of a CW
signal being received AT an audio tone EQUAL to the sidetone pitch. So wide
filters are OK, and you can position them most anywhere within reason - it
will not change the transmit frequency.
Wayne has done some fancy stuff with frequency control in the firmware!!!
and it works.
I also found with my playing around with different BFO settings, that
changing the BFO frequency setting will NOT alter the pitch change when
switching from filter to filter. Any change in pitch when switching filters
can be blamed on only 2 things - 1) the signal was not tuned propery to
equal the pitch of the sidetone, and 2) the normal DAC variation found in
the K2 - this should be 30 Hz or less (I typically observe a 10 Hz
difference on Spectrogram). I do recall that Wayne wrote a long post about
how the K2 maintains pitch on a signal, and I guess I did not digest all of
it at that time. I must review that post given the revelations I had with
my testing today.
Bottom line - zero beat the signal carefully and the transmit frequency will
be that indicated on the K2 frequency display (or at most 30 Hz away). The
other operator must be also listening on that frequency, and in a contest,
he may have forgotten to turn RIT off, or perhaps he is working stations a
bit off his frequency intentionally to reduce the QRM??? Who knows what may
be going on at the receiving end, but your K2 is likely to be correct (as
long as YOU don't have RIT or XIT turned on yourself).
73,
Don W3FPR
----- Original Message -----
From: "W3FPR - Don Wilhelm" <[EMAIL PROTECTED]>
To: "Lee Buller" <[EMAIL PROTECTED]>; "Elecraft Reflector"
<elecraft@mailman.qth.net>
Sent: Monday, December 06, 2004 11:09 AM
Subject: Re: [Elecraft] Tuning CW Stations in 160 meter contest
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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