[Elecraft] Calibration of BFO

[Don Wilhelm]

Rich,
It sounds to me like you are using a single signal rather than a wideband
noise source ('dead band' noise will do) when using Spectgram.  When using a
single carrier to attempt to set things up the result is just like you
describe based on my previous experience.  The problem is that the single
signal may not actually be set in the exact center of the filter passband,
and when you change the BFO, the display of the received frequency will
shift by the amount you moved the BFO - then you retune the desired signal -
and then do it all over again, and again and again ....

Try using a noise generator or band noise (with no signals present) along
with Spectogram and I believe you will have better luck.  You may have to
re-do it several times to take out a very small frequency shift (10 to 30
Hz), but you should get within 20 or 30 Hz on the first try.

Yes, set the SSB BFO first - that is the BFO that is used for transmit.
Ideally this BFO should be set to provide the best transmitted SSB and may
depend on your particular voice characteristics.  Making a tape recording
with another receiver is the best way to do that evaluation.

73,
Don Wilhelm  - Wake Forest, NC   W3FPR home page: http://www.qsl.net/w3fpr/
  QRP-L # 485   K2  SN 0020   mailto: w3fpr@arrl.net

----- Original Message -----
>
> I am having trouble setting up the center frequency of the narrow bandpass
> filters (FL3 and FL4). I have gone through the "Calibration Functions"
> section of the manual and each of the various and many guides on how to
use
> "Spectrogram," however, it seems like one correction offsets the other. I
am
> fairly sure how to adjust the bandpass width, but get confused on
adjusting
> the position of the bandpass and the BFO.  The band pass is at the desired
> width but when I try to get it at the desired center frequency, the
received
> frequency is shifted.  For example, when I try to setup a 1.00 kHz
bandwith
> centered at 1.00 kHz for FL4 on USB (20 Meters) for PSK, the received
signal
> shifts by more than 50 Hz. If left this way, a QSO ends up "walking" up
the
> band with each exchange.
>
> I am trying to get the minimal change of the received frequency with the
> desired bandpass centered on the desired frequency. Could you please
explain
> how to adjust: 1. The center frequency, 2. The BFO, 3. The Band-width, and
> 4. Which order to adjust these.  Is there any interaction with these?
Should
> I run CALL PLL between any of these adjustments?  Should the CW, USB or
LSB
> be set first?
>