[Elecraft] Spectrogram - Again

[Ron D'Eau Claire]

John makes a good point about doing a Spectrogram alignment AND it is
useful when simply operating the K2 on the bands.

While the noise generator is handy, there is NO need for it to set up
the K2 BFO frequencies. "Band noise" on 80 is more than enough to do a
perfect alignment job. The only advantage of the noise generator is to
avoid any signals in the passband. You don't want any "real" signals in
the passband while doing the filter alignment. But I've never found it
difficult to find a 2 kHz chunk of band down around 80 or 160 where I
can't hear signals. 

Also, turn the "RF GAIN" down! It even helps to turn the AGC OFF. Then
set the Audio Gain about 1/4 the way up and control the signal output
using the RF Gain control, not the audio gain control. The "bandpass"
will then rise neatly out of the base line on the Spectrogram display.
Be sure to plug the sound card into the AUX SPEAKER jack, NOT the Phones
jack, if you want to see what the bandpass really looks like on SSB. The
phones jack output will show a slope on the bandpass that is NOT really
there. 

In fact, controlling the volume with the RF Gain is an excellent way to
operate the K2 on the air, too. Running the RF Gain full up and using
AGC is nice for roaming around the bands, but I much prefer to turn it
off and adjust the level with the RF Gain when in a QSO. It makes the
signals stand out much clearer above the background noise! That's
because when the RF gain is full up and the AGC is on, the AGC keeps
turning up the gain between code characters so the noise in the phones
or speaker as always the SAME as the signal! Using "Slow" AGC helps,
because that keeps the AGC from turning up the gain so quickly between
dits and dahs, but even a brief space in sending allows the AGC time to
pump the noise up to full volume. Personally, I'd rather listen to the
signal and let the noise stay down in the background where it belongs...

Ron AC7AC
K2 # 1289


After a lot of fiddling, two things became apparent. I was setting both
the N0SS noise generator and the K2 AF gain too high. Using the output
pot to set the noise generator just above receiver noise on my
headphones and then setting the K2 AF gain to minimum and increasing it
slowly, the desired shapes began appearing. I'm guessing my computer's
soundcard was clipping even at moderate audio levels and the FFT
processing of the resulting "squared" waves in Spectrogram resulted in
all those interesting peaks.

John, K7JG and K2 #1932.


_______________________________________________
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