[Elecraft] Spectrogram - Again

Wed Dec 11 22:49:00 2002

One other setup detail is to turn off the audio filter (if you have that
option) using the slide switch on the PC board.  If this switch is on, the
low pass hiss filter is on, even if AF1/AF2/OFF is 'OFF' on the audio filter
menu.  Both this and using the headphone jack (with it's own low pass hiss
filter) will really roll off the Spectrogram plots.  I spent months
troubleshooting my KSB2, trying to get a "flat" response, only to find out I
had both low pass filters activated.

73,
Ed - W0YK

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Ron D'Eau Claire
> Sent: Wednesday, December 11, 2002 6:20 PM
> To: [email protected]
> Subject: RE: [Elecraft] Spectrogram - Again
>
>
> 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.
>
>
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