[Elecraft] K2DSP Spectrogram images

[Ron D'Eau Claire]

You won't see a difference when using a noise source, Dave.=20

AGC becomes an issue when sweeping the bandpass with a discrete signal. =
Or,
in the case discussed here recently, in tuning the K2 across a signal =
and
measuring the  loudness of the signal as it is tuned across the =
bandpass. Of
course, as far as the filters are concerned, they are both the same =
thing.=20

When you are listening to a single signal, such as the 4.000 MHz birdie, =
the
AGC will constantly try to keep the audio level constant. So, as the =
signal
grows weaker as the tuning puts the signal down on the slopes of the =
filter,
the AGC turns up the gain to compensate.=20

When you use a noise source like you did with spectrogram, the noise =
itself
blankets the bandpass, suppressing the AGC. As long as you don't vary =
the
noise coming into the antenna jack, the AGC won't change. That gives you =
a
clean, accurate view of the filter bandpass.

Ron AC7AC
K2 # 1289

-----Original Message-----
Hi again Gang

I've just posted "with" and "without" Spectrogram images on my web site.
Images are shown with 400 Hz, 200 Hz and 100 Hz bandwidth settings. AGC =
on
or off doesn't seem to make any difference to the results.

http://www.astromag.co.uk/k2/dsp/

73 Dave, G4AON