Re: LF: TF3HZ

[Bill de Carle <ve2iq@magma.ca>]

At 01:06 PM 11/20/2011, Markus DF6NM wrote:
[..]
> BTW Stefan's strong DFCW signal is producing an unusual modulation effect
> on Halldór's grabber, as both the background noise and all other signals
> seem to brighten up during the dashes. Just like a kind of negative
> AGC...

I noticed that happening on my grabber here - at first I thought it might
be high resistance in the T/R relay contacts of my TS-850 (the banding is
not particularly correlated with Stefan's dashes).  I receive a
relatively strong signal from Mitch, VE3OT, who sends QRSS "MP"
- it is outside the screen range of my grabber but I still hear it
well.  Even though my TS-850 AGC is turned off, I know the soundcard
in the netbook I'm using has a lot of audio compression built in and I
have to keep the audio level quite low to expect any kind approximation
to a linear response.  Possibly the more-noise / less-noise banding
on the SL display is caused by local signal from MP keying the
compression circuit in the soundcard?  Tonight I'll try to reduce
the local signal with some slope-tuning high-cut to see if it improves
things.  There is also an IF notch filter on the TS-850 I haven't
tried yet.

73,
Bill VE2IQ