[ICOM] IC-7000 AGC

[Adam Farson]

Hi Scott,

In the IC-7000, both the AGC and the NB are DSP processes. I suspect that
the NB process is inside the AGC loop, so it should be possible to adjust
the NB so as to remove fast-rising noise impulses which might -
theoretically - trigger a fast AGC response.

The NR process is post-AGC, so it will not be of too much help in this case.

You may be able to generate a test signal if you can borrow an RF signal
generator with a pulse-modulation input, and modulate it with a square-wave.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Scott Honaker
Sent: Friday, June 08, 2007 09:29
To: icom at mailman.qth.net
Subject: [ICOM] IC-7000 AGC

> http://www.sherweng.com/documents/Dayton2007w.pdf

I do wish I'd attended this talk.  It's not clear to me what real-world
conditions cause this to happen.  At home I have to deal with an electric
fencer that creates ~S5 broadband noise.  I find the IC-7000 noise blanker
to be incredibly effective removing this impulse noise and haven't noticed
side effects.  

The implication is that the impulse noise has to be <1mS to be troublesome
to the AGC.  I suspect the difference between the impulse noise and desired
signal strengths would have to approach the dynamic range of the ADC before
it would be an issue.  I don't have a shack full of toys to test this but am
interested in duplicating it.  

He mentions "Same problem on unblankable line noise".  That implies there
might be a feature in the DSP to reduce/eliminate this problem (noise
blanker, noise reduction, AGC response time, filter width, auto/manual
notch, etc.).  I'd like to try that out.

I don't have a good way to measure the pulse width of a fencer but
intuitively I'd say it's pretty short.  I could move an antenna closer to
the fence to exaggerate the intensity relative to incoming signals.  Any
other suggestions for real world duplication scenarios?

Thanks,

Scott N7SS




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