Privet Igor --
As best I can remember, we used MCU v1.66 and DSP 1.52.
I didn't use the AGC because I did not need it. The point of
automatic gain control is to adjust the gain of the various stages of
the receiver in order to
a) avoid distortion/overdriving a stage, and
b) bring signals up/down to a comfortable listening level.
(b) is not relevant to an operator who is working a pileup. (b) is
relevant to an operator who is monitoring a frequency with one station
transmitting.
For operating a pileup, there are a variety of tools the brain uses
to distinguish the many signals:
-- pitch (CW)
-- style of speaking (speech) or keying (CW)
-- artifacts; e.g., auroral flutter, chirp, etc.
-- strength (all).
AGC tends to reduce the difference in signal strength, and so removed
valuable information.
In situations where static crashes interfere with reception, AGC hang
time on a loud static crash also increases the length of time that a
specific static crash interferes with reception.
I used headphones with good audio isolation between my ears and the
rest of the world around me. That allows me to set receiver gain levels
with the underlying antenna/band noise just above my threshold of
hearing... and to use at least 80 dB of my hearing range for listening.
In this quiet listening environment, I don't need AGC.
Even in a less-than-quiet listening environment, if a band is just
open weakly (e.g., 12m to Europe), the range of signal strengths in the
pileup can be smaller: maybe less than 30 dB between band noise and the
strongest signal. So AGC isn't needed here either.
My ideal AGC in these situations is one that only makes changes in
receiver gain when a stage in the receiver is about to be over-driven
(e.g., the A/D converter)... and removes those changes relatively
quickly. Even then, it might be fine to allow the receiver to be
over-driven (a static crash contains no information). If a signal I
want to copy is over-driving the receiver, the best solution often is to
reduce the RF gain manually during the duration of the time when I want
to copy that station. If that station is just "interference" (e.g., a
loud USA station on 80m CW calling VP6DX, when I want to work northern
Scandinavia and northwest Russia/western Asia during the brief opening),
I have other controls (filter bandwidth, notch) than might be better to
use that gain reduction (automatic or manual) that could suppress the
desired weak signals.
So, almost any AGC system is inappropriate for a DXpedition or
content environment... as long as the receiver and one's own ears have
enough dynamic range to handle all the signals presented to it. The K3
has more dynamic range than other receivers.
73,
-- Eric K3NA
on 08 Mar 13 Thu 02:26 Igor Sokolov said the following:
Almost all of the operators ran the K3 with AGC off (all modes).
-- Eric
Eric, can you explain what did you not like about AGC in K3?
Did you notice any problems with DSP being permanently on in K3 when
listening to heavy pile ups?
73, Igor UA9CDC
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