Ed ....
If I understand what I think you said, the agc settings are
dependant on:
Pre-amp on/off and / or Attenuator on/off
The DSP filter width
Which 1st IF filter is active
and .....
the AGC SLP and THR settings are, for the most part a
well kept secret and not to be shared.
However mine are SLP= 8 and THR= 4 and, to me, it
sounds pretty close to the K2. I don't use NR much on
CW because of what it appears to do to the received CW
signals.
This is with MCU 2.34 and DSP 1.81, which may affect
how those two settings are set.
If SLP= 8 and THR= 4 are bad settings, please tell me
why.
73 Hank K8DD
----- Original Message -----
From: "Ed Muns" <[EMAIL PROTECTED]>
To: "'Mike Kasrich'" <[EMAIL PROTECTED]>
Cc: "'Elecraft'" <elecraft@mailman.qth.net>
Sent: Sunday, September 07, 2008 11:51 AM
Subject: RE: [Elecraft] K-3 Contest agc settings
If you are a contester please respond off list.
I chose to reply to the list because this is a topic of interest to many,
whether contesting or not.
What AGC
settings are you using? In sprint last night I used the K-3
(first real contest) and I was less than thrilled with rx
performance. Close by stations seemed to overload the rx.
Something I didnt have with my MKV with the inrad mods and
filters. Been fiddling with the settings but obviously dont
have it right.
All my operating is contesting and I've used two K3s for a year now. At
home, there are several local contesters just a few miles line-of-sight
off
the back lobes of my Yagis. At 1.5 KW they saturate my S-meters. Still,
they are unnoticeable when outside my filters and I'm usually run the
default AGC settings. Most people have reported just the opposite
comparison between the MKV and K3, i.e., they prefer the K3 RX in contest
or
crowded band conditions with strong signals nearby.
The PREamp has more impact on RX overload than the AGC in most cases. On
the low bands, you may even need to engage the ATTenuator. Don't make the
AGC do all the work by slamming it with too much signal strength.
Certainly, you can optimize the AGC for different conditions by changing
the
threshold and slope. For many it is a matter of personal preference more
than an absolute "correct" setting. You will probably want higher
thresholds on the lower bands due to the noise level. The slope is a
trade-off between reducing gain for strong signals and still having
discrimination between different signal strengths. If you keep the
front-end tamed down with appropriate PRE and ATT engagements, then you
will
find the AGC gives you fine control over the range of signal strengths
rather than relying on it alone for dealing with the very strong signals.
filters in rig 2.8, 1.8 and 250
Remember your "250" filter is really 370 Hz at the -6 dB points, so you
might have it engage at DSP bandwidth of 350 or 300 Hz. But even at 350,
the cascade effect will produce an overall bandwidth of less than 300 Hz,
which is a bit narrow for CW contesting, IMO. At DSP WIDTHs of 400-500
Hz,
your roofing filter will be the 1.8 kHz, if you have it configured
"normally", so that doesn't give you IMD protection for the DSP with very
strong signals located between your DSP and crystal filter widths.
(I should point out that some K3 ops don't subscribe to the K3 design that
deploys the crystal filters as roofing filters that are set wider than the
DSP WIDTHs to protect the DSP. Instead they prefer the passband shape of
the crystal filter and effectively eliminate the DSP filter by configuring
their K3 filtering to have the crystal filter engage at DSP bandwidths
GREATER than the crystal filter. Until the DSP WIDTH is reduced to well
within the crystal filter bandwidth, the crystal filter is dominating the
passband shape and filtering. Of course, the DSP will still provide
steeper
skirts at a point well below the passband.)
73,
Ed - W0YK
P.S. Thanks for the Sprint Qs!
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