Joe,
Thanks for the very thoughtful analysis.
I'm very pleased to say that the problem seems to be greatly reduced with
the latest firmware (1.81/1.63). I can't tell if it is completely
eliminated, but it's certainly much reduced. Lyle, Wayne, what did you do?
Whatever it is, it seems to have helped greatly.
73, andy, ae6y
----- Original Message -----
From: "Joe Subich, W4TV" <[EMAIL PROTECTED]>
To: "'Andy Faber'" <[EMAIL PROTECTED]>; "'wayne burdick'"
<[EMAIL PROTECTED]>
Cc: <[email protected]>
Sent: Sunday, April 13, 2008 6:56 PM
Subject: RE: [Elecraft] Audio problem in WPX SSB
Andy,
Here is what happens: For phone contesting, I my software
CQPWIN, which plays wav files for DVK usage (as do other
programs). I run the output in such a way that when the dvk
is playing, the mic is shut off, but the audio from the computer
goes into the mic connector of the radio. As soon as it stops
playing, it disconnects the computer and reconnects the
microphone. I run it from the computer into a W2IHY iBox for
isolation, and the output to the radio. The Mic is a Heil
pro-set.
> With the K3, the messages play fine, but after one finishes,
if I use the mic, the radio starts out at lower power and takes
2-4 seconds to build back up to high power. This is the same
whether using the front or rear input and whether using high or
low gain.
After working in this quite a bit over the weekend the problem
is related to the K3 "microphone AGC." It appears that levels
from the microphone and DVK must be extremely well balanced -
much more closely balanced than with any other radio or the
stronger input will cause the microphone AGC to reduce the
mic gain and the weaker input will be much weaker. The 2-4
second delay seems to be related to an extremely long ACG time
constant (probably intended to prevent the ACG from acting like
a clipper).
The problem is made worse - at least in my case - because the
ALC indicator provides only 5 very small, difficult to see,
bars for adjustment and the "steps" are rather course (6 dB
per division). This means that the maximum "spread" between
the two inputs can be almost 12 dB (!) even when the display
only shows a slight flicker between the two adjacent bars
(e.g., the mic is barely triggering the 5th bar and the DVK
is hitting the sixth bar "hard").
After some thought there are several ways (a combination of
all is best) to help the situation:
1) reduce the time constant (AGC "hang") to about .5 second
and "dump" any gain reduction when the PTT is released.
2) Use more of the "ALC" display to get better resolution.
There are 12 "bars" in that part of the display but only
six are used (with the sixth indicating overdrive). At
least expand the "good" range to seven (or eight) bars
to coincide with the right edge of the ALC bracket.
3) Make the ALC display response logarithmic (like a VU
meter). Instead of 5 x 6 dB or 30 dB total ... the same
total range could be displayed with the first bar = -20 dB,
the second = -10 dB, the third = -7 dB, the fourth = -5 dB,
the fifth = -3 dB, the sixth -1 dB, the seventh = "0 dB",
the eighth +1 dB, the ninth +3 dB and the 10th +6 dB.
Setting/matching levels would be MUCH easier. It's no
accident that professional recording and broadcasting have
used similar scales for decades.
4) Give the ALC meter a dual mode display - showing both short
duration "peak" and average (the current ALC) would help.
Alternatively, any "peak hold" dot above the ALC region
could show gain reduction by the mic AGC (and warn about
overdriving the input).
5) Provide a "set-up mode" that disables mic AGC - this
will allow balancing sources (either FP/RP/Line or
multiple inputs on an external mixer) without chasing
the effects of the mic AGC.
I understand there has been some work on the mic AGC in the
firmware currently in test and that may help. However, this
area needs to be more "user friendly." As it is, I can see
significant issues when using the K3 in a multi-operator
setting where the relative levels need to be reset completely
for every operator change!
73,
... Joe, W4TV
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Andy Faber
Sent: Monday, April 07, 2008 12:08 AM
To: [EMAIL PROTECTED]; wayne burdick
Cc: [email protected]
Subject: [Elecraft] Audio problem in WPX SSB
Wayne,
A peculiar audio situation arose using my K3 in Aruba in
WPX SSB. It
works the same way at home, and isn't a problem I've ever had
with any of
many other radios that I've used in the same contest configuration.
Here is what happens: For phone contesting, I my software
CQPWIN, which
plays wav files for DVK usage (as do other programs). I run
the output in
such a way that when the dvk is playing, the mic is shut off,
but the audio
from the computer goes into the mic connector of the radio.
As soon as it
stops playing, it disconnects the computer and reconnects the
microphone.
I run it from the computer into a W2IHY iBox for isolation,
and the output
to the radio. The Mic is a Heil pro-set.
With the K3, the messages play fine, but after one
finishes, if I use the
mic, the radio starts out at lower power and takes 2-4
seconds to build back
up to high power. This is the same whether using the front
or rear input
and whether using high or low gain. Also, the W2IHY box has
to be turned up
to a level that normally would overdrive other radios.
I tried not using the W2IHY box (ie, running the audio
straight from
either my laptop or my desktop to the radio) with the same
result. It also
doesn't matter if the radio is using PTT or VOX, or whether
it just remains
in transmit.
These seems like a some kind of odd impedance issue, but,
as I said, it's
one that has never shown up with Icom-Yaesu or Kenwood radios.
Any ideas? I'm using 1.78/1.58 firmware, and the radio was
just back to
you for Rene to do hardware mods (serial number 76). In all
other respects,
I loved it in the contest.
73, Andy, AE6Y
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