[Elecraft] ALC Setting was (Audio problem in WPX SSB)

[Brett Howard]

I agree that corresponding with the end of the ALC bracket makes sense.
I remember looking at the pictures of the radio after it was mentioned
that the 6th bar was overdrive and I was thinking it odd that the
overdrive point didn't correspond to the end of the ALC brackets.  My
Kenwood has a line that tells one where the ALC kicks in.  It just seems
like that type of operation makes intuitive sense where as the 5 bars
thing is something that one would have to read the manual/reflector to
know.  

On Sun, 2008-04-13 at 21:56 -0400, Joe Subich, W4TV wrote:
> 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: elecraft-bounces at mailman.qth.net 
> > [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Andy Faber
> > Sent: Monday, April 07, 2008 12:08 AM
> > To: nextk at elecraft.com; wayne burdick
> > Cc: elecraft at mailman.qth.net
> > 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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