[Elecraft] APF and audio limiting

Sat Nov 6 22:07:41 EDT 2010

I think you're the one who is out of line, Mr. Smith...Joe is being
accurate; you're not.  If you're going to try to help someone, then give
them accurate information...not information that is "sort of" correct...and
then complain when someone does correct the information.  I learn a lot from
Joe's posts and appreciate that he is a knowledgeable guy who is willing to
share with the group.  73 de Greg-N4CC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of The Smiths
Sent: Saturday, November 06, 2010 7:13 PM
To: lists at subich.com; Elecraft Reflector
Subject: Re: [Elecraft] APF and audio limiting

If I said black you would say white.  What's the difference.  Fine, it's not
bringing the level UP to the AF Output, it's setting it TO the AF output
according to the slope setting.. Unless of course the manual is written
improperly too. Stop being such a nit pick Joe, you don't ALWAYS have to
correct everyone..  My point is still the same.  He heard the loud signal
LOUD because that's where his AF Output was set to.
Perhaps you can spend more time helping this person than knocking down those
that DO try to help others.  It would be time better spent. END OF.

Sorry Eric, but I just feel like Joe is out here like a shark circling
around looking for someone to bite.

> Date: Sat, 6 Nov 2010 20:48:14 -0400
> From: lists at subich.com
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] APF and audio limiting
> 
> 
> >> Remember, the AGC is only supposed to bring things to the level of 
> >> your AF output setting.
> 
> No. AGC should never "bring up" the level. AGC *REDUCES* the level of 
> signals above the AGC threshold. One normally sets the audio level for 
> signals *at the AGC threshold* or below and AGC keeps stronger signals 
> from exceeding that level (by the amount of the "slope" if one is not 
> using a "hard" threshold).
> 
> The difference with an *AUDIO PEAK FILTER* is that the APF is in the 
> AUDIO circuit *AFTER* the detector and *OUTSIDE* the AGC loop. Since 
> the PEAK gain of the K3 APF is roughly 10 dB - see the response here:
> http://n1eu.com/K3/K3_apf.htm - this can cause an issue with strong 
> signal but is a big advantage with signals at or near the noise level 
> (and below the AGC threshold). Of course, the gain is exactly why APF 
> can be turned on and off ... you don't want it on with strong signals 
> - only with those at the noise signals where it makes a difference!
> 
> 73,
> 
> ... Joe, W4TV
> 
> 
> On 11/6/2010 8:20 PM, The Smiths wrote:
> >
> > I think that your understanding of the AGC is probably pretty good. I
also think that most people don't know how to set their AGC properly. Yes,
there should have been SOME control over the loudness of the other signal,
but because the Peak filter brings everything up as it does it can also take
an S9 signal and make it sound like an S40 over signal too, even when the
AGC is compressing things..
> >
> > Remember, the AGC is only supposed to bring things to the level of your
AF output setting. Therefore if you have your AF all the way up, well,
that's as loud as the AGC will put it under Sloping conditions.. It doesn't
mean that EVERY weak signal will also be within your AGC Threshold. What
"sounds loud" because of the APF is on doesn't mean that it's opening your
threshold control in the AGC. There in lies your problem I think.. What you
thought was under AGC control, really wasn't!. What you were actually
hearing is proper Dynamic range you should have. So the volume control still
comes into play.
> >
> > I'll send you a copy of my AGC tutorial offline. I hope this helps you
out some.
> >
> >
> >> Date: Sat, 6 Nov 2010 19:46:11 -0400
> >> From: nf4l at nf4l.com
> >> To: elecraft at mailman.qth.net
> >> Subject: Re: [Elecraft] APF and audio limiting
> >>
> >> Thanks Tom.
> >>
> >> Well, I kinda thought it shouldn't blast my ears that hard. Audio 
> >> *WASN'T* up too loud for the signal I was after. Maybe I don't 
> >> understand what AGC does. That's why I asked the questions I did.
> >>
> >> On 11/6/2010 6:21 PM, Amateur Radio Operator N5GE wrote:
> >>> On Sat, 06 Nov 2010 18:04:18 -0400, Mike<nf4l at nf4l.com> wrote:
> >>>
> >>> Sounds normal to me.
> >>>
> >>> Audio up too loud and APF on, then a strong signal transmits on 
> >>> the frequency you are listening to....
> >>>
> >>> What do you think it SHOULD have done? You didn't say.
> >>>
> >>> Tom
> >>> Radio Amateur N5GE
> >>>
> >>>> On 11/4/2010 9:48 PM, Mike wrote:
> >>>>> I'm playing with the new APF, and trying to get a REALLY weak 
> >>>>> QSO to pop. I have the volume cranked up pretty good, and a 
> >>>>> REALLY strong station throws in their call. I thought my speakers
had blown. Glad I wasn't wearing cans.
> >>>>>
> >>>>> My CONFIG:AF is 18, AGC = F.
> >>>>>
> >>>>> Was I doing something wrong? Anybody else experience this? Do we 
> >>>>> need/can we have better audio limiting?
> >>>>>
> >>>>> 73, Mike NF4L
> >>>
> >>
> >>
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