[Elecraft] AF Limiter (was Recommended AGC settings for separation of signalsin CW pile-ups)

[Dave Hachadorian]

Hi Lyle,

Thanks for entering the discussion. It's great that the company
guys monitor these reflectors.

Even at its maximum 030 setting, the AF Limiter is problematic.

The K3's AF Limiter is a HARD limiter that has an abrupt onset
and causes extreme distortion.  In fact, once the AF Limiter
threshold has been hit, the louder the signal is, the less audio
comes out of the headphone amp, at least as measured on my DVM.
Once the limiter is hit, there is absolutely no hope of pulling a
signal out of the pileup.  One absolutely must reduce AF or RF
gain to pull anything out at that point.

A soft limiter on the other hand (such as a pair of back-to-back
Schottky Diodes) doesn't cause that extreme distortion, and
allows a much wider usable dynamic range, albeit with some minor
fuzz on very loud signals.

There is no way, despite K3NA's excellent attempt
http://wiki.contesting.com/index.php/Setting_receiver_gain_controls
to set the K3's RF and AF gain controls to accommodate the
dynamic range of signals encountered on the bands, without riding
the RF and/or AF gain controls.  Maybe it is possible with
super-sensitive headphones, but not with any that I have tried.

The most successful method of dealing with pileups that I have
found (other than agc OFF, and constantly riding the RF gain) is
to use an external audio amp with a soft limiter.

I wonder if there is a place in the K3 to put a pair of limiting
diodes, ahead of the AF Limiter?

Dave Hachadorian, K6LL
Yuma, AZ





-----Original Message----- 
From: lyle johnson
Sent: Sunday, December 05, 2010 11:18 AM
To: Elecraft Reflector
Subject: [Elecraft] AF Limiter (was Recommended AGC settings for
separation of signalsin CW pile-ups)

The AF Limiter in the K3 is designed to allow you to
protect your hearing when you have the AGC off and gain
cranked up to hear the signal buried in the noise just as
your neighbor with his beam bore-sighted on your QTH and
running the Alpha amplifier starts transmitting on that
same frequency.

Note that the AF Limiter level is completely adjustable
when AGC is OFF.  At its highest setting it clips just at
the threshold that the audio amplifiers in the K3
otherwise limit/clip.

In fact, when AGC is ON, the AF Limiter is still present
but set to this highest level.

So, if it bothers you, please set it higher :-)

Enjoy!

73,

Lyle KK7P (at 38,000 feet enjoying in-flight WiFi)
> you have to deal with the crazy AF Limiter.
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