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

[Lyle Johnson]

Answers interspersed to reduce confusion from top posting.
>
> The K3's AF Limiter is a HARD limiter that has an abrupt onset
> and causes extreme distortion. 

Precisely. It's sole purpose is to PROTECT your ears, not help you copy 
weak signals in the midst of strong ones.

> ...
> 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.

Correct. Note that *any* kind of limiter is going to cause huge IMD 
issues if multiple signals are present, and it is exactly this condition 
that is a primary driver for people not using AGC, at least in the 
context of this thread.  Using AGC is much better than any kind of 
limiter if the intent is to still copy the weak signal in the presence 
of the strong one.  The only solution is to reduce gain and get things 
linear again.

You have to turn the knob CCW :-)

> 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.

The Fuzz (harmonic distortion on a single signal) or IMD (if multiple 
signals) is the condition that is the problem in the first place.  Any 
limiter is nonlinear and will produce IMD.

The extreme IMD from the hard limiter is telling you to back off the 
gain until things get linear again.
73,

Lyle KK7P