[Elecraft] SSB Overshoot

[Don Wilhelm]

Jack,

Those displays look quite similar to what I would have expected - overshoot
will occur if the audio is increased sufficiently to activate the ALC.

The displays do point out the necessity of not driving the K2 into ALC if
overshoot is to be avoided - for digital modes, that means to increase the
requested power to well above the intended operating power and limit the
drive using the mic input level.

Of course, the same thing applies to most any other transceiver if the IMD
is to be kept at a minimum - the thing unique about the K2 is that the
control of the power output level is also involved.

I always have bad feelings about attempts to use ALC as a power output
limit - expecially on SSB because it only leads to distortion.  It is a form
of compression, but audio compression is much better at increasing the
average power of a signal.  One could design a compressor that works at RF,
but it would be quite different than the ALC found in most transceivers.

73,
Don W3FPR

> -----Original Message-----
>
> I've made a quick series of measurements at 7 MHz, 50 watts output and
> varying audio drive levels and posted the result in a PDF file that may
> be viewed at
> http://www.cliftonlaboratories.com/Documents/SSB%20Burst%20Analysi
> s%20Elecraft%20K2.pdf
>
> Jack K8ZOA
> K2: 5689
> www.cliftonlaboratories.com
>