[Elecraft] ALC and External Power Amplifiers (K2)

[VR2BrettGraham]

K2VCO replied to AB2PN's post:

>There isn't one, but it would be useful.  Although activation of ALC on
>a regular basis is not a good idea (since it has a finite attack time,
>it can't prevent driving an amplifier into nonlinearity, at least for
>short periods), it can function as a safety feature.  For example I've
>just installed an Alpha 86.  It produces 1 KW output with about 35 watts
>of drive (I haven't dared to run the full 1500 watts for fear of
>damaging antenna components, etc.).  I can only shudder to think about
>what might happen if I forgot to turn down the power control on my K2
>and hit it with 100 watts!

My Ten-Tec 420E & a recently acquired ACOM 1k have on a number of
occasions indicated they did not appreciate what appeared to be far greater
drive (based on number of light bulbs on K2/100: all) than I would expect
based on position of the POWER control (anti-clockwise 50% or greater) for
short instances.

I normally observe variations in output level to be of lower-to-higher power,
such as for the first few key-down elements after a band change (good idea,
Elecraft!).

Wasn't there a post by somebody recently that suggested the power level
steps when the KPA100 kicks in might be better if it weren't so granular,
followed by a reply from Elecraft that something might be done about it at
some point?

Thankfully, my 8877 amp has so many problems I can't use it, but I'd be a
little concerned with the overshoot mentioned above (perhaps a fault with my
particular K2/100?) or dithering of the drive that I often see due to the
granularity should one operate such a sensitive tube close to its limits.

That amp (DTR-2000) was probably the worst 8877 implementation, but
thankfully most everything else has reasonable protection.

73, VR2BrettGraham