[Elecraft] [ELECRAFT] KPA500 NEW OWNER QUESTIONS.......

[Don Wilhelm]

In this discussion about ALC, I have to inject a bit of fact.
The Elecraft transceivers K2/K3/K3S/KX2/KX3 use a power control system 
that is different from all other amateur transceivers, and unless there 
is a problem with the transceiver, there is no power overshoot.  In 
fact, after a band change or a power setting change, the RF starts at a 
low level and builds up to the power knob setting after a dit time or a 
few syllables on voice.

That means amplifier ALC is not necessary, and if used should never be 
used for power level control (doing that will cause distortion).

W8JI - Tom Rauch is responding to operation with most transceivers 
driving the amplifier.  With the Elecraft transceivers, the amplifier's 
ALC indicator should never come on unless there is an amplifier fault 
condition - high SWR, no antenna, etc.
Tom W8JI should know - he designed several of the Ameritron amplifiers.

Operated properly, there is no need for ALC at all, especially with 
those amplifiers employing cathode or grid detection of overload.  For 
the amplifiers with more sophisticated fault detection, connecting the 
ALC line to the driving transceiver is OK because it allows the 
amplifier to shut down (or reduce power) the transceiver if a fault is 
detected.

As Tom pointed out in at the end of his article, ALC should not be used 
as a power control mechanism - doing so will only lead to distortion.

73,
Don W3FPR

On 2/28/2019 10:19 PM, Bob McGraw K4TAX wrote:
> This fellow seems to have a good handle on the ALC issue as it relates 
> to overshoot in the transceiver.
> 
> https://www.w8ji.com/alc_exciter_power_overshoot.htm
> 
> 
> Here Tom goes into the discussion of good ALC vs. bad ALC systems.
> 
> https://www.w8ji.com/ameritron_alc_adjustment.htm