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

[Bob McGraw K4TAX]

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


73
Bob, K4TAX



On 2/28/2019 8:51 PM, K9MA wrote:
> Many years ago, I built a tube amplifier with what I thought was a 
> fairly sophisticated ALC circuit. I could never get the ALC loop to be 
> stable. I know a lot more about control systems now, but I still don't 
> know how to get ALC around an amplifier to work, and apparently 
> neither does anyone else. What I don't understand is why it's so hard 
> with an external amplifier, as every transmitter has ALC for its 
> internal 100 W amplifier, and that works fine. Why the same design 
> doesn't work with an external amplifier is the mystery.
>
> The problem with just limiting the drive power and using the 
> transmitter's ALC is that, especially for solid state amplifiers, the 
> required drive power can vary considerably with SWR and temperature.  
> That requires either riding the power control continuously or running 
> your amplifier well below rated output most of the time. (Unless, of 
> course, you're running a 2.5 kW amplifier, but that kind of margin is 
> expensive.) So, if anyone could figure out how to get ALC to really 
> work with an amplifier, I think that would be worth paying extra for.
>
> 73,
> Scott K9MA
>