K2 ALC action

[W6IZT]

 
I am seeing an ALC action from my K2 that I don't understand
 
When I key my amp (Command Tech HF2500) with my K2 (sn 3188 all mods  
performed) I see the grid current on the amp cycling between 3 distict  steps.
 
For example:
 
-When I first key the radio with a continuous carries the amp will show 30  
ma of grid current, increasing to 40 ma over the next second or so.
-The grid current will then immediately drop to 20ma and increase to approx  
28 ma over the next second or or so
-This repeats one more time.
 
I also see this when sending a continuous string of dits
 
The input VSWR to the amp is 1.3:1
 
I do not see this effect with any other radio
 
I'd liek to understand why this effect is happening and how it can be  
eliminated. Any help is greatly appriciates
 
73
Gregg
W6IZT

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[Don Wilhelm-3]

Gregg,

Try the K2 optional power control mod
http://www.elecraft.com/Apps/Power_Control_Mod.html and see if that helps
your power fluctuation.  Even if it isn't a complete cure, it will minimize
the fluctuation.

The K2 does its ALC through the microprocessor and changes the power in
discrete steps through a DAC - and you are seeing the K2s attempt to keep
the power at the level requested on the power control pot.  Many other
transceivers use analog controls to vary the output and the steps are not
present.

73,
Don W3FPR

> -----Original Message-----
>
> I am seeing an ALC action from my K2 that I don't understand
>
> When I key my amp (Command Tech HF2500) with my K2 (sn 3188 all mods
> performed) I see the grid current on the amp cycling between 3
> distict  steps.
>
> For example:
>
> -When I first key the radio with a continuous carries the amp
> will show 30
> ma of grid current, increasing to 40 ma over the next second or so.
> -The grid current will then immediately drop to 20ma and increase
> to approx
> 28 ma over the next second or or so
> -This repeats one more time.
>
> I also see this when sending a continuous string of dits
>
> The input VSWR to the amp is 1.3:1
>
> I do not see this effect with any other radio
>
> I'd liek to understand why this effect is happening and how it can be
> eliminated. Any help is greatly appriciates
>
> 73
> Gregg
> W6IZT
>

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