[Amps] Drifting Power

[Bruce Campbell]

I have noticed that many amplifiers are designed to be most efficient 
_NOT_ at room temperatures, but a bit above room temp. A good compromise 
in design. I have noticed this is both tube and solid state amps. I do 
not have your amplifier in front of me, rather I am speaking in general.

73, Bruce, W8HW

=========================================

On 10/16/2021 10:32 AM, Pete Smith N4ZR wrote:
> FWIW, I see something very similar in my KPA-1500.  I had assumed it 
> was software protecting the transistors, just in case.
>
> 73, Pete N4ZR
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>
> On 10/16/2021 10:05 AM, Steve London wrote:
>>   I have a Commander HF-2500 Magnum, with a pair of 3CPX800's. Great 
>> amp.
>>
>> It has one quirk, and only on 15 meters. If the amp has been dormant 
>> for a
>> while, the output power is initially low: about 1100 watts. Key down it
>> gradually rises up to 1500 watts over about 10 seconds. After that, if I
>> intermittently transmit, at least every 5 minutes, it will stay at 1500
>> watts. Only after being idle for ~30 minutes will it go back to the low
>> output state.
>>
>> My thought is that something in the input pi network is heating up.
>> However, I have accurate SWR/power meters on both the amp input and amp
>> output. Neither the input power nor SWR is changing as the output power
>> rises. As the power rises, the grid current drops, but the plate 
>> current is
>> unchanged. Again, this is only on 15 meters.
>>
>> Suggestions ?
>> 73,
>> Steve, N2IC
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