[AMPS] ameritron al-82

[Pete Smith]

At 12:10 PM 2/15/2000 -0700, measures wrote:
>>
>>At 07:43 AM 2/15/2000 -0700, measures wrote:
>>>€  However, when the 20m tap on a SB-220 is used for 30m operation, the 
>>>operating Q and the circulating current in the tank increases by c. 40%.  
>>> This causes a doubling of the  I-squared x R heating in the bandswitch 
>>>contacts.  Using the CW tap would help a bit, however, I would not take 
>>>the risk.  220 bandswitches are no longer manufactured.  
>>
>>On the other hand, if he holds it to the legal 200W power for 30m, the
>>I-squared part will be pretty small, and the risk probably commensurate.
>>
>Decreasing drive and anode current to reduce P-out does not reduce the 
>voltage swing across C-Tune --  if the amplifier is  normally tuned for a 
>peak in output.   Thus, the AC voltage across C-tune is not decreased by 
>reducing P.  (The AC potential across C-tune is the major determiner of 
>tank circulating current -- and this is controlled by the anode supply 
>potential.)  .  

Oh?  So reducing plate current by a factor of 4 doesn't reduce Isquared-R
heating of the bandswitch by a factor of 16, as I'd expect?  Seems
counterintuitive, but I'll take your word for it unless others beg to differ.

73,  Pete N4ZR

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