>R. Measures wrote:
>
>>
>>>lou de beer wrote:
>>>
>>>
>>>>Anyone own an Alpha 86...I have a question regarding the bandswitch.....
>>>
>>>I just replaced a bandswitch wafer on one. ...
>>
>>
>> *** Vic -- I would like to buy the old bandswitch wafer from you if you
>> are willing to part with it. I am also looking for kaput 3cx800A7s. tnx
>> - If anyone else has some of these items, please name your price.
>
>I will be happy to send it to you at no charge, Rich.
** Tnx, Vic.
>I think the
>question "why did this burn out" is interesting, because I know the
>individual who was operating it when it happened, and he did not
>hot-switch it. He was attempting to load an 80-meter coax-fed dipole on
>160 meters (it was late, in a contest, etc.). The contacts which burned
>were used to switch padders in parallel with the loading capacitor of
>the Pi-L output circuit.
** But how did the 160m Load-C padder contacts arc if they were closed?
>
>The question then is, "Why didn't the amplifier trip off from excessive
>SWR?" My theory, which I will happily hear attacked or supported, is
>the following:
>
>The amp doesn't exactly trip on SWR, it trips on reflected power. My
>sleepy friend found a setting of the controls which was highly
>underloaded, producing a very high circulating current in the tank
>circuit, and very little power out (and hence very little reflected
>power). The current was enough to burn the contacts.
** The contacts burned while closed?
>He probably was
>not driving it very hard, or it would have tripped on grid current.
** Was he using an antenna tuner to match the few-ohm antenna to the
50-ohm amplifier??
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