>
>on 11/3/99 16:45, measures at measures@vcnet.com wrote:
>
>>> WHY? Why would a rheostat stop doing what a rheostat is supposed to do???
>>>
>> ? Hang onto your hat. The nichrome resistance wire that the rheostat
>> was made from was subject to disintegration from atmospheric effects.
>> The graphite contact in the movable arm would crumble. The carbon
>> contact in the movable arm would wear away quickly.
>
>So according to these "experts" a rheostat is not capable of varying the
>magnitude of an AC voltage.
... not what they said.
>Go figure. Hey, I have a rheostat on my
>filament AND on my HV primary.
>
A rheostat in the HV transformer primary is bananas.
>>>
>>>> One should keep in mind that above its self-resonant frequency, a
>>>> capacitor looks like an inductor. For example, your typical 0.01uF
>>>> disc-ceramic universal "bypass" capacitor looks like an inductor on 20m -
>>>> 10m.
>>>
>>> I agree with your comment. I am surprised though that the caps are that
poor.
>>
>> The caps were not poor.
>
>Poor is a relative term. I mean poor RF performance. Looking like an
>inductor at 14 MHz may be what is supposed to happen with that cap, but it
>is still "poor" RF performance.
I disagree.
>>
>>> I know even most "quality RF" caps
>>
>> Even Quality cap leads have inductance.
>
>Oh agreed, agreed. But then that can be minimized by shortening the leads
>as much as possible. So is the poor 14 MHz performance due to longer leads
>than should be used (sometimes you have no choice) or is the performance due
>to the way the cap is internally constructed? I'm not disbelieving what you
>measured, I am just trying to get a handle on the HF performance of a
>typical disc capacitor.
>>
You gotta short the cap with wide Cu foil and measure the resonance with
a dipmeter..
cheers, Jon
- Rich..., 805.386.3734, www.vcnet.com/measures.
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