>
>2 Wrote:
>
>>// Do two equal-capacitance paralleled caps have a resonance?
>>
>They do not develop a new parallel resonance due to being connected
>together.
>
\ This does not appear to be the result when one experimentally
parallels two, equal value doorknob caps with straps and checks for
resonance with a dipmeter.
>>And later:
>>// In my experiences 50, 57, and 58 Series doorknob caps have a
>>resonance at VHF or UHF. A 0.01uF disc ceramic cap resonates c. 10MHz.
>>
>Certainly - these are all *series* resonances with their self-inductance
>(plus the inductance of the wire you used to "short" the cap for
>dipping).
>
>>// Mr. Rauch stated that the dipmeter adapter does not work correctly.
>>
>I seem to remember he said that MFJ marketed it against his advice
\ semi-agreed
>- but the MFJ analyzer manuals do give details of the methods I suggested,
>which are superior to dipping.
>
\ Certainly - for finding the series resonance of a single capacitor.
This number is important to know since a bypass-C behaves like the
desired capacitive reactance only below the series resonant freq. Above
this point, it looks inductive. This is why a tetrode-with-handles
cathode/fil. needs bypasses using different capacitance values. As I
recall, I used 4, 1000pF; 4, 3300pF; 4, 4700pF; and 4, 6800pF -- rated
at3kV.
>
>>>lMost modern CF/MO resistors have a spiral element, but if you scrape off
>>>the paint, measure the diameter and length, and count the turns, you can
>>>estimate the inductance using the normal coil formula. You'll find that
>>>at low impedance levels the inductance is generally too small to matter
>>>below 30MHz.
>>>
>>// ... which is about as useful as teats on a boar.
>>
>I bow to your obviously extensive knowledge of porcine anatomy... but
>not to your engineering judgement.
>
\ Touché. However, the resonance of two, strapped, 58-series doorknob
caps is not below 30MHz. As I see it, the resonance of two, paralleled
DC blocking caps is not often a problem -- although it can be. I know
of a 2, 4-1000A/8166 amplifier where it was.
>
cheerio, Ian
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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