>
>
>
>----------
>>
>>
>>
>> >
>> >> >Just as a ball park reference, in my hand is a 258 pF 8KV 7A @ 3mHz. It
>> >> >measures 3X3X2 1/4 inches.
>> >> >
>> >> ? As I understand it, the current handling ability of mica caps
>> >> decreases above 3MHz.
>> >
>
>Depends on the cap. At a quick glance, the curves in the CDE
>Transmitting Mica Data book indicate that peak current handling occurs
>NEAR 1 Mhz. Closer inspection shows that this is true mainly for the
>larger sizes such as 5000 pf and up (this is a reasonable generalization,
>but it does change for different models). For the under 5000 pf sizes
>(again, in general), the current handling either increases steadily with
>frequency up to around 30 Mhz, or it max's. out somewhere between 3 and 10
>Mhz and stays more or less flat up to 30 Mhz. In most cases, the current
>rating is several times what any of us are likely to expose them to.
>
>CDE also tabulates the current data at 0.1, 0.3, 1 and 3 Mhz. The tabular
>data alone would suggest that max current handling occurs at 3 Mhz with
>many of the models, and this perhaps is the data behind Rich's comment.
>The curves tell a more complete story.
>
>Separately, I was impressed with the current handling capabilities of the
>type CDV16 dipped mica caps. Fairly small in size, some of these will
>handle 6 or more amps of RF - perfect for input matching networks.
>
>
thanks for the information, Phil. .
>
>
>> >> Rich...
>> >
>> >Not according to the data I see in about a half dozen places.
>>
>> ? got any URLs, Tom?
>>
>> > Many mica capacitors continue to increase in current with frequency,
>> >depending on the style of construction and value, way up into VHF.
>> >
>> >Multi-layer micas are a very common high current VHF capacitors.
>>
>> ? I never saw a mica capacitor that wasn't multi-layer.
>> >
>> >Mica does not become a poor dielectric at 3 GHz, let alone 3 MHz.
>>
>> ? Who said that it becomes a poor dielectric at 3MHz? In my collection
>> of mica transmitting caps, current rating is often speced at a few MHz
>> and/or a few hundreds of kHz. The info on derating mica above 3MHz came
>> from Lenk at Hiway Sales in Oceanside, California.
>>
>> > .
>> >Especially Ruby Mica, which is used in some of the lowest ESR
>> >capacitors available for microwave.
>>
>> ? Impressive. So why isn't ruby mica dielectric used in HV caps. for
>> HF amps.?
>>
>> - cheers, Tom
>>
>>
>> Rich...
>>
>> R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
>>
>>
>> --
>> FAQ on WWW: http://www.contesting.com/ampfaq.html
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>>
>>
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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