[Milsurplus] When is a Cap Not a Cap? Redux

[Ian Wilson]

:)


On Tue, Sep 17, 2013 at 5:14 PM, Peter Gottlieb <nerd at verizon.net> wrote:

> Yeah, a LEC.
>
>
>
> On 9/17/2013 8:13 PM, Bob Camp wrote:
>
>> Hi
>>
>> …. and shortly after the cap cracks into several pieces ….
>>
>> Bob
>>
>> On Sep 17, 2013, at 8:05 PM, Peter Gottlieb <nerd at verizon.net> wrote:
>>
>>  When a cap turns orange that's resistive loss and then the phase angle
>>> does match and then energy goes into the cap.
>>>
>>>
>>> On 9/17/2013 7:57 PM, Bob Camp wrote:
>>>
>>>> Hi
>>>>
>>>> A cap designed to handle RF power is normally rated in terms of KVAR
>>>> (kilovolt amperes reactive if I remember correctly). Strictly speaking it's
>>>> not power, but energy. The phase angle (current to voltage) is wrong for it
>>>> to be power.
>>>>
>>>> Simple approach is to strap a current probe on the beast and see how
>>>> much current there is. For a big cap, that's going to be a healthy probe.
>>>>
>>>> Does it matter - well yes indeed it does. I've seen caps light up a
>>>> nice bright orange (briefly) when things have gone wrong and the current is
>>>> a tad high…
>>>>
>>>> The issue is obviously the loss (angle really isn't 90 degrees) in the
>>>> cap. For small value caps (like a normal silver mica) you can measure the
>>>> loss and figure out what's going on. The CK45 series cap mentioned isn't
>>>> intended for high power RF use, so I'd bet it's pretty nasty compared to a
>>>> normal COG / NPO part.
>>>>
>>>> Bob
>>>>
>>>> On Sep 17, 2013, at 9:35 AM, C.Whitaker <whitaker at pa.net> wrote:
>>>>
>>>>  de WB2CPN
>>>>> So how does one measure the RF power going through a capacitor?
>>>>> What are the parameters?
>>>>> 73  Clete
>>>>> ++++++++++++++++++++++++++++++**+++++++++++++++++++++
>>>>>
>>>>> On 9/17/2013 7:19 AM, David Stinson wrote:
>>>>>
>>>>>> Some time ago, we had a discussion about "when is 150 pFd NOT 150
>>>>>> pFd."
>>>>>> I had purchased some 100 and 150 pFd ceramics to us in a
>>>>>> series-resonant LC circuit
>>>>>> carrying about 10 watts of RF to an antenna.
>>>>>> I believe it was this cap:
>>>>>> http://www.digikey.com/**product-detail/en/CK45-**
>>>>>> R3AD151K-NR/445-2715-ND/**1007601<http://www.digikey.com/product-detail/en/CK45-R3AD151K-NR/445-2715-ND/1007601>
>>>>>> While 150 pFd silver micas from my junk box worked fine,
>>>>>> these brand-new ceramics disappated more than half the power
>>>>>> I sent through them.  The whole bunch was worthless for this
>>>>>> application.
>>>>>>
>>>>>> I wanted to review that thread, but can't find it.
>>>>>> Are there any thoughts on why this is the case,
>>>>>> and how I might avoid this mistake in the future?
>>>>>> ______________________________**______________________________**__
>>>>>> Milsurplus mailing list
>>>>>> Home: http://mailman.qth.net/**mailman/listinfo/milsurplus<http://mailman.qth.net/mailman/listinfo/milsurplus>
>>>>>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>>>>>> Post: mailto:Milsurplus at mailman.qth.**net<Milsurplus at mailman.qth.net>
>>>>>>
>>>>>> This list hosted by: http://www.qsl.net
>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>
>>>>>>  ______________________________**______________________________**__
>>>>> Milsurplus mailing list
>>>>> Home: http://mailman.qth.net/**mailman/listinfo/milsurplus<http://mailman.qth.net/mailman/listinfo/milsurplus>
>>>>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>>>>> Post: mailto:Milsurplus at mailman.qth.**net <Milsurplus at mailman.qth.net>
>>>>>
>>>>> This list hosted by: http://www.qsl.net
>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>
>>>> ______________________________**______________________________**__
>>>> Milsurplus mailing list
>>>> Home: http://mailman.qth.net/**mailman/listinfo/milsurplus<http://mailman.qth.net/mailman/listinfo/milsurplus>
>>>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>>>> Post: mailto:Milsurplus at mailman.qth.**net <Milsurplus at mailman.qth.net>
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>
>>>>  ______________________________**______________________________**__
>>> Milsurplus mailing list
>>> Home: http://mailman.qth.net/**mailman/listinfo/milsurplus<http://mailman.qth.net/mailman/listinfo/milsurplus>
>>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>>> Post: mailto:Milsurplus at mailman.qth.**net <Milsurplus at mailman.qth.net>
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>>
> ______________________________**______________________________**__
> Milsurplus mailing list
> Home: http://mailman.qth.net/**mailman/listinfo/milsurplus<http://mailman.qth.net/mailman/listinfo/milsurplus>
> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
> Post: mailto:Milsurplus at mailman.qth.**net <Milsurplus at mailman.qth.net>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>