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Author Topic: Capacitors for Band Pass Filters  (Read 7598 times)
KM5PS
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Posts: 86


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« on: May 21, 2014, 06:30:43 AM »

I am trying to find 30pF 4000v disk capacitors for building Band Pass Filters.  I am going to build the W3NQN filter which is described in the Clean up your Signal in 1998 June QST.  I have found all of the capacitors except the 30pF 4000V ones.
I have looked at Digikey and Mouser and have not been able to find them or at least don't want to buy a 1000 of them.  I have also looked on ebay with no luck.  I have found some 30pf 3000v from overseas.  Anyone know of a good place to buy these capacitors, or if someone has some, I would like to buy some from them.  I am needing abt 15 of them.  Thanks for the
help.

John
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VK3AMA
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Posts: 9




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« Reply #1 on: May 21, 2014, 06:10:06 PM »

Is combining capacitors in series to increase the breakdown voltage not an option?

two 60pf 2000V caps in series is equivalent to 30pf 4000V

de Laurie, VK3AMA
« Last Edit: May 21, 2014, 06:16:07 PM by VK3AMA » Logged
LA9XNA
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Posts: 110




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« Reply #2 on: July 03, 2014, 01:47:50 PM »

Another benefit of using two capacitors in series is that two 5% tolerance capacitors give you 2,5%. So you get better accuracy.
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W6GX
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Posts: 3108




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« Reply #3 on: July 04, 2014, 07:43:04 PM »

I have the W3NQN BPFs built by Bob 5B4AGN.  He uses custom capacitors ordered and manufactured in small batches.  I don't know the technical details but there's probably a good reason for Bob to resort to using the expensive and custom capacitors.  His W3NQN filters are one of the best.

73,
Jonathan W6GX
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K5TED
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Posts: 809




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« Reply #4 on: July 06, 2014, 04:28:38 PM »

I have the W3NQN BPFs built by Bob 5B4AGN.  He uses custom capacitors ordered and manufactured in small batches.  I don't know the technical details but there's probably a good reason for Bob to resort to using the expensive and custom capacitors.  His W3NQN filters are one of the best.

73,
Jonathan W6GX

Well, there you have it. Unobtanium. You'll just have to buy the real filters and stop fantasizing that it's possible to actually build something on your own using alternative methods, instead pf buying in to boutique stuff so you can be in the club.
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KB2WIG
Member

Posts: 121




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« Reply #5 on: July 07, 2014, 09:47:37 AM »

Maybee this Co.


http://uk.alibaba.com/product/1644827984-VOLTRONICS-5GU300JEECANM-Ceramic-Disc-Capacitors.html

Surface mount?

http://uk.alibaba.com/product/1467045800-SMD-ceramic-capacitor-30pF-4000V.html

Build yer own?

http://www.westfloridacomponents.com/J613APK05/10pF+3000V+High+Voltage+Ceramic+Disc+Capacitor+Vishay+S100J25U2JR.html

Good luck,

klc
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