[TowerTalk] blown 10m section of ICE419 again

[David Robbins]

Very good, at least some people on here have been reading spec sheets.  while those cdv16 series capacitors cost more than some of the others that have the same capacitance and voltage rating they are much better for rf, especially transmitting, than most of the others.  compare this extract from their spec sheet:

CD16 & CDV16
"Ideal for snubber and RF applications, CDV16 mica capacitors now handle dV/
dts up to 275,000 V/μs and they assure controlled, resonance-free performance
through 1 GHz. CDV16/CD16 mica capacitors excel in both snubber applications
and high-frequency applications like RF and CATV. Type CDV16’s high pulse
current capability make them ideal for pulse and snubber applications. CDV16
capacitors withstand an unlimited number of pulses with a dV/dt of 275,000
V/μs. This is a 20% increase in dV/dt capability when compared to our CDV19
mica capacitors and CDV16’s are smaller too. CDV16 capacitors handle higher
peak currents — up to 825 amps. They also handle high continuous RMS current
at 5 MHz and up to 30 MHz. For example, a 470 pF CDV16 capacitor handles
6.2 A rms continuously at 13.56 MHz and it is 1/4 the cost of a comparable
porcelain ceramic capacitor. In addition to being great for snubbers, CDV16
is a fit for your RF applications. Their compact size and closer lead spacing
improves insertion loss performance — insertion loss data is flat within ±0.2 dB,
typically to beyond a gigahertz"

and compare it to something like the CD5, CD6, CD7, CDS5, CDS10, D7, CDS15, CDS19, CDS30 spec sheet:

Small cases for tight places is what you get with CDE
miniature dipped silver mical capacitors. Like the standard
dipped mica capacitor, the miniature dipped product
offers the same stability and rugged performance in low
and moderate-humidity applications.
♦ Reel packaging available
♦ Dimensions meet EIA RS153B specification
♦ 20,000 V/μs dV/dt pulse capability minimum
♦ Non-flammable units that meet IEC 695-2-2 are
available

Note that the second sheet doesn't talk about RF applications, continuous rf currents, etc... the first one has dv/dt rating of 275kv/us where the second one is only 20kv/us.  also the second one doesn't give data about frequency ranges.   

If you go to buy capacitors for RF applications be very careful and don't jump at the first one that has the right capacitance and voltage rating... you must remember to consider the current rating as well.  and for TX filters don't just assume that 200w in 50 ohm coax gives a max current of 2a... the circulating current in a resonant filter section can be much higher and can be made even worse if the line it feeds isn't matched properly.


Oct 2, 2013 07:51:49 PM, k6ll.dave at gmail.com wrote:

How about four of these:
http://www.mouser.com/ProductDetail/Cornell-Dubilier/CDV16FF131JO3/?qs=sGAEpiMZZMtLiKaZgV7flU44AUKbBD%2fXW8YQ%2f4vnaRY%3d


Dave Hachadorian, K6LL
Yuma, Arizona




-----Original Message----- 
From: WW3S
Sent: Wednesday, October 02, 2013 3:15 PM
To: towertalk at contesting.com
Subject: [TowerTalk] blown 10m section of ICE419 again

Both ICE 419 filters blew the 10m side again....both were already
repaired using the CDE 1000v series caps from Mouser, one had 2
270 pf in, and the other had 3 180 pf.....the one with 2 blew
almost right away, the one with 3 lasted a 2-3 hours
maybe....running just 100w into a Cushcraft A4 with what appears
to be low enough SWR.....before I order again from Mouser, any
ideas?

73, Jamie WW3S

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