[CQ-Contest] Bandpass filter
kdutson at sbcglobal.net
Wed Jul 11 08:42:49 PDT 2012
Thanks for the SPICE model.
73, Keith NM5G
From: cq-contest-bounces at contesting.com
[mailto:cq-contest-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Monday, July 09, 2012 7:10 AM
To: Keith Dutson; cq-contest at contesting.com
Subject: Re: [CQ-Contest] Bandpass filter
> I can relate to the problem of capacitors with lower than sufficient
> voltage rating. I use the ICE 419 banpass filters while on
> DXpeditions. I have two A models and two B models. Both models do a
> good job rejecting out-of-band crosstalk. However, the caps in the 20
> meter and up tuned circuits have heated up, resulting in high VSWR.
> This usually happenes when the operator switches the transmitter to a
> different band but does not remember to change the filter until AFTER
> transmitting and seeing high VSWR. Ten meters is by far the most
> vulnerable section. I have a large supply of 270pf 500v silver mica
> caps on hand to make repairs. Two of these caps are wired in parallel
> to get 540pf for the tank circuit. If I could find caps rated at
> 1000v, I would use them.
I added a SPICE model of two low pass 3.6 MHz filters to my webpage. You'll
see the stress on parts there for a 100 volt peak source through a 50 ohm
resistor, which is about like a 50 watt transmitter when matched.
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