Topband: AC line bypass capacitors

[Charlie Cunningham]

Hi, Harold - well it's been a while, I know that we regularly used line
bypasses in electricity meter and they had to be really robust, but I was
mostly and RF and communications guy and when I had to fool with power
supply designs for the meters, I generally just copied whatever was done
before. Of course out there on the line side of the meter is a hellish surge
environment. On guy mentioned film capacitors, but I would be a bit
skeptical of those as RF bypasses. The capacitors that we used were very
robust, as they had to withstand 480 volt high-line voltage or 530 VAC. And
yes I have seen my share of fried line bypass capacitors  in consumer
electronics and radio gear.

73,
Charlie, K4OTV



-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of HAROLD
SMITH JR
Sent: Wednesday, February 04, 2015 9:16 PM
To: Charlie Cunningham; 'Paul Christensen'; topband at contesting.com
Subject: Re: Topband: AC line bypass capacitors

Hi Charlie,

I can remember when the Collins S-Line used .01 600volt disk ceramic
capacitors on the power supply connector. They were from the AC switch to
ground. They were almost always burnt and many times only the leads left. 

73 Price W0RI


On Wednesday, February 4, 2015 6:31 PM, Charlie Cunningham
<charlie-cunningham at nc.rr.com> wrote:
 


Hi, Paul

For AC line bypass capacitors look for UL-rated Ceramic Disc capacitors that
typically have AC working voltages like 250 VAC or higher. These are
designed and rated for AC line service and can take the surges that occur on
AC lines.

Check Digi-Key, Newark and others - you'll find plenty!

73,
Charlie, K4OTV



-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Paul
Christensen
Sent: Wednesday, February 04, 2015 3:55 PM
To: topband at contesting.com
Subject: Re: Topband: AC line bypass capacitors

>
>My 160 TX is causing RFI to one of my baseboard heater programmable 
>thermostats (switches modes, temperature, when I transmit). The 
>thermostat  has a 2 wire connection to 240VAC in a metal receptacle box 
>that has a  third wire common ground wire. I would like to try 
>bypassing the AC line.
> Can someone suggest an appropriate (safe) capacitor for this purpose, 
>e.g.
> a Digi-Key or Mouser part number? Should I use one capacitor across 
>the  240VAC or two capacitors, one from each 120VAC line to the common
wire?
> Thanks for the help.
> _________________

As a substitute for X1 Y2 line caps,  an in-line RFI/EMI filter can be
used that already contains the X/Y-rated caps.   See the bottom of p. 21:

http://audiosystemsgroup.com/RFI-Ham.pdf

These filters can often be cannibalized from old PC power supplies and
discarded industrial equipment.

Paul, W9AC


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