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RFI choke

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NutmegCT

NutmegCT

Great Pumpkin
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My radio gets RF interference through its power cord. Whenever a light on the same circuit is turned on or off, a motor starts or stops, etc., the radio speaker makes a loud pop.

Is a ferrite ring choke the solution?

rct2.jpg


Wondered if a choke like this would prevent/reduce power line RF interference to the radio if placed around the radio's 110v power cord?
Thanks.
Tom M.
 
No, probably not enough filtering. I'd start by putting a large capacitor in parallel with the power line to the radio. I'd use something on the order of 1000 microfarads, with a voltage rating of 20 volts or more. The capacitance value is not critical; 500 or 2000 would be OK too. Just don't expect a 1 microfarad cap to do much. A higher voltage is OK but not a lower one. Capacitors of that value are polarized, so be sure it is connected with the + terminal to + voltage. Some are not marked + or -, but instead have a circle around the - end.

Mount it as close to the radio as reasonably possible.

If this doesn't work, there are more complicated filters possible, but usually this is enough. I had a similar problem in my Porsche, and it solved it. You'd think that radios designed for automotive use would have better filtering, but they almost never do.
 
Thank you Steve!

I have a 1000 mfd capacitor, but don't know how to mount it. Could you tell me exactly how I put it "in parallel" with the power line?

Obviously, the line has two wires running from wall outlet to radio, so I can't visualize how the cap would be hooked up.

Thanks.
Tom M.
 
Is that + to the live terminal and - to the neutral?

My radio does the same thing when some lights are turned on. I have found that by rotating the radio I can reduce or eliminate the noise.

David
 
Hold on....Are we talking about car radio or home radio??? DO NOT connect a capacitor to a AC line!!!! sarastro assumed you were talking about a car radio!!
 
George_H said:
Hold on....Are we talking about car radio or home radio??? DO NOT connect a capacitor to a AC line!!!! sarastro assumed you were talking about a car radio!!
Click to expand...

AMEN!!
 
Yep - a 120v AC powered radio. (That's why I've been confoozled about the "put a capacitor in parallel with power line".)

What can I use to reduce/eliminate pops when other electrical devices are turned on/off?

Thanks.
Tom M.
 
I would try an RFI choke to start with. It may also be a problem with the radio. What type of radio are we talking about? Antique tube type? AM? FM? modern?
 
Thanks George. It's my 1930 Atwater-Kent Model 74. AM only. Definitely "tube type".

When you say RFI choke, I assume you mean clasped around the 120v power cord?

And what size (mfd) choke?

thanks.
Tom M.
 
George - you are a goldmine! I'll contact Palomar tomorrow.

Yes, a 30' antenna wire, and a separate ground wire to house electrical ground. AK recommends either a 30' indoor wire, or a 100' outdoor aerial.

At night I get around 20 stations; daytime around 10.
 
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