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eHam Forums => SWL (Shortwave Listening) => Topic started by: K4NYA on November 29, 2011, 07:57:38 AM



Title: Dealing with RFI on a portable SW
Post by: K4NYA on November 29, 2011, 07:57:38 AM
I've got the Buzz Aldrin addition of the Grundig G6.  Until I get my Dad's old National tube radio going again, this is my only radio for SWL.  However, I'm getting a lot of RFI from someplace.  It's always been really bad from 2000mhz to 5000mhz, but has lately become a problem on 31 meters as well.  Not sure where it's coming from, unfortunately.  What would be a good way to minimize this interference?


Title: RE: Dealing with RFI on a portable SW
Post by: AD4U on November 29, 2011, 09:13:19 AM
I assume you meant you hear the noise from 2 - 5MHz and not from 2000MHz to 5000MHz where noise generally is not an issue.  2-5MHz is generally "noisy" when compared with the higher HF frequencies.  Atmospheric noise and lightning crashes can often be heard hundreds of miles from the source.  There is not much you can to to eliminate this noise.

It is MUCH better to eliminate the noise than to try to mask it.  My guess is something inside your house is causing the noise.  Typical noise sources are TV's (even when turned OFF), computers, computer monitors, alarm systems, touch activated lamps, etc.  

If this is a battery operated radio, "kill" all power to your house by flipping the main circuit breaker in the breaker box to OFF.  Does the noise go away or nearly so?  If it does something inside your house is causing the problem.  Unplug various electrical devices one at a time until the noise is reduced.  Continue until you identify the culprit(s).

If killing all power to your house does not identify the problem then obviously something outside of your house is causing the noise.  Typical culprtis are power lines arcing, electric fences, and / or devices in neighboring houses.

If you do not have an outside antenna, by all means install one.  This often helps.  One thing to remember, grounding the radio WILL NOT reduce the noise.

Dick  AD4U


Title: RE: Dealing with RFI on a portable SW
Post by: K4NYA on November 29, 2011, 11:08:53 AM
Yes, you're right.  Got my megahertz & kilohertz confused again.   ;)

An outdoor antenna would be idea, but it would overload this little guy's front end something fierce!  Something to think about when I get the old National up & running.


Title: RE: Dealing with RFI on a portable SW
Post by: K4NYA on December 01, 2011, 08:27:02 AM
You were certainly right about RFI come the TV!!!

I shut if off at the power switch last night & almost all my interference ceased.  Still getting a bit of 31m, but not nearly as bad.  Thanks for the tip!


Title: RE: Dealing with RFI on a portable SW
Post by: WA4053SWL on December 01, 2011, 09:14:05 PM
The plasma or LED TV is terrible interference does in 31 meter, 10.000 to 8.500 Khz approx. find strong interference with portable receivers and batteries, put an indoor loop antenna like DE31 that move to override the noise does some good work.
Try to filter the source of interference, put ferrites to cable TV or something.