AM Interference from power lines

**101RRS** · 28th February 2010, 01:30 PM

As`anyone who lives in Canberra will know - the electricity authorities in their wisdom run the power lines along the back fence between houses. I guess it is so they don't have to pay to keep trees 1.5m away from the wires as they would have to if the cables were on the nature strip. At my place, as well as wires down the back I also have them at the side of my house probably less than 20 feet from my living room.

As we know AM radio reception and power lines generally do not mix. My little portable radio that I take camping does a reasonable job of filtering out the static (it is still there) but my main radio (the TV surround sound Rx) cannot manage it. The static from the wires is so strong that it all but drowns out the AM stations. I have adjusted the provided loop antenna so that AM strength is strongest but you still cannot listen to AM.

So for the radio buffs out there - is there anyway I can improve reception given the proximity of the wires - the surround sound Rx needs to stay in its current location - though moving further away does not seem to help matters much.

Thanks

Garry

**JDNSW** · 28th February 2010, 02:23 PM

You probably need to supply a better antenna to your receiver - unfortunately, these days they often have pretty poor performance on AM ("who listens to AM?"). The antenna on the receiver is probably also surrounded by power leads, and it is likely that these are providing at least some of the noise (a noise filter on the power to your system may help). A larger, loop type antenna, coupled to the one supplied is likely to improve the reception, particularly if it can be located somewhere further from the power lines (including the wiring in the house). I seem to remember something along these lines being described in the magazine Silicon Chip in the last year or so.

While the noise is probably largely generated by leakage on the insulators of the power lines, it is also brought into your house along the power lines, and this is likely to be the problem rather than the location of the power lines relative to the house.

John

**Sleepy** · 28th February 2010, 02:24 PM

Garry,
Often, interference can come via the electricity supply as well as radiated.
A cheap first step would be to fit Ferrite beads to your power in.
[ame=http://en.wikipedia.org/wiki/Ferrite_bead]Ferrite bead - Wikipedia, the free encyclopedia[/ame].

Next I would check your earth. Not sure what radio you are talking about but if there is an RF earth I would use that too. ie: run a separate earth just from the radio to a earth stake in the garden

Next step is filters - there are many types available for ham radio equipment and you could adapt to your also - although this will cost more $$$ than above.

Here is some light reading too.

ACMA - CB radio & interference
FCC Interference Handbook - Courtesy of Radioing.com

**101RRS** · 28th February 2010, 02:53 PM

Thanks John and Paul.

While possible, it is unlikely the interference in this case is coming through the power lines to the house. It also upsets my car radio and as soon as I am out of the driveway and on my way the static goes.

I will investigate a better aerial and earthing the unit somehow and I will see how I go - my portable has a ferite rod inside and does work much better.

Cheers

Garry

**Narangga** · 28th February 2010, 02:53 PM

All of the above, and when you have finished reading then you may be interested in one of these too

PK's Loop Antennas

**Mick_Marsh** · 28th February 2010, 09:22 PM

I would suggest its caused by tracking across insulators on the power lines. It's getting to the end of summer, there is a dew in the mornings. I think it may be caused by electricity tracking across the damp dust that has collected on the insulators over summer.
Power suppliers used to wash these insulators over summer if they became a problem. They usually were cleaned by rain.
I'm not sure what the weather has been like in Canberra but, here in western Victoria the rain has been either heavy and short or non-existent. Probably not good enough to clean the insulators.
Find out if the supply authority still cleans the insulators.

regards
Mick

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