[Elecraft] Electric fence QRM?

[Brendan Minish]

At 18:59 10/07/2003, you wrote:
>Any tips on eliminating or reducing Electric fence QRM, apart from moving !

Here is a copy of an article I did for our club magazine a few months ago 
on this very subject. I own an electric fence as do most of my neighbors. I 
have yet to discover a problem that could not be easily fixed, no need to 
move house !
  One other poster's suggestion of suppressing the charger is not really 
going to help unless it is a truly ancient fence charger.

E-mail me directly if you need some more help or have any other questions



Electric fence noise

That Horrible Click, Click Click noise that most of us who live outside 
towns have to put up with. The good news is that it's easy to fix.

Almost all of the impulse type nose from electric fences is due to poor 
joins between sections of the fence which causes sparking, An electric 
fence with poor joins is simply a spark gap transmitter connected to a very 
long antenna! However if the joins are repaired the noise will go away as 
you have removed the spark gap.

The usual method of making joints in electric fence string or tape is to 
tie a knot, this tends to make poor electrical connections (but usually not 
so bad that the fence actually stops working)
The simple way to improve on this method is to leave a couple of Cm excess 
on each end sticking out of the knot, you then burn (Use a Cigarette 
Lighter) a Cm or so of the String off each exposed end, wait till it cools 
and twist the exposed wires together. The Knot carries the strain and the 
exposed strands make a reasonable electrical connection and prevent 
sparking. I do this at every joint I make. If the fence is made out of 
Solid wire Re-do any suspect joints then apply some grease to prevent the 
joint rusting or oxidizing again.

I suggest you turn off the fence BEFORE making any repairs!
Once livestock are in a field with an electric fence for a day or two they 
get used to the idea that the fence is painful to touch and stop testing it 
so it is possible to turn off the fence for a couple of hours to make repairs.

Sometimes it is easy to find the bad joins in the fence as on occasion the 
sparks will be big enough for you to hear them by ear on a calm day, 
however it is well worth walking the entire length of the fence and 
repairing all the suspect joints and checking for poor insulators or weeds 
touching the electric fence.

If you cannot find the suspect join or insulator try using an AM Airband 
receiver as you walk along the length of the fence, the clicking will get 
much louder as go get close to the bad join.

Other things worth doing

At Gate handles apply some grease after first cleaning the connectors. The 
grease will prevent (for a while anyway) the connections oxidizing and 
going bad again.

I have had some problems with insulators getting leaky in areas that 
receive no sunlight due to an almost invisible build-up of green mould

  Make sure that the fence unit is properly grounded, the fencer's built in 
suppression relies on good grounding.

If the fencer is on low power put it on high power temporarily and you may 
be able to hear the bad join sparking as you get close.

If it's not your Fence then please try to co-operate with the owner of the 
fence, He probably doesn't think there is anything wrong with the fence 
(after all the animals are still in the field!) and is unlikely to want to 
spend any time fixing it, but if you don't fall out He will probably let 
you spend time fixing it, after all you are not going to break anything and 
when You are finished His fence will probably be working better than it was 
before you started.
If the owner of the fence lives close to the fence you may even improve His 
TV reception when finished as the fence can cause TVI if particularly bad!

Watch out for Bulls!