[TowerTalk] Fwd: Polarity question..on a dipole

HansLG at aol.com HansLG at aol.com
Sat Apr 1 18:01:45 EDT 2017

I don't think the RF power from an electric fence is enough to even get a  
measurable temperature increase on those insulators. The voltage is high but 
the  duration is short. 
I just wonder if you put an LP filter on the output on the pulse generator  
that would help the annoying pulse interference. Yes, the LP filter has to 
be  designed for the high voltage, that is, the capacitors has to be of a 
high  voltage type. If you can increase the rise and fall time of the pulse 
you would  get less RF to leave the wires. Just an idea.
73 de,
Hans - N2JFS
In a message dated 4/1/2017 9:22:52 A.M. Eastern Daylight Time,  
patrick_g at windstream.net writes:

All the  fence chargers I have seen have a pulsed output.  I have not 
examined  the waveform of their pulses with an o'scope but suspect the 
pulses  contain significant RF since I can clearly hear them on my Flex 
5000A on  multiple bands.  A minor annoyance listening to an approximate 
1/sec  noise burst but not enough to motivate me to walk out to the barn 
to shut  it down then back again to turn it back on, especially if it is 
cold  out.

Luckily my antennas are not close to any of the electric fence  spans.

Just guessing but if the RF component of the pulses were to be  
penetrating the plastic insulating tubing, i.e. shorting out to grounded  
metal in contact with the tubes OD or if the RF were getting through the  
tubing to the damp earth where it is buried I would have thought that  
would have selectively attenuated the RF before it was propagated down  
the fence wire and radiated where my antennas could pick it up.

The  fence charger itself is inside a well grounded all metal building.   
If the charger is running but not connected to the output wire the radio  
does not detect pulses so any noise emitted by the charger itself is  
contained within the building and additionally does not get to the shack  
via the AC wiring as no pulses are heard if the output is not connected  
to the distribution system/fence wires.

The tubing is cheap so I  would give it a try before writing it off if I 
needed to insulate a wire  antenna from something.

Patrick         NJ5G

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