Electric fence interference
#1
Hi
I am pretty sure I have been getting interference from an electric fence. It was only abut 20M away from my antennas but has now been moved further away. I have set the gains right down but now hardly ever pick up lightning. Maybe better than swamping the servers with useless signals. 
So A) can anyone identify the trace below as really being the fence and B) would direct earthing of the H field shields help. Or any other tips for that matter.
Thanks
Alan


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Stations: 2004
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#2
Hi Alan,

I can't answer that, but my local electric fence pulses were helped by selecting Auto Adapt to Noise.

Manual mode; Auto Thresholds disabled.
Regards,
Mike W.
Stations: 1977, 2294
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#3
(2019-06-03, 19:32)Alanpenwith Wrote: Hi
I am pretty sure I have been getting interference from an electric fence. It was only abut 20M away from my antennas but has now been moved further away. I have set the gains right down but now hardly ever pick up lightning. Maybe better than swamping the servers with useless signals. 
So A) can anyone identify the trace below as really being the fence and B) would direct earthing of the H field shields help. Or any other tips for that matter.
Thanks
Alan

Alan, Cutty started a real good collection of various noise sources with screen shots and contains ways to mitigate some of the 'junk'

http://www.wxforum.net/index.php?topic=20439.0


Maybe you can match up your signal and go from there.

Best of luck.

Dries

PS. Maybe we can start a similar thread on this forum
[Image: NOAARADlogoTXT80.png][Image: forfaviconTXT.png]

Station: 2100
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#4
Seems like there are several types of the 'fence' installations...
From following for several years...
"Mechanical"
1.  One type can develope an open, or intermittent on a 'ground' return cable. Fauloty inksulators, corroded 'hot' lines.
     I recall the 'buried' RF type being susecpitalo to something similar... intermittent  radiator cable.  that tyoe of thing.
2.  Some have adjustable intensity, and can be 'dialed' down to still be effective, but 'emit' less.
3.  Foliage or other contact with fence.
3/ Some can be changed from 'pulse' to 'continuous'...

I seem to recall one situation using a 'solar' driven 'fence' with noise from the power supply... confused memory on what the fix was, but I thinki he mounted the panel on fiberglass/pvc rather than metal. earth support.  I think he may have tried a 'Faraday' at one point enclosing the modules.

One thing  to keep in mind... Generally, about all it takes is to get those 'noise' pulses below 'trigger' levels... and set your 'don't send' percentage a bit higher perhaps if you' got it set >10%... (I think default is ' 10%")  so if a channell triggers at 100 mv, other channels below 90 mv won't send the lower signal... and  trigger, perhaps, a false positive. or double strike perhaos... etc.

If it's electrical 'spark', not near field magnetic, experiment with some shielding approaches... for H field.. won't help with E field however.   The "Pesky Box" seems a bit more effective on very short 'sparks;'...
https://www.ourspecialnet.com/Weather/Pesky-Project/
and utilized with the "CSS Thingy" ferrite build, with it's slightly better efficiency, has helped greatly on some 'interferers' in my 'noisy' environment.. The CSS Thingy appears to help slightly with what appear to be Horizontally polarized 'near field' magnetic.
http://sferics.us/misc/CSS%20Thingie%201b.pdf  (50mb). There is a "V2" also, a few of us use... with the 'rod' sections first inserted in a thin' heat shring' for added stability, then the  'core shield'... Both variations are effective, but I don't think the V2 is quited as efficient in terms of response time... a bit closer to a 'normal' build than the owriegeinal V1 with it's 2-4 µsec response improvement.
All three of my stations now use CSS Thingy ferrite builds ...

Stations: 689, 791, 1439
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#5
Excellent, Cutty!

After reading this I turned off Auto Adapt to Noise (which helped eliminate evenly-spaced electric fence pulses), and raised the thresholds as you suggested.

I found that adjusting thresholds by only 5 mV has the same effect as changing the gains (the European servers have to readjust over some period (?) of time). Following your advice, I haven't changed my gains at all for some time now.

Please check your email.  Smile
Regards,
Mike W.
Stations: 1977, 2294
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#6
(2019-06-03, 19:32)Alanpenwith Wrote: So A) can anyone identify the trace below as really being the fence and B) would direct earthing of the H field shields help. Or any other tips for that matter.

I don't think either of the signals are an electric fence. The small regular and alternate polarity ones are at about 10 kHz, fences tend to pulse at 1 Hz or less. The signal in the middle doesn't have the amplitude that I'd expect from a fence only a few tens of metres away.
Cheers
Dave.

Stations: 1627
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#7
(2019-06-03, 19:32)Alanpenwith Wrote: Hi
I am pretty sure I have been getting interference from an electric fence. It was only abut 20M away from my antennas but has now been moved further away. I have set the gains right down but now hardly ever pick up lightning. Maybe better than swamping the servers with useless signals. 
So A) can anyone identify the trace below as really being the fence and B) would direct earthing of the H field shields help. Or any other tips for that matter.
Thanks
Alan

An electric fence should show as  a pulse lasting ~ 200uS every 1- 1.2 seconds.

Even with 4 fences in the neighbourhood (including mine), that leaves plenty of time between the pulses to detect lightning strikes.

I spent a lot of time trying to tame my fence with limited success. I went solar to get the controller away from the house but I have gone back to mains power for the winter.
The solar did help mainly due to lower power.
I tried all sorts of ferrite filters with negligible effect.
I replaced every insulator on the property.

The one thing I did find out was - my gate crossings go underground. It is the underground runs that cause most of my interference.
Unfortunately, I don't have the option of eliminating all of the underground sections.

   
My fence at one stage during the testing.
Stations: 2048
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#8
There is no ferrite mix that will work at ELF.
#26 powdered iron probably will. See my question and the answer at https://ham.stackexchange.com/questions/...0004#10004
Regards,
Mike W.
Stations: 1977, 2294
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#9
(2019-06-15, 05:46)tassyjim Wrote: The one thing I did find out was - my gate crossings go underground. It is the underground runs that cause most of my interference.
Unfortunately, I don't have the option of eliminating all of the underground sections.

That's interesting, why do the underground sections make the interference worse? Betrer coupling of pulse to the real ground? Blitzorgtung receiver floating with respect to the real ground so "sees" these pulses? Tried connecting the receiver chassis/0 V line to real ground? Possibly using a proper earth spike, rather than your electricity suppliers "earth".

Gate crossings:
It's only a fairly light weight wire, no chance of a couple of poles of suitable height each side of the gate to fly the cable over?

Or run an insulated bit of insulated fencer wire along the gate to a spring loaded handle and gate break post insulator or maybe some form of automatic "switch" that makes/breaks with the gate? Obviously not much use if the gate is normally open...
Cheers
Dave.

Stations: 1627
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#10
(2019-06-17, 10:23)allsorts Wrote:
(2019-06-15, 05:46)tassyjim Wrote: The one thing I did find out was - my gate crossings go underground. It is the underground runs that cause most of my interference.
Unfortunately, I don't have the option of eliminating all of the underground sections.

That's interesting, why do the underground sections make the interference worse? Betrer coupling of pulse to the real ground? Blitzorgtung receiver floating with respect to the real ground so "sees" these pulses? Tried connecting the receiver chassis/0 V line to real ground? Possibly using a proper earth spike, rather than your electricity suppliers "earth".

Gate crossings:
It's only a fairly light weight wire, no chance of a couple of poles of suitable height each side of the gate to fly the cable over?

Or run an insulated bit of insulated fencer wire along the gate to a spring loaded handle and gate break post insulator or maybe some form of automatic "switch" that makes/breaks with the gate? Obviously not much use if the gate is normally open...

I have tried all variations of earthing, both for the fence controllers and the receiver.
Going overhead is not an option I like.
I might try using some RG213 co-ax for the underground sections in the hope that the shielding has some effect. It makes for an expensive fence though.

I assume the signals are getting coupled to the ground and traveling to the shed.
My receiver is inside a steel shed.

I will do some more experimenting when the weather warms up a bit and the sun is string enough for me to go back on solar for the fence,
Stations: 2048
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#11
An improvement (reduction) in the level of interference generated can be made by making the connection from the fence power output to the fence wiring a low resistance path.  I found the noisy connection had been made with an oxidized aluminum wire and could hear the connection popping on each electrical pulse. I replace the aluminum with a tin plated copper wire (something like 14 or 12 gauge solid) and used a wire nut to connect the tinned copper to the galvanized fence wire. This made a noticeable difference  in the amount of signal seen by system blue H channels.  I did not retest with the oxidized connection to verify the noise improvement.
Stations: 1888
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