Electric Fences And Digital Reception

[wahroonga farm]

Ah! The trials of DTV-T reception on marginal links in the bush.

My guess is that this is an area not often tested to date as DVB-T roll-out and uptake is not all that great in the sticks.

We all know that impulse noise is well tolerated by our wonderful analogue Pal TV with it's AM video and FM sound.

Sure ..... you can see impulse noise on analogue, but it's virtually un-noticeable ... a line or two blanked by the noise and that's it. Sound is unaffected.

So roll on electrical storms, gas stove igniters (common in the bush) and high powered electric fences. Analogue rocks!!!

But Digital is another kettle of fish.

I helped with a neighbourly DVB-T install the other day some 90Km out (on an obstructed path) from a high powered regional transmitter (Middle Brother, NSW).

Did the antenna dance with primitive equipment (STB that resolves C/N .... sort of and a tele). Got reception at 18db C/N ... but lots of pixellating. Oh well find a better spot. 21 dB still pixellating. and finally 24.1 (the poor old stb mysteriously max's out at 24.1), but .... bugger no noticeable improvement in the BER.

At this level analogue was perfect. Almost totally noise free, ghost free .... 110% watchable at 'SD resolution'.

So what was the problem?

Close inspection of the analogue video, showed the tell tale blips of impulse noise. Just a line or two ...... not really noticeable (the brain and persistance is a wonderful thing).

But Digital was crap awful. Audio was holding 98%, but video continuously pixellated badly.

Analogue gave it away again. The noise blips were regular .... electric fence regular!

So turned off the fence, and error free DVB-T streamed in. Beautiful SD digital in all it's glory ABC2, SBS 2, Dig radio ....... ah, country bliss.

The bulls promptly all escaped, ran amock and raped the neighbours cows ..... kidding actually , but that was on the cards, ........ so the fence went back on.

Turned on the am radio and two seperate fences were plainly evident. So I left with the advice that the problem was most likely due to a fault in the electic fence ... an arcing fault, ..... in reasonable proximity (200m?) to the antennas location. But hell, I don't really know??

So back to my place where my severely obstructed paths DVB-T reception had slid downhill recently.

Bit of damp weather and morning dew seemed to be instigators. Now I can only just detect my electic fence on the am radio, but I switched it off ... and presto error free DVB-T again. I'm sure this fence has a fault (not yet diagnosed), but no bulls so the bloody thing's off

Tried a smaller fence a couple of km away which is fault free. Had to park on top of the fence to 'hear' it. 50m away and nothing.

Soooooo!

Electric fences are absolute dynamite to DVB-T. Pretty obvious of course, but there it is.

Roll on the analogure turn down

So my question, after this long tale, is; are there techniques to 'quieten' a high power electric fence, without reducing it's punch (joules)!

Or must they be maintained in 100% tip top order, no wet grass touching, no frayed tapes, no rusty joints etc etc?

And as far away as possible (which since the 'farm house' generally has power and is the point where fences radiate from ... nigh on impossible.

Interesting there aren't other 'impulse noise sources' dealt with in this section of the forum???

[I am not a duck]

Ah! The trials of DTV-T reception on marginal links in the bush.

My guess is that this is an area not often tested to date as DVB-T roll-out and uptake is not all that great in the sticks.

Probably because those of us who do this on a regular basis have developed their own ways of providing reception in marginal areas where customers do not want or have the means to go down the alternative path.

eg I have installed with no overhead and down to a Pv BER of 2E-5 utilising reflected signals after explaining to the customer the difficulties likely to be encountered in doing this.

Impulse noise is a clear and present danger in this situation and using an instrument capable of displaying non recoverable errors is vital in determining antenna type and positioning.

Determining sources of impulse noise in these situations can also be an intersting adjunct to a day's work.

Sometimes it would be nice to have signals in the millivolt range, but then where would the challenge of an unrequited life be?

[alanh]

Wahroonga farm,

I suggest you do a search for electric fences. Its all been covered in depth before. Impulse noise in covered in the antenna strand.

AlanH

[wahroonga farm]

Hi Guys,

It's the optimal noise mitigation of an electric fence that I'm raising.

I suspect a 100% fault free fence with 'perfect' earth return grounding, star configuration and low fence impedance, is the optimal solution. No doubt more technically demanding than antenna installation. Tricky measuring impedance with 6Kv.

Oh and modified rise time energisers may be helpful. Any experience?

I'm not trying to 'take it out', by all the various tricks of the trade. Consider that done. However it's like fixing the fence after the horse has bolted

PS Impulse noise interference 'removal' is discussed elsewhere .... well sort of.

If the noise field is stronger than the signal field ..... so much better to treat the source

Island Antenna's post here is typically helpful Note: Find your way round the Telstra link to 'Tips' and then 'Line interference'

[GHE]

It would be good if every area kept an analog channel with a test patern available so we could see the impulse noise. It's much easier to diagnose that way. How are we gonna do it when it's all digital?

[I am not a duck]

How are we gonna do it when it's all digital?

I find the use of a small portable am radio and a digital field strength meter capable of indicating RS uncorrected errors quite useful.

Fixing the offending fence is not always easy if it isn't on a customer's property.

Having all digital transmissions on UHF (such as my service area) is also helpful in reducing the effect electric fences cause.

[HillsTas]

I had a similar event recently but with a dog fence (a perimeter wire buried underground which triggers a collar worn by the do to give it a volt jolt). After not finding an electric fence, and half an hour of searching for the source of the IN, he finally noticed the dog had a very large collar and asked the owner if they had a dog fence. Yes they do! The customer refused to admit the installer was correct in his theory of it causing impulse noise and even after he turned the system on and off many times, with the result of brilliant digital when off and major pixellation when on, the insisted he had no idea what he was doing and refused to pay him. The situation was eventually resolved with a large piece of rope!!!!...to restrain the dog of course.

So if there is no electric fence evident, keep your eye out for a dog with a large collar.

[Guest vtv]

Electric fences are a terrible problem in my area(Kilmore/Broadford area Victoria)

There are a lot of farms and horse studs in the area and almost every electric fence causes issues(apart from new fences when installed correctly).

The problem is they will all eventually cause a problem because grass touches ,them insulatorts age and livestock push them over.

In an ideal world the property owner would maintain them within the nth degree but this is rarely the case (who has the time?).

According to an AMCA inspector they can potentially interfere up to 5 kms from the source,try finding that on a job with the problem!

My solution has been where possible to use one of the regional UHF transmitters(Bendigo or Broadford or Seymour) and not using VHF from Melbourne or Shepparton.

And before anyone suggests using a VHF 6 and up digital antenna I already do and it usually doesn't get rid of the electric fence interference.

I have tried low band filters,braid breakers,6-12 VHF antennas all without much success.

I think some sort of regulation needs to be implemented to control the sale and installation of electric fence systems/units.

There are some fringe areas where VHF is required for digital signals,then the problems begin.

Of course you can ask the neighbour to turn off the fence but not everyone is as pleaseant as they could or should be.

I also have experienced the 'DOG' fence sitiuation mentioned,it was an actual electric fence attached to wooden stakes in the ground(the owner didnt want the dogs too get too much of a zap he said).

It was causing digital havoc and the dog owner couldnt understand why!

My way of finding the fence has been to drive around in the car with the am radio on and just off channel you can usually clearly hear the thump thump of the fence(or 2 thumps if there is more than one fence)

Anyway if anyone has solutions that will work long term let me know.

[alanh]

VTV,

AS/NZS 3014:2003

Electrical installations - Electric fences It is worth the cost. Use the instructions for minimising interference to telephone lines.

The reason why the interference is so bad is the arcing and the current resultant current flow. Earthing is very important. The arcing signal is picked up in the antenna cabling. The other thing required is to get the highest signal level on the cable without overloading the masthead amplifier. An attenuator at the receiver end can be used it is too much for the receiver. The attenuator will also reduce the interference.

The masthead amplifier must contain a bandpass filter for UHF or use a Kingray masthead filter prior to the amplifier if Band 3 is used.

AlanH

[charlesc]

The arcing signal is picked up in the antenna cabling.

I think you'll find the antenna is the main culprit for interference pickup, especially from external sources like electric fences.

If it was just coming into the antenna cabling, a good solution could be achieved by making sure high quality RG6 quad shield was used throughout, along with shielded components.

As you know, it's not that simple.

Perhaps you didn't exactly mean what was typed above?

[DrP]

Oh I dunno. Many a times I've been driving out west and come across mile after mile of antenna coax wrapped around the hot wire of an electric fence.

[Guest vtv]

VTV,

AS/NZS 3014:2003

Electrical installations - Electric fences It is worth the cost. Use the instructions for minimising interference to telephone lines.

The reason why the interference is so bad is the arcing and the current resultant current flow. Earthing is very important. The arcing signal is picked up in the antenna cabling. The other thing required is to get the highest signal level on the cable without overloading the masthead amplifier. An attenuator at the receiver end can be used it is too much for the receiver. The attenuator will also reduce the interference.

The masthead amplifier must contain a bandpass filter for UHF or use a Kingray masthead filter prior to the amplifier if Band 3 is used.

AlanH

The antenna picks it up typically Alan

I had another one today as a matter of fact, I placed the promax PRODIG meter on the Antenna and had pixellation despite sufficient BER and MER.

I believe the pulse of the fence(when its playing up) travels along the the fence wire and emanates out of it as a Electromagentic Rf pulse if you like(basically a long wire transmitter).

Once it is received then amplified the problem gets much worse.

Rarely has it been because of the cabling in my experience(although it would help to have good cable).

You have to remember in a lot of cases the Electric fence is a Paddock or more away and the Energiser unit is often in a shed a fair distance away it is anlikely to be because of the cable at that distance.

Getting a high signal and overloading the amplifier is almost impossible in my area as the passive signals are generally low

An attenuator is not required if the signal levels are balanced and the gain adjusted at the amp.

Anyhow after 20 years of experience I have tried most things (earthing etc as you suggested) and only when digital started did it become a huge problem.

As I posted before UHF is much easier to utilise when avaliable,then I can band stop everything below UHF.

I should also mention I have had Electric Fence interference on UHF at times and 1 job in particular was never done because the customer wasnt prepared to turn his fence off or fix it(his problem)

Finally the customers are the ones that need to take responsibilty for the Fences and maintain them properly I can only advise them as to why it is playing up, a well installed and maintained fence doesn't cause issues.

In summary,often(most of the time) no amount of fiddling with the antenna system can fix it ,THE FENCE MUST BE FIXED

[beeblebrox]

Yes It's usually the fence that needs to be fixed... there's the dilema quite a number of people who have electric fences are totally ignorant as to how they operate and very often haven't set them up properly or maintained them. I've had a few UHF problems too with fences both TV and radio mostly vhf though. and I'd agree with your observations in regards to cabling etc.

It's hard enough getting the ACMA out for arcing HV power lines let alone an electric fence in the middle of whoop whoop..

Was the PV BER on the promax not bouncing on the pulse.. usually that's what I've seen on my unaohm and my Ikusi meters. IT usually shows in the post viterbi signal and then the reed solomon counter (on the unaohm)

BTW there are dog collar systems that work on frequencies that won't have any affect, I know we have one and I made sure I check it's frequency and looked at harmonics before we forked out the grand for it and it works perfectly and has no affect on a dtv signal at all.

[alanh]

VTV,

I agree with you to fix the source. You will find the Australian Standard very useful. You can tell the customer what they have to fix.

AlanH

[Guest vtv]

Yes It's usually the fence that needs to be fixed... there's the dilema quite a number of people who have electric fences are totally ignorant as to how they operate and very often haven't set them up properly or maintained them. I've had a few UHF problems too with fences both TV and radio mostly vhf though. and I'd agree with your observations in regards to cabling etc.

It's hard enough getting the ACMA out for arcing HV power lines let alone an electric fence in the middle of whoop whoop..

Was the PV BER on the promax not bouncing on the pulse.. usually that's what I've seen on my unaohm and my Ikusi meters. IT usually shows in the post viterbi signal and then the reed solomon counter (on the unaohm)

BTW there are dog collar systems that work on frequencies that won't have any affect, I know we have one and I made sure I check it's frequency and looked at harmonics before we forked out the grand for it and it works perfectly and has no affect on a dtv signal at all.

Yes funnily enough the promax occasionally shows pre viterbi errors with the electric fence(the bounce you described is spot on),I assume its to do with the sampling rate missing the fence pulse?The good thing though is it has both an analogue and DVB tv display so I can readily see the problem on the screen

Ive made it a must to have a look at the pictures on the meter and not rely solely on figures,sometimes,only sometimes figures lie.

I am aware of the Dog collar systems(its a loop that interacts with the collar)I have never seen interference from these.

[Guest vtv]

I appreciate all the help and comments,it would be helpful(to me)if we can keep the information flowing.

I have been thinking that someone somewhere should invent an active filter for fast rise peak removal but I dont know whether its even possible at this stage.

[dig2all]

surely electric fences and digital tv naturally oppose each other. are the older fence electrics worse? new ones have to meet emisson standards which should make them better than they used to be. playing with the rise and fall time of the pulses might help but 6kv, ouch! can you see it on a cro? is there a low power setting that can be enabled when the tv is switched on?

[Guest vtv]

surely electric fences and digital tv naturally oppose each other. are the older fence electrics worse? new ones have to meet emisson standards which should make them better than they used to be. playing with the rise and fall time of the pulses might help but 6kv, ouch! can you see it on a cro? is there a low power setting that can be enabled when the tv is switched on?

Poorly installed and maintained fences old or new are a problem.

I would imagine older units would present more issues though.

A low power setting probably wouldnt work,the voltage is chosen to enable the voltage to pass through the object(animal) to ground with a suitable(but not dangerous) jolt.

The current is controlled to make it safe.

I dont believe the energizer units are the main issue anyway,its the wiring itself in the paddocks that is usually to blame.

Poor joins,bad or no insulators,corrosion,mould,grass touching,fence pushed over are just some of the issues and dont get me started on the Tape style wire(which should be banned in my opinion)

[alanh]

VTV,

An active filter which by definition has to contain transistors within ICs can overload just like the transistors in the masthead amplifier. As you say it is better to fix the source.

The standard I referred to shows how to set out the fence to minimise the radiation near the homestead. I also gives the minimum earth resistance required where the fence pulse unit is connected to the power supply.

AlanH

[Guest vtv]

VTV,

An active filter which by definition has to contain transistors within ICs can overload just like the transistors in the masthead amplifier. As you say it is better to fix the source.

The standard I referred to shows how to set out the fence to minimise the radiation near the homestead. I also gives the minimum earth resistance required where the fence pulse unit is connected to the power supply.

AlanH

I take your point alan but it is often someone elses fence and getting them to do anything that will cost them money(ie rewiring rerouting the fence) can sometimes be an issue.

It would be nice if a filter was feasable but I ,as you said ,also think by its nature it would have the same probelms as any other electronic circuit.

It would have to involve several inductive coils to control the spike to begin with and therein lies another problem because the spike will shift in amplitude and the frequency spread can vary as well(which would depend on where along the Fence wire the problem is and how bad it is I would imagine)

It is a predicament I encounter probably 2 times a week on average and I will pass on all the information and ideas to customers as needed.

God help us(me) when analogue shuts down.

[beeblebrox]

I take your point alan but it is often someone elses fence and getting them to do anything that will cost them money(ie rewiring rerouting the fence) can sometimes be an issue.

It would be nice if a filter was feasable but I ,as you said ,also think by its nature it would have the same probelms as any other electronic circuit.

It would have to involve several inductive coils to control the spike to begin with and therein lies another problem because the spike will shift in amplitude and the frequency spread can vary as well(which would depend on where along the Fence wire the problem is and how bad it is I would imagine)

It is a predicament I encounter probably 2 times a week on average and I will pass on all the information and ideas to customers as needed.

God help us(me) when analogue shuts down.

This is where the satellite VAST service could be used but the politics are likely to prevent it..

[Guest vtv]

This is where the satellite VAST service could be used but the politics are likely to prevent it..

Yes would constant and unrelenting interference qualify a customer for VAST?

Somehow I doubt it.

Ill tell you another BIG problem I have come across recently is local pubs trying to get decent VHF digital,every time a fridge or pump switches on and off they get regular pixellation.Now most pubs have say 10 to 15 or more fridges and lets say 3 or 4 have noisy thermostats so you can see the problem.

This is picked up by the cabling but recabling in these old buildings and keeping the cables away from every fridge and pump etc is nearly impossible and potentially very expensive.

I have already suggested to 2 Local hotels that they try methodically turning things off to find the culprits and then maybe get the thermostats or pressure switches etc replaced.

Also fitting suppressors across the thermostats would help(more expense)

Most country Pubs struggle to keep afloat already

Vast would be a great solution in these situations(if it is allowed)

[Guest vtv]

Had yet another 2 electric fence issues today.

1 was so bad the UHF was affected,the other I had to change the customer over to UHF regional instead of VHF Melb to get stable signals

One of customers own fence was to blame the other that I changed to UHF was someone elses fence(we are not sure where at this point)

GODDAMM Electric fences

[bellotv]

Had yet another 2 electric fence issues today.

1 was so bad the UHF was affected,the other I had to change the customer over to UHF regional instead of VHF Melb to get stable signals

One of customers own fence was to blame the other that I changed to UHF was someone elses fence(we are not sure where at this point)

GODDAMM Electric fences

vtv ,your not alone with this electric fence issue.

Although all my area uses UHF ,I still have issues with fences so I pity those like yourself that are trying to get VHF digital in an electric fence region.

I have no magic answer as I suspect there is none ( except banning them but that will never happen or work) ,however the only thing I have found to help is obviously getting the best signal to fence interference position when mounting the antenna.

I use an Unaohm T40a meter and as has been said by M'Bozo , I find the RU count will show bursts when the fence is interfering ,also on the spectrum analyzer,although its not the "real time" high resolution I would expect if I had an AP01 etc, I can still see the interference spikes in between channels and use this is an indicator relative to a desired multiplex to gauge where minimal interference will occur.

Education of the owners of fences can help.Most have now Idea. I have found it helpful as an incentive to get them to "Maintain" them by suggesting that if it is sparking out somewhere that there will not be a useful voltage on the fence to withhold their stock.This generally makes sense to most and also helps justify the whole existence of the fence.(If it ain't work'n ,whats the point of it be'in there) .

Others seem to go by the theory that the stock see the fence and just know not to go near it and simply turn it off when they want to watch something on telly,(bugger the neighbors)

One of MY neighbors strings up miles of white tape and doesn't even have a fence controller connected to it ( unfortunately one of his young calves wasn't quite so knowledgeable and me and my son had to round it up and put it back in the paddock) @#$%

If I have installed a digital antenna system on a rural property and get a call perhaps weeks ,months ,years later that there is Picture brake up ( pixallating) all of a sudden,first question is "do you have an electric fence" ? " Can you turn it off and call me back and let me know if it has or hasn't made a difference."If yes then I leave it up to them to find out where its arcing out.If not then its a service call.

Re : the pub issue

Miles of that shitty brown single shielded air spaced cartwheel crap tacked up right next to the power cabling with splitter after splitter .Every sparky and his dog have added a bit here and there and the owner wants it fixed for a few slabs.

Problem with VAST would be that you either have to fit one box per TV and that means a total re-cabling in quad shield and a lot of dollars or a head end of several VAST boxes and a string of modulators to pump the analog versions through the crap existing cable system.

Advantage here is that owner doesn't have to pay for new TV's or cabling but eventually all those TV's will die and will new ones down the track have analog tuners in them ?

How many VAST box allocations will there be per address ?

[Guest vtv]

vtv ,your not alone with this electric fence issue.

Although all my area uses UHF ,I still have issues with fences so I pity those like yourself that are trying to get VHF digital in an electric fence region.

I have no magic answer as I suspect there is none ( except banning them but that will never happen or work) ,however the only thing I have found to help is obviously getting the best signal to fence interference position when mounting the antenna.

I use an Unaohm T40a meter and as has been said by M'Bozo , I find the RU count will show bursts when the fence is interfering ,also on the spectrum analyzer,although its not the "real time" high resolution I would expect if I had an AP01 etc, I can still see the interference spikes in between channels and use this is an indicator relative to a desired multiplex to gauge where minimal interference will occur.

Education of the owners of fences can help.Most have now Idea. I have found it helpful as an incentive to get them to "Maintain" them by suggesting that if it is sparking out somewhere that there will not be a useful voltage on the fence to withhold their stock.This generally makes sense to most and also helps justify the whole existence of the fence.(If it ain't work'n ,whats the point of it be'in there) .

Others seem to go by the theory that the stock see the fence and just know not to go near it and simply turn it off when they want to watch something on telly,(bugger the neighbors)

One of MY neighbors strings up miles of white tape and doesn't even have a fence controller connected to it ( unfortunately one of his young calves wasn't quite so knowledgeable and me and my son had to round it up and put it back in the paddock) @#$%

If I have installed a digital antenna system on a rural property and get a call perhaps weeks ,months ,years later that there is Picture brake up ( pixallating) all of a sudden,first question is "do you have an electric fence" ? " Can you turn it off and call me back and let me know if it has or hasn't made a difference."If yes then I leave it up to them to find out where its arcing out.If not then its a service call.

Re : the pub issue

Miles of that shitty brown single shielded air spaced cartwheel crap tacked up right next to the power cabling with splitter after splitter .Every sparky and his dog have added a bit here and there and the owner wants it fixed for a few slabs.

Problem with VAST would be that you either have to fit one box per TV and that means a total re-cabling in quad shield and a lot of dollars or a head end of several VAST boxes and a string of modulators to pump the analog versions through the crap existing cable system.

Advantage here is that owner doesn't have to pay for new TV's or cabling but eventually all those TV's will die and will new ones down the track have analog tuners in them ?

How many VAST box allocations will there be per address ?

At least with the vast boxes we could modulate to whatever channel we like.

The first question I ask when someone describes regular(ever 2 to 3 seconds)pixellation is do you or a neighbour have an electric fence

I think most animals wiill eventually work out a fence isnt on.

I cant help feel the government dropped the ball a bit when deciding we all need digital TV,did anyone at any stage seriously look at impulse noise and electric fence interference to digital.

The half assed approach was to mandate no digital channel below VHF 6 but that is proving to be woefully inadequate.

I was initially very enthusiastic about digital but am finding its creating HUGE headaches in my area.

Sounds like you have worked in a few pubs to have seen the Beer slab cabling you mentioned.

I will fight on regardless(in the trenches)