If you isolate it from the DC voltages on the fence, a VLF transmitter in the 1750m unlicensed band from 160 kHz to 190 kHz (LowFER), could do the trick. There is a 1W power restriction and the one obstacle to overcome is a 15m limit on antenna and feedline length. This last may be a show stopper but there might be some workaround, possibly by using a short antenna galvanically isolated from and inductively coupled to the fence with strategically placed repeaters.

Using an appropriate digital mode, I expect you could send messages pretty reliably—but they would be s l o w. Frankly, I am not sure it is worth the effort to try to use the fence. If I was contracted to solve the problem of status reports, I would jut use RF directly and ditch the fence.

There are many ways to do that and which you’d choose would be down to other requirements. In the end I can’t see any advantages of the fence getting involved, what am I missing?

 

What's wrong with a couple of cheap CB-Radios ???
They will easily cover ~2-miles, even when using really bad Antenna designs.

Plain-ole Wi-Fi will scream with some decent, high-mounted, High-Gain-Antennas.
A couple of cobbled-up "Cantennas" would do the job very reliably.

Using the Fence would be a high-maintenance fiasco.
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OK, that puts it all in a different perspective. At that point, as an older cheap used CB radio transceiver was suggested for each end, dispensing with the fence connection and just using digital over-the-air transmission could work, and be more flexible, simpler, and cheaper. Digital keying of a low powered transmitter can be fairly simple.

 

If you isolate it from the DC voltages on the fence, a VLF transmitter in the 1750m unlicensed band from 160 kHz to 190 kHz (LowFER), could do the trick. There is a 1W power restriction and the one obstacle to overcome is a 15m limit on antenna and feedline length. This last may be a show stopper but there might be some workaround, possibly by using a short antenna galvanically isolated from and inductively coupled to the fence with strategically placed repeaters.

Using an appropriate digital mode, I expect you could send messages pretty reliably—but they would be s l o w. Frankly, I am not sure it is worth the effort to try to use the fence. If I was contracted to solve the problem of status reports, I would jut use RF directly and ditch the fence.

There are many ways to do that and which you’d choose would be down to other requirements. In the end I can’t see any advantages of the fence getting involved, what am I missing?

What's wrong with a couple of cheap CB-Radios ???
They will easily cover ~2-miles, even when using really bad Antenna designs.

Plain-ole Wi-Fi will scream with some decent, high-mounted, High-Gain-Antennas.
A couple of cobbled-up "Cantennas" would do the job very reliably.

Using the Fence would be a high-maintenance fiasco.

OK, that puts it all in a different perspective. At that point, as an older cheap used CB radio transceiver was suggested for each end, dispensing with the fence connection and just using digital over-the-air transmission could work, and be more flexible, simpler, and cheaper. Digital keying of a low powered transmitter can be fairly simple.

Thanks folks!
Point is well taken. I am going to do some research on RF options capable of a couple of miles. I think I may have gotten tunnel vision on this project when there are more optimal solutions available.

 

I am going to do some research on RF options capable of a couple of miles.

I have used XBee radios. The high-power version reaches out a long way. Do not use the 2.4ghz versions for outdoor use.
XBee
It wants line of sight. Also they can repeat a signal. We used one every mile along a pipeline.

 

If you isolate it from the DC voltages on the fence, a VLF transmitter in the 1750m unlicensed band from 160 kHz to 190 kHz (LowFER), could do the trick. There is a 1W power restriction and the one obstacle to overcome is a 15m limit on antenna and feedline length.

If you use U.S. Citizens Band Radio, it should be licensed to use one of the frequency ranges intended for remote control. Really.

 

I suggested using an older 23 channel CB radio because the addition of Audio FrequencyShift Keying would be a minimal technical addition. It might even be done with a computer sound card or channel and only require a new interconnection. So it would be vastly simpler. And probably cheap.

 

If you use U.S. Citizens Band Radio, it should be licensed to use one of the frequency ranges intended for remote control. Really.

Speaking from a regulatory point of view, a CB transceiver has very similar problems to my LowFER suggestions vis-à-vis the antenna and feedline limitations. I wouldn’t use it myself.

 

If you want to build something I would strongly suggest looking into LoRa. There is a very good project for handheld messaging that might be good enough but would at least serve as a starting point.

LoRa is very low data rate but has very long range for its extremely low power. It could even be used in conjunction with GPS (possibly built in to the development board) to do position tracking automatically with very small device size and excellent battery life.

It can easily form mesh networks and could even be extended to do location tracking for animals.

 

I was suggesting a wired connection RF link, although certainly a long fence line will radiate some signal. An unused CB channel in a setting that can allow a long electric fence is probably not in a crowded city where there is a lot of CB use. So it would not bother people. Also, occasional short term interference is a typical CB reality, so nobody would care.

 

Speaking from a regulatory point of view, a CB transceiver has very similar problems to my LowFER suggestions vis-à-vis the antenna and feedline limitations. I wouldn’t use it myself.

In the case of licensed Class D equipment, I would just put an antenna at both ends and do away with using the electric fence as the transmission medium.

 

I vote Wi-Fi with 2 "Cantenas" or Helical-Directional-Antennas ........
Direct, Computer to Computer Networking, with very high-speed.
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I vote Wi-Fi with 2 "Cantenas" or Helical-Directional-Antennas ........
Direct, Computer to Computer Networking, with very high-speed.
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Certainly an RF digital link could do the job, unless it needs to be portable But older used CB radios still in working condition cost a lot less, and can indeed cover longer distances, And finding a silent channel is not difficult, really. In addition, packet audio on an empty channel will probably be much more private because very few would even guess what the sound was. And an interesting alternative just came to me, which is to switch off the high voltage pulsing for the duration of communications. not that complex an option, really.

 

2 used Linksys WRT54G Routers $18.00
Cheaper if You check the local Thrift Shops.
They come with external Antenna-Connectors for
easy attachment to high-gain, directional, "Cantennas".
Easy to configure Firmware.
Lots of Custom-Firmware available, if special features are desired, and you're a geek.

Still plenty of support ~20-years later.
I still kept mine, even though I haven't used it in ~10-years.

The only other things that are needed are a couple of Soup-Cans,
some RF-Connectors, and some Coax.

Or, You could just stick it in a big plastic-box on your roof with
twin, homemade, "Windsurfer" Antenna-Reflectors,
although, I don't know if the Windsurfers will reliably cover ~2-miles,
maybe with direct "Line-Of-Sight" between Antennas.

Or, You could get 3 Routers, and set one up as a "Repeater" in the middle, ( very easy to do ).

A "Cantenna" will easily cover ~5-miles with the addition of an old Satellite-TV-Dish.

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I vote Wi-Fi with 2 "Cantenas" or Helical-Directional-Antennas ........
Direct, Computer to Computer Networking, with very high-speed.
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It doesn’t fit the use case, though. The device needs to be carried by a farmer to report status to a central location from time to time. The physical arrangement of a antenna and router is going to be hard to put in a pocket.

 

Why not just use a cell phone. (assuming the location is within an area covered by cell phones.)

Les.

 

RE : Icecat
Try to play with reduced Clapp circuit.
Just take one fast and robust MOSFET like IXFH42N60 or APT6038. Drain to Vcc. Source via the coil and resistor in series to GND. Coil is 10 wounds air core d=15 mm wire thickness 1 mm. Back-loop capacitance is inner parasythic capacitance, no any outer needed. Gate is fed via safety choke - 30 turns over 1 MOhm resistor d=4 mm. Biasing happens 1 kOhm to the gnd and 10 kOhm to Vcc however better one of them be adjustable to get the ideal work-point for given Vcc. From straiht to gate is coming a second serie - serial resonant tank for 10-100 MHz as You want. At Vcc=24 V the capacitor voltage gets near to 5...20 kV depending on capacitor loss factor and permissive reactive power on it. Thus at 5V is rather believable 2 kV may be harvested. More over, using the RF for information it becomes more easy to detect it. I believe 20 MHz will be much for You, Yet I dont now does the Clapp is capable to work on say, 2 kHz. However introducing the classical two-capacitor positive loop, seems, why to not.

However bit red Your task I begin to worry about wrong direction... why not to use any Nordic nRF-024L tablet instead? Distance at least 1 km, or LORA 3 km. Only problem, Youll need the Atmega32 to control this wonderful tablet. costing under 1 USD. Example - https://www.ebay.com/itm/185216053274?hash=item2b1fbcb01a:g:vBMAAOSwZ2FcMGbh&amdata=enc:AQAIAAAA8Kym3VyshsYw6UUO3YVMzz8QFrihZiRJXKDpOtpMRC4E53h0HK9HwaBm4tLmfy5xbYRN07oswunjhcbHq7LhzLy1V2u48fwahUjmcdD0KURbOHB4kTuXOqeji8CkYg+fS5GrycxujLgevKrgcIwO64CZYlfq3uVA+xxLa78VNbsSWcgefewhUI8DXJOzkdPldetH5SQkXIZUkmY2SfofD//i5wxidYLETJIyUbQlk4+Ts0mPCP27Hm3kwvVz4g7YWHr6GKUP79p9YiNlW3YxuSaCPoJOfA4mQUBP1huRWkyFVzyz0SaQ9bA+pyxXu8cfcw==|tkp:Bk9SR8z4k-n-Yg

And here 5 km accessible for 3x larger but still tiny price https://www.ebay.com/itm/1345090730...tnkhZwDMRh8Km1L9n8b1p6S2zIge|tkp:BFBM5Mqd6f5i

 

RE: Yaakov : <<I vote Wi-Fi with 2 "Cantenas" or Helical-Directional-Antennas>>
Most surprizing was that it worked indeed. Last year I had for few month long collapse of the internet signal strength at home.
Thus I added to my 5.8 GHz router two Yagi antennas and I got about 5 km afar with this installation (what is damn much for so high frequency). For targeting used the satellite finder workhead. But then the phone tower was repaired and now I need no external antenna anymore.

 

2 used Linksys WRT54G Routers $18.00
Cheaper if You check the local Thrift Shops.
They come with external Antenna-Connectors for
easy attachment to high-gain, directional, "Cantennas".
Easy to configure Firmware.
Lots of Custom-Firmware available, if special features are desired, and you're a geek.

Still plenty of support ~20-years later.
I still kept mine, even though I haven't used it in ~10-years.

The only other things that are needed are a couple of Soup-Cans,
some RF-Connectors, and some Coax.

Or, You could just stick it in a big plastic-box on your roof with
twin, homemade, "Windsurfer" Antenna-Reflectors,
although, I don't know if the Windsurfers will reliably cover ~2-miles,
maybe with direct "Line-Of-Sight" between Antennas.

Or, You could get 3 Routers, and set one up as a "Repeater" in the middle, ( very easy to do ).

A "Cantenna" will easily cover ~5-miles with the addition of an old Satellite-TV-Dish.

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"Cantenna" may be copywrited by the Heathkit company. They marketed a dummy load under that name for many years, starting long ago. The original is a special 50 ohm resistor in a gallon paint can that is filled with transformer oil. The purpose is to allow adjusting an RF generating device to match a 50 ohm load without radiating any power.
Using a metal can as a part of an antenna is a much newer idea.

 

I think I must have missed every single twist in the various plot changes of this Thread.

Now it sounds like the TS just needs a couple of high-quality FRS Walkie-Talkies.

CB-Radio has to have Antennas that are far too large and unwieldy for portable use,
except maybe for a Golf-Cart, or a Side-by-Side-4-Wheeler.

How was this project ever going to interface with an Electric-Fence ?

What does the "Digital-Bit-Rate" have to do with anything ?

I thought this was going to be for remote "monitoring" of some kind of Sensor.

Well, at any rate,
it certainly made for a diverse conversation.
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