We got this radio wireless "fence" for extra containment in case our dogs get lose, doesn't really happen much but it is a nice security.
The thing that struck me was the transmitter operates at 18khz RF. Now do I have anything to worry about as far as output transformers picking up the signal (I know they love to pick up 60hz from power transformers.)
The thing that struck me was the transmitter operates at 18khz RF. Now do I have anything to worry about as far as output transformers picking up the signal (I know they love to pick up 60hz from power transformers.)
I know it is a very odd frequency right in the audio band that cought my attention:
See transmitter specs:
Buy PetSafe Wireless Fence - Discount wireless dog fences by PetSafe
The official website and owners manual doesn't spec the frequency, but I have seen this 18khz mentioned several times.
See transmitter specs:
Buy PetSafe Wireless Fence - Discount wireless dog fences by PetSafe
The official website and owners manual doesn't spec the frequency, but I have seen this 18khz mentioned several times.
It all sounds strange to me, too.
As you say, Mooly, 18kHz is allocated for specialized and maritime uses. I wouldn't think any run-of-the-mill terrestrial product could get OK'd for that frequency.
edit: It looks like the system works by transmitting a signal to the collar. If the pet wanders outside the broadcast range, the collar emits a nuisance tone that deters further wandering.
But it does state right there in the specs...Transmitter Specs: Frequency: 18 kHz
As you say, Mooly, 18kHz is allocated for specialized and maritime uses. I wouldn't think any run-of-the-mill terrestrial product could get OK'd for that frequency.
edit: It looks like the system works by transmitting a signal to the collar. If the pet wanders outside the broadcast range, the collar emits a nuisance tone that deters further wandering.
But it does state right there in the specs...Transmitter Specs: Frequency: 18 kHz
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I'm non the wiser really after looking at that. It doesn't tell anything about the method of operation.
The power requirements are pretty high for the transmitter PSU (1800ma was it ?). I guess 18Khz could be used as a base frequency. Wonder what the "aerial" is on the receiver. It it a coil around the collar maybe.
Dunno is the honest answer. If it is 18Khz then it's transmitted as an "RF" signal. The field strength will be very low as you move away from the thing so I guess it shouldn't be a problem in reality. It would be interesting to put a coil/transformer across a scope input and hold it near the transmitter though
The power requirements are pretty high for the transmitter PSU (1800ma was it ?). I guess 18Khz could be used as a base frequency. Wonder what the "aerial" is on the receiver. It it a coil around the collar maybe.
Dunno is the honest answer. If it is 18Khz then it's transmitted as an "RF" signal. The field strength will be very low as you move away from the thing so I guess it shouldn't be a problem in reality. It would be interesting to put a coil/transformer across a scope input and hold it near the transmitter though
18KHz would propagate just fine as RF, but with very limited range for such a transmitter. 90' is probably about right. Seriously doubtful that it would interfere with any sub comunication (typically around 8-9KHz, but hundreds of thousands of watts.) All those cheap "Atomic Clocks" that listen in on WWVB showed up after the Navy gave an old VLF transmitter to NIST which upped their signal strength a passel. Before that it took a big loop or active loopstick antenna to receive the signal in Silicon Valley from Boulder CO.
I'm more inclined to think the device Receiver emits 18KHz to let the dog know he's reached the limit of freedom. Shock collars have taken a lot of flack lately.
Doc
I'm more inclined to think the device Receiver emits 18KHz to let the dog know he's reached the limit of freedom. Shock collars have taken a lot of flack lately.
Doc
No its a shocker, when the reciever (small black box on the collor) gets past 90ft or where you have it set it gives a few warning beeps then starts the shock. They way it works is when not receiver a signal from the transmitter it gives off a shock, it has some safeguards for power outage and what not programmed. But it there isn't an ultrasonic frequency involved, its all RF.
edit: maybe the warning beep is 18khz, and thats where the resalers are getting the number.
edit: maybe the warning beep is 18khz, and thats where the resalers are getting the number.
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Either way the safeguards make sense. Probably confuse the heck out of a dog to get shocked "in the zone", just because the power bumped.
But back to the initial question; yes, if the thing broadcasts 18KHz RF it will get into any electronics inside the field. Just look at how prevalent 60Hz gets in about anything. Part of that of course is it being broadcast by every wire in the house, as well as coming into a local power supply. But magnetic components of a field can be a problem too. HP shfted from a tube rectifier to diode on the later 200CD's they produced because the decrease in transformer field from not running the filament on the rectifier tube actually gave them better specs from 60Hz not getting into other active components.
Doc
But back to the initial question; yes, if the thing broadcasts 18KHz RF it will get into any electronics inside the field. Just look at how prevalent 60Hz gets in about anything. Part of that of course is it being broadcast by every wire in the house, as well as coming into a local power supply. But magnetic components of a field can be a problem too. HP shfted from a tube rectifier to diode on the later 200CD's they produced because the decrease in transformer field from not running the filament on the rectifier tube actually gave them better specs from 60Hz not getting into other active components.
Doc
Seems to me the transmitter itself does indeed operate at 18kHz. Being a low-power fixed-location unit probably gets FCC approval. I'd probably play it safe and place the transmitter as far as possible from my audio equipment. There is also the 6-foot(?) vertical broadcast area you might use to your advantage. I agree it'd be interesting to put a 'scope on a coil just to see what shows up.
That makes perfect sense to me, 18KHz is right in a dog's sensitive area, and inaudible to most humans so won't cause a nuisance to neighbours.
This probably using 18kHz magnetic field (i.e. near field), not true radiated RF. You need a rather large antenna to radiate any useful amount of 18kHz energy, but a simple solenoidal coil can generate a useful magnetic field. The dog presumably can't hear a magnetic field, but the receiver on his collar can pick it up and administer the appropriate stimulus.
Looks like a good way to annoy any neighbour with good high frequency hearing and decent tweeters.
Looks like a good way to annoy any neighbour with good high frequency hearing and decent tweeters.
The US Navy operates a VLF radio transmitter in Cutler Maine, call sign NAA. It operates with a power of up to 2 MEGAWATTS! Back in the 70's and 80's we used their signal as a back up time standard when WWVL was not available. They operated on 17.8KHz at the time, but I believe they have since changed to a different frequency. All of our equipment is now GPS referenced. The real purpose of NAA is communicating with submarines since VLF frequencies will penetrate earth and water. A dog fence with a few milliwatts of power and a small antenna is not going overpower 2 megawatts into miles of antenna.
The dog fences do transmit an electromagnetic waves, not audio. The signal is not audible, but it could be picked up by phono cartridges, guitar pickups and poorly shielded audio equipment. The transmitting antenna is usually a ferrite rod with multiple turns of wire.
There was a dog shocker on the market several years ago that used a buried wire as the "fence". When the dog approached the fence the beeping started. If the dog got closer.....ZAP! That version put a fairly large current through the wire and it did find its way into stereos, answering machines, headphones, and yes guitar amps.
The dog fences do transmit an electromagnetic waves, not audio. The signal is not audible, but it could be picked up by phono cartridges, guitar pickups and poorly shielded audio equipment. The transmitting antenna is usually a ferrite rod with multiple turns of wire.
There was a dog shocker on the market several years ago that used a buried wire as the "fence". When the dog approached the fence the beeping started. If the dog got closer.....ZAP! That version put a fairly large current through the wire and it did find its way into stereos, answering machines, headphones, and yes guitar amps.
The neighbors had one of these electronic fences to keep their Jack Russell Terriers from escaping. The collars were supposed to keep them from barking, but didn't work very well. When they got rid of the female (the troublemaker), most of the barking and escaping stopped.
jeff
There are some major problems with the radio tracking collars which make GPS dog collars a very attractable alternative. There is no question that the cost of such systems is very high. These devices are very new to the arena of pet owners and so this has kept the price very high for the time being.
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