i read somewhere in this forum about power lines affecting certain radios. cant find it again. i have fm72mhz radio is that known to have difficulties near power lines? are power lines problems for all radio signals?

It's not the power lines that cause the problems.(well...it kinda is).
It's actually the ceramic insulators(that insulate the wire from its support structure) failing that cause the problem.
Over time, those insulators ware and crack. The wire then starts to make intermittent contact with the metal supports. It's that "arcing"(if you will) that interferes with our signals.

I heard of a guy one time that was able to determine which poll insulators were bad around the flying field. With planes and radios on...(on the ground), and one guy with a "cheapie" plane in the air. He went around to the polls and banged on them with a baseball bat. When airplanes "jittered", they found the bad insulators. They called the power company, a crew came out and replaced that polls insulators... the "case" (in Cluesous (sp) terms) is "solve-ed".

Now I'm not telling everyone to break out the "Louie-ville" and go poll hunting , but it seems like a good idea if a problem is suspect.

-Mustang51

I've done a lot of helicopter flying within a few feet of high voltage power lines and never had a problem.

Tom

The AMA clearly tells you not to do that, for obvious reasons....Why would you intentionally do that? That's pretty STUPID! :stupid:
Just what we need in this hobby. Some JACK A#@ bringing down some towns power grid. I can see the head lines now...

-Mustang51

Mustang, I tried to find the AMS rules that tell me not to do it but my copy didn't have anything.

What I was doing was hovering in a parking lot that had wires overhead. It never seemed to be an issue to me. The radio worked fine. The helicopter had foam blades which could hardly bring down the St Louis power grid. I still fly there occasionally.

Tom

I could be wrong but I always thought that high voltage lines radiated some degree of magnetic field. Some years ago a friend lost a plane after flying over and then dipping behind high power lines, i.e. the power lines were then between the transmitter and the receiver. In my opinion, it is just far better to stay away from high voltage power lines at all times.

my plane was doing loops i couldnt bring it out . after crashing i went to go look for it. the lines were between me and the plane while looking i could hear the hum of the lines and im thinking thats got to be interference. the plane had to be a good 1/4 mile out or better.what kind of range do radios have anyway? the plane must have been in the bottom of the loop when it hit. ripped the main gear clean off. pieces made a line to the plane sitting right side up. kids came out like roaches looking for it. i found it just in time.some old man pulled his minivan off the road and was in the process of making room in the back when i walked up.

first they take my social security then thay want to take my plane. no justice.

I live out of town and very close to several high voltage/tension towers (the ones that travel from town to town, state to state). We fly our models all the time without issue. When I first moved to this home, I pulled out my frequency scanner to check for the possibility of interfernce, NONE!

One of the local clubs was experiencing radio hits, a few years ago and like was mentioned above it was isolated to a insulator on the road about 1/4 mile from the field entrance. We'd smack the guy wire with a sledge hammer and the scanner would wake up! The utility company replaced the insulator and since then no more problems.

We fly in close vicinity of powerlines, and have only had issues with 40 MHz. 35 and 72MHz seem to be unaffected.

Someone told me why 40 is affected but, i dont fly 40, so in one ear and out the other

When I was living in Australia, our local slope site had power lines across the top. No problem, they were behind us as we flew, and nobody was supposed to get too close to them anyway as they ran down the side of the road (and we never fly over roads or houses, do we?)

Landing had to be done across the slope, crosswind and therefore parallel to the road and the power lines. Again, there was plenty of room and it wasn't a problem. But I once saw a plane get caught in a gust while landing, it moved downwind and gained height (it was a good slope!) and drifted towards the power lines. It got to within one wingspan of the lines, and the controls went crazy. I don't think the frequency was an issue, it would have hit any channel at that distance. The plane actually sat on the lines briefly, sliding along with the tail surfaces waving all over the place, then fell off and landed next to the road.

You can bet that pilot kept good separation from the power lines in future!

[QUOTE]Originally posted by mglavin
[B]I live out of town and very close to several high voltage/tension towers (the ones that travel from town to town, state to state). We fly our models all the time without issue. ------------------------------------------------------------------------------------------------------------------------------------------------------ Yes it's true I know first hand! There are also smaller lines that run along side of the runway literaly!! P.S. A model air plane taking out a high tension wire???? I don't think so.

Yes, it is generally a cracked pole insulator or loose hardware that radiates rather than just the flow of AC through the wires.

In relativity dry areas, dirt and dust will cause arcing. Cities like San Francisco have a dedicated wash-team and that's all they do all day is wash live 12KV lines with low conductivity water that is tested prior to pulling the wash trigger!

A dirty or cracked insulator on a 12-60KV line can radiate broad-band interference that reaches into the FM band 88MHz, and above. It can radiate for thousands of feet and completely saturate a receiver.

The power companies still use a lowly AM radio tuned to a blank spot on the dial, usually around 600kHz and walk the pole line. When they find a noisy pole, yes, they hit it with a sludge hammer to see if the noise changes or stops.

For tough cases, they use an ultrasonic receiver with cross hairs in the sight so they can actually identify the offending hardware.

Try the AM radio of some of the poles you suspect. If it's noisy, I guarantee you'll hear it.

Power lines do radiate electromagnetic fields of energy (EMF). I'm sure you've heard of the health concerns of people living in close proximity to these lines, especially the very high voltage lines. So see, this energy can radiate more than a few feet. I'm personally not too concerned about RF interference from these lines, but if there were a mechanical imperfection like a cracked insulator or maybe a non-linear load then this could definitely create a harmonic radiation which could cause a problem for a nearby receiver. No telling what kind of harmonics would be radiating from a problem of that sort, and I'm sure an emission of this sort could travel quite a ways. I think the frequency of power lines is like 60hz, but any problems with the line and then you may have a harmonic radiation which could easily be in the khz or mhz frequencies.

Wade

The EMF generated by a 12KV line is not a problem for our receivers beyond 6 feet. 60KV increases that to 11 feet.

A cracked insulator, dirty insulator or loose or dirty hardware generates a broadband RF signal, not a harmonic, that will cover all frequencies, not just multiples of 60Hz. Do a search on "Spark-Gap Transmitters" and you'll see the mechanics of this signal.

Close proximity to clean power lines generally do not affect our receivers, but bad hardware on the pole does. Up to many thousands of feet.

[QUOTE]Originally posted by 100mph+
[B]No body said anything about a plane taking out a high tension wire???
You may be referring to what I wrote about taking down a POWER GRID. That's something completely different.
Bye the way??? An R\C aircraft most definitely CAN take down a grid if it hits the right wires or transformer. Ever hear of a SHORT CIRCUIT?

Mustang51 is correct. A model can take down a power line. i.e., short it out. So can a large bird or squirrel.

But only for six (6) seconds.

After the short and the stopping of power, the CB or ACB (air-circuit-breaker) tests (trys to supply power again) and unless the object is a steel chain, it gets blown clear of the line and current flows again. The breakers do this twice before completely shutting down the line.

That's why it is not a good idea to handle downed power lines, you never know if and when the breaker will test.

I don't know about calling it a broadband RF signal even though I guess you could say there is a similarity between a power line radiated harmonic and an RF signal. I've always heard the regular power line emission called Power Line Radiation (PLR) or Power Line Magnetic Radiation (PLMR), and the real problem for receivers would occur when there is some sort of line problem which could cause harmonics of varying frequencies which is termed Power Line Harmonic Radiation (PLHR). PLHR can cause interference problems with nearby electronic devices. I've experienced this problem firsthand with communications equipment while near a problematic power line. It's been a while, but I believe that PLHR is the correct term. If I'm mistaken maybe someone will correct me.

Crash_N_Burn,
I just read what you said about Air Circuit Breakers. Where are those located? I know sometimes that a transformer nearby will blow an internal fuse and the COOP guy has to come out to replace it before power will come back on.

just read what you said about Air Circuit Breakers. Where are those located? I know sometimes that a transformer nearby will blow an internal fuse and the COOP guy has to come out to replace it before power will come back on.
-------------------------------------

ACB's are located at the substation (sub). 4KV and 12KV transformers have fuses located near them. A small, quick short will not generally blow the hard fuses in the line, but may trip the circuit breaker at the sub. Line fuses require a hard short for three complete cycles, circuit breakers only one.

Things may have changed a little since I was a power engineer at the PG&E research facility in San Ramon, CA, but power is power, and it has been handled almost the same since the early 1900's.

Thanks for the info.

Your RIGHT,
I can't fly from one farm because there are hi voltage lines near by.
All I have to do is run my finger lightly along the hood and I can feel the fuzzy feeling in my finger tips.
I placed the plane on the ground and turned on the RX and TX and the servos were going nuts.
Why anyone would even think of flying near power lines is beyond me.

Just because you didn't see it in writing does not make it *RIGHT OR SAFE*
You could have taken the power from a small localized area.
Remember that many people have medical needs that run off electric and nothing worse then a person seeing his power kick off while he was on his dialysis machine.
Your not even supposed to fly a kite near power lines

My mistake...
It wasn't the AMA rule book. It's in the "safe operation" section of the manual that comes with your radios.

Still... Kind of a common sense issue.

When all else fails...

-Mustang51

Crash N Burn ,
Excellent points from a man with obvious experience in the field.
As ham radio operators particularly on the LOW bands (160 and 75 Meters ) running AM we have frequently chased down interference using the same portable AM with a ferrite antenna you described . Once we found the source a call to the power company would usually get us relief.

It may be a good idea for people with questionable power lines to "sniff " the area in the same way you described . There is almost always a quiet part of the AM B'Cast band to give a listen for the popping and frying sounds that come from loose joints in the power line hardware,

As you said the problem is usually worse when dry than wet . Kind of the reverse of what one would expect.