Had a learning experience with my welder, just thought I would share, (engine drive)

[k0ua]

James,
You're always teaching me something. That electrical book sounds like a package my uncle was passing around when I was a little kid. My mother wouldn't let me near it, but I think about it from time to time. Now I know how it worked.

Yeah, that was an interesting little book, I have never seen another like it.

 

[dickfoster]

Somewhere around here I kept a defective power supply from piece of networking equipment. That thing wipes out the entire spectrum when it is plugged in. I think if you put a good antenna on it and keyed it on and off you could make long distance contacts with it. I have never seen a switching power supply put out so much Radio Frequency energy. I have no idea what is wrong with it, I just noticed it one day when I turned on my Amateur radio transceiver and noted that all band were wiped out by this noise source. I tracked it down to something in my own house and went to flipping breakers. The supply was still powering the piece of equipment (data switch) but boy was it ever making the RFI.

Switching supplies can be a real beast to get through conducted and even radiated emissions testing. Consider the fact that they work by switching crudely made DC into mostly square waves then try to force them through a transformer. If you analyze square waves you'll find the fundamental and the entire comb of odd order harmonics. The old liner supplies are much quieter and simpler but they sure aren't nearly as efficient as switchers nor are they as cheap.

Basically that's just what we did, we connected a long wire antenna to a spark gap with an interrupter to switch it on and off. Crude but effective. The transformer for the supply was an old neon sign job, 15KV I think.
The town I lived in at the time had a large Western Electric defence electronics plant, radar I think, so about every other house in town had a ham tower in the back yard so that meant an FCC presence and lots of POd hams. LOL Back then there were only 13 TV channels and you only needed three to work.

 

[k0ua]

Switching supplies can be a real beast to get through conducted and even radiated emissions testing. Consider the fact that they work by switching crudely made DC into mostly square waves then try to force them through a transformer. If you analyze square waves you'll find the fundamental and the entire comb of odd order harmonics. The old liner supplies are much quieter and simpler but they sure aren't nearly as efficient as switchers nor are they as cheap.

Basically that's just what we did, we connected a long wire antenna to a spark gap with an interrupter to switch it on and off. Crude but effective. The transformer for the supply was an old neon sign job, 15KV I think.
The town I lived in at the time had a large Western Electric defence electronics plant, radar I think, so about every other house in town had a ham tower in the back yard so that meant an FCC presence and lots of POd hams. LOL Back then there were only 13 TV channels and you only needed three to work.

You might be surprised how many hundreds if not thousands of miles your "signal" was likely heard. I have worked people in Europe from here in Missouri with as little as a half a watt of RF. Of course this was all on one frequency, not broadbanded like that abomination you guys made, but I am sure some of your energy propagated via ionospheric propagation for some distance.
Here is a fun site:
SparkFun Electronics

 

[dickfoster]

You might be surprised how many hundreds if not thousands of miles your "signal" was likely heard. I have worked people in Europe from here in Missouri with as little as a half a watt of RF. Of course this was all on one frequency, not broadbanded like that abomination you guys made, but I am sure some of your energy propagated via ionospheric propagation for some distance.
Here is a fun site:
SparkFun Electronics

I don't think it went very far but it sure did cover the spectrum with pink noise. Remember it was daytime fun for us kids so pretty much just line of sight and a little ground wave action.
Later on we migrated to our making our own AM radio station with a liner amp buried in the attic in case those FCC types with their field strength meters showed up again. I wonder why forbidden fruit always tastes so much better? LOL

 

[k0ua]

I don't think it went very far but it sure did cover the spectrum with pink noise. Remember it was daytime fun for us kids so pretty much just line of sight and a little ground wave action.
Later on we migrated to our making our own AM radio station with a liner amp buried in the attic in case those FCC types with their field strength meters showed up again. I wonder why forbidden fruit always tastes so much better? LOL

Did you ever go on to get you "ham" license.? You do know that it does not require a morse code test any longer? I was first licensed in 1971, so I have been one of "those guys" for about 45 years now. Here is one of my current rigs

 

[California]

You might be surprised how many hundreds if not thousands of miles your "signal" was likely heard. I have worked people in Europe from here in Missouri with as little as a half a watt of RF.

Hmm. I wonder what is the neighborhood effect of my carbon arc heating torch that I occasionally run from my 230 amp AC stick welder? Would that arc - similar to a carbon-arc searchlight - throw off substantial RF interference?

 

[pmsmechanic]

So... Would it be possible to hook up to a live power line using it as an antenna and wipe out all radio communication for a number of miles along a highway? Just asking.

 

[k0ua]

Hmm. I wonder what is the neighborhood effect of my carbon arc heating torch that I occasionally run from my 230 amp AC stick welder? Would that arc - similar to a carbon-arc searchlight - throw off substantial RF interference?

Yes it would be substantial. Just how rich in harmonics the signal would be and therefore how high in frequency the RF harmonics would be would need to be analyzed, but suffice it to say you wiped out radio communication for some distance.

 

[k0ua]

So... Would it be possible to hook up to a live power line using it as an antenna and wipe out all radio communication for a number of miles along a highway? Just asking.

So who is going to climb that pole and hook to a live power line?. And lets say you did survive which is unlikely, how are you going to couple your transmitter to that line? Inductive coupling? Capacitive coupling?

Carrier current radio stations do a similar thing in the AM broadcast band (530 to 1710 khz) but they couple into the much lower voltage(120 volt) side of the line behind the transformer of the high voltage down to the lower voltage. You see these carrier current stations at college campuses and other restricted areas.

The idea is to have a very short range transmitter, usually limited to a few buildings. They do have some incidental radiation though and sometimes can be heard for miles. Theoretically the pole pig transformer works as a large RF choke to prevent the RF from traveling thru it and radiating along the distribution power lines, but the house wiring in the buildings will also radiate.

 

[jaxs]

You fellers are killing me with those stories. I took a peek inside one of those little foil covered books when I was a kid.:shocked: My contribution to this discussion is the day I learned a little bit about high volt power lines and respecting firefighters. A box truck hit a power pole causing lines to fall on the truck. Grass was burning,sparks flying,smoke and just a general fireworks show. The driver was sitting in the cab scared stiff. I about had him convinced that as long as he wasn't touching both truck and ground at same time he wouldn't be hurt. My instructions were to stand on the running board leap through the air to ground. Suddenly there was a voice from behind me that said"do not move one finger until I say so" at the same time a hand on my shoulder pushed me to the ground and same voice said"plant you ***** right here and don't you say another word". After power was cut off,driver safe and order restored,the young firefighter came over,smiled and said get up and come share some water while I talk to you. He explained how a high voltage arc could follow the hapless driver killing him mid-air. BTW,I learned something else that day,sometines a liitle knowledge can be more dangerous than no knowledge at all.