quote:

Originally posted by selogic:
But in THIS case there are no transmission lines . Or ham radios .

I missed that part. He's either got a distribution line or individual power drop he's near. My comments regarded transmission lines which aren't present here. Doubt that much EMF is created in this situation.

quote:

Originally posted by a1abdj:
Is there any way to check for any of these things without any extravagant equipment?

Well, if it happens only when the trailer is parked there and not anywhere else, and with any batteries completely disconnected, that’s pretty conclusive by itself.

How close is the trailer parked to the transformer? A transformer is basically a big EMF gun.

If you have a multimeter, you can probably get at least some information.

If there is magnetic induction from the power lines or transformer happening, you should be able to measure some AC voltage across the brake light, and if your multimeter has a frequency count setting, it should read 60 Hz. The voltage might be too small for some multimeters to read.

If it’s related to some power company radio communication device, you probably won’t read any AC voltage or get a frequency reading. Multimeters generally don’t sample anywhere near fast enough to measure at radio frequencies.

In either case, LED diode rectification would make the AC waveform asymmetric enough that you would probably also read some DC voltage.

EDIT: I should add, this all assumes the hypothetical induction is happening in the trailer wiring rather than inside the brake light unit or the LED itself (probably a reasonable assumption - bigger loop or longer wires means more induction), and that induction is the actual mechanism rather than some more exotic interaction directly with the LED (no idea, don’t know much about semiconductor physics).

This message has been edited. Last edited by: maladat,

Back in the late 40s and early 50s a TV station in Dayton Ohio operating on VHF put out so much power their programs could be seen in some South states. And it did cause plorescant bulbs in homes within blocks of the transmitter to light up some. The FCC made the station cut back the power output as more stations came on.

quote:

Originally posted by maladat:

quote:

Originally posted by radioman:

quote:

Originally posted by selogic:
I hate to burst some of yall's bubble , but I spent most of my 40 yr career with power companies working in high voltage substations . The voltage in some of them was as much as 550,000 volts and the buswork was very low in some of them . Obviously we had LED's on vehicles , trailers , and tons of them on equipment indicating lights . I never saw an LED light up from induction , static , or anything else like that.

Yeah, I see what you mean. We've covered how the mag field from the current in power lines could send the power, but for the LED to light, the trailer end of things (LED, Etc.) would need a complete circuit for current to flow through the LED. Much like the secondary circuit on a transformer with weak coupling. I don't see that we have that necessary complete circuit loop, unless I missed something in how the trailer wiring was described. .

For a (comparatively) very small amount of power, there are circumstances where you either don’t need a closed circuit at all or where a very high-impedance path in a device that would normally not be considered a closed circuit is good enough.

After all, a typical radio antenna is an open circuit supplying a tiny amount of power as input to an amplifier.

Actually an antenna is not an open circuit. I assume you meant an elementary dipole which looks like an open circuit at DC. But at RF, an antenna is a transducer interacting with the impedance of free space, and as such has a radiation resistance of about 73 ohms (assume a dipole) at it's resonant frequency. This radiation resistance holds true whether the antenna is receiving or transmitting.