Batboard

i just put up a 20 foot mast with a diamond dual band antenna on it.. nothing special, mounted to the side of the eves with a 4" standoff and in the dirt about 3'...

when i go to plug the RG-8 coax in, i got a tingle, so i pulled out the ole multimeter and measured 33 volts AC from the shield to the ground on the radio... the plug was NOT plugged in the radio at the time... it simply runs out the window, up the pole to the antenna...

what makes this even more bizzare is that the coax for my ten meter dipole has 0v to ground and the cables run along next to each other till they get a good distance from the roof, both radios are plugged into the same power supply, for what its worth...

any ideas? this one is driving me batty!..

thanks!

marc

We didn't drill into a 120v line now did we?

I remember reading something about antenna's and induced current, but its escaping me right now. I am sure someone will have an answer. Are you perhaps on a mountain top or high elevation?

im beginning to wonder, the only place i could be anywhere near a wire is one of the 2 metal screws holding the metal pole to the metal mount.. i guess ill go out there and insulate it just to see.. (the 4" mount is screwed into the wooden eves, but who knows where someone decided to run a wire)

the coax runs direct from the mast, along the roof, into the window

EDIT: Forgot to add, no mountains here, just the flatlands of Florida

You may have a ground fault in the electrical equipment near your antenna. This can be dangerous. I'd hire a good electrician to test for a ground fault and, if found, let the power company know rather quickly.

agreed.. this is an ancient house that has NO 3 wire electrical anywhere in the house, and my deadbeat landlord doesnt seem to care...

the things you uncover in a 50 year old house..

I would certinaly put a good ground rod near the radio or at the base of the mast. You did say the mast goes into the dirt ground. Tie the mast to a water pipe that is in the dirt if one is close.
Do not make the mistake I did once: unscrewed the coax connector from the base radio with one hand on the coax and the other on the cabinet. "B+ to ground..over" the building had a bad elecrical ground and the antenna was grounded at the base of the mast in the ground, 90 volts AC bites!!! I shook off the "bite" and went out to the truck and striped three feet of the shield off a piece of RG214 and grounded the radio cabinet to the water pipe. Oh, and pluged the ac cord back in the wall outlet.

NEVER TRUST the electrical ground until you prove it is ok, test and be safe.

the other thing i thought of last nite, is that the cables go out of the window, and lay flat on the roof, but looking at the way the house is wired, they are laying parallel and just a couple of feet, over the mains that run to the circuit breaker..

i tested some other cables that come in at a different window in the back of the house and there was 0v on them, and to further support this theory, i have an XM antenna just sitting up there, not hooked to anything, and it had 19v on its shield.. im going to move the cables away from where i suspect these wires are, and go from there..

gotta love coupling!

well i found it...

its my Astron RS-20a power supply.. when i put a 4amp on the bench and hook the radio to that, 0.00v on the shield of the cable, hook it back up to the astron and its 26.49v

any ideas what happened to this thing?

As I started to read this, the thought of your equipment being the source of the voltage first poped up. With a new mast, it probably made a somewhat decent ground connection to the earth.

With you saying the house doesn't have the ground wire in the electrical system power system, you found the difference between the coax ground and the equipment leakage. Without the ground on the power supply, I am surprised that you only found 33 volts.

You may try a soft approach with the land lord that he has an unsafe house. The current electrical code was set up to prevent just this type of electrical voltage difference. You now have an unsafe electrical distibution system in the house.

I am kind of surprised that the house hasn't been brought up to code before this. You have a couple of options at this point. The simple one is to just put in a ground rod and run the ground into your equipment.

The more disruptive route would be to contact a local electrician and find out just how this issue is handled in your area. The local electrical inspector is another route to take. A simple call will give you the facts on if or how this should be corrected.

The down side is that if the land lord gets mixed up in this grounding issue, you might be looking for a new place to be mounting your antennas. Don't forget to bring along your bed and pillows.

Jim

well, i tested other outlets and they all were 0v, long story short, it was the surge supressor power strip attached to my PC (it is plugged in the same circuit as the radios)

i removed it, and put in a new one and its 0.00v

my best bet is one of the MOVs in the old supressor went bad or something..

thank god its fixed, and turned out to be that..

Since you don’t have 3 wire ground in your house as you said, you should not use any suppressors at all that try to shunt to ground. Without the ground, the suppressor shunts spikes to your ungrounded equipment case provided it uses a 3 prong plug.

The only safe way to prevent this is by supplying your own real ground to the surge suppressor ground pin.

Nand.