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60v p-p rf

Posted: Sun Jan 13, 2019 8:12 pm
by arcosine
I put a scope on my long antenna and it reads 60 volts peak to peak RF from local AM stations.

Re: 60v p-p rf

Posted: Sun Jan 13, 2019 10:02 pm
by fotoralf
In the old days, people living near strong medium wave transmitters used to light their gardens with lightbulbs and later fluorescent tubes connected to wire antennas although it was officially a crime. We still have a law against "theft of electrical energy".

Ralf

Re: 60v p-p rf

Posted: Wed Jan 16, 2019 9:33 pm
by Roger
arcosine wrote:I put a scope on my long antenna and it reads 60 volts peak to peak RF from local AM stations.
In the other thread (longwave sensitivity) you mentioned 6 volts P-P and possible damage to your RSP. I posted the safe levels for the RSP there.

Roger

Re: 60v p-p rf

Posted: Thu Jan 17, 2019 1:57 pm
by ON5HB
60Vpp = 10Wpeak!!

That is a lot, how close are the AM-stations? You must be about right under their antenna.

Are you sure this is all coming from the antenna? And not between antenna and grounding or such.

Re: 60v p-p rf

Posted: Thu Jan 17, 2019 7:03 pm
by fotoralf
He wrote in the initial post that he gets 60 Vpp at his scope's input, so presumably with a very high load impedance. I suppose that with a load impedance of 50 ohms the voltage would be far lower.

Ralf

Re: 60v p-p rf

Posted: Fri Jan 18, 2019 2:19 pm
by arcosine
I found that my scope 10v/div setting is not right,oxidized contacts. Its only about 6 v p-p, unloaded, hi Z. Antenna is about 3k ohm impedance.

Re: 60v p-p rf

Posted: Sat Jan 19, 2019 11:11 am
by fotoralf
Ahhh... :)

Ralf

Re: 60v p-p rf

Posted: Sat Jan 19, 2019 8:17 pm
by franko
arcosine wrote:I put a scope on my long antenna and it reads 60 volts peak to peak RF from local AM stations.
As a new oscilloscope owner, I'm curious about the details of how you hooked this up. I know my scope has 1-megohm inputs, so for most RF devices including my antennas it's necessary to add a 50-ohm feed-through terminator. Did this also apply in your case? Also, I'm not sure if I recall the details of your antenna -- is this a longwire, with the measurement between its feed point and ground? Or a dipole?

Re: 60v p-p rf

Posted: Sun Jan 20, 2019 2:30 pm
by arcosine
I used the scope input and the antenna is a 900 ft wire grounded far end at lake, between 5 and 20 feet high, running approximately northwest. Like any loop its directional. About 3k ohm at MF/LF. DC loop resistance s about 50 ohm, mostly from wire, .03 aluminum welding wire. I have ground stakes at both ends and 75 ft of 300 ohm lead into the shack. The matching transformer is 8 turns primary one turn secondary on ft-87A-F core, Also have 30 turns to a 500 pf variable for tuning.

Re: 60v p-p rf

Posted: Sun Jan 20, 2019 5:28 pm
by franko
arcosine wrote:I used the scope input and the antenna is a 900 ft wire grounded far end at lake, between 5 and 20 feet high, running approximately northwest. Like any loop its directional. About 3k ohm at MF/LF. DC loop resistance s about 50 ohm, mostly from wire, .03 aluminum welding wire. I have ground stakes at both ends and 75 ft of 300 ohm lead into the shack. The matching transformer is 8 turns primary one turn secondary on ft-87A-F core, Also have 30 turns to a 500 pf variable for tuning.
Thanks for the info. I was curious specifically how you connect the antenna to the scope input. (I.e. what cable and/or connector are you using between the scope and antenna.) Also, which scope are you using?