60v p-p rf

Useful information regarding antennas for SDR products.
arcosine
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60v p-p rf

Postby arcosine » Sun Jan 13, 2019 8:12 pm

I put a scope on my long antenna and it reads 60 volts peak to peak RF from local AM stations.

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Tony
AA9CC

fotoralf
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Re: 60v p-p rf

Postby fotoralf » Sun Jan 13, 2019 10:02 pm

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

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Roger
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Re: 60v p-p rf

Postby Roger » Wed Jan 16, 2019 9:33 pm

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

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ON5HB
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Re: 60v p-p rf

Postby ON5HB » Thu Jan 17, 2019 1:57 pm

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.

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Greetings,

Bas - ON5HB

fotoralf
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Re: 60v p-p rf

Postby fotoralf » Thu Jan 17, 2019 7:03 pm

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

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arcosine
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Re: 60v p-p rf

Postby arcosine » Fri Jan 18, 2019 2:19 pm

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.

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Tony
AA9CC

fotoralf
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Re: 60v p-p rf

Postby fotoralf » Sat Jan 19, 2019 11:11 am

Ahhh... :)

Ralf

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franko
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Re: 60v p-p rf

Postby franko » Sat Jan 19, 2019 8:17 pm

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?

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arcosine
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Re: 60v p-p rf

Postby arcosine » Sun Jan 20, 2019 2:30 pm

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.

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Tony
AA9CC

franko
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Re: 60v p-p rf

Postby franko » Sun Jan 20, 2019 5:28 pm

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?

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