Long Wire Antenna Performance Questions

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ultravista

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Sep 19, 2012
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Hoping someone can explain why this is happening, so that I may understand, learn, and make a better antenna.

A few weeks ago I ran a 60 foot long wire antenna, 25 feet vertical and 35 feet sloping from the pole to a terminating point in the yard. The mast is ~18 feet of galvanized fence post - the top is PVC. The PVC top has a small screw eye to channel the wire. The wire runs straight up, then slopes down to a point in the hard.

The wire is 24 AWG single pair cross connect wire – connected together at the spool end. The wire spool is simply hung at the wall with about 20-30 feet coiled in the spool.

The antenna was clipped to the RTL-SDR V3 antenna base without the telescoping whip – alligator clipped to the threaded mast. The base sat on the tile floor.

Using the q-branch in SDRSharp, I had broadcast AM overload everywhere throughout the q-branch range. Even on a BC AM frequency, I had overload from other stations. It was horrible. Unusable. The antenna in its current configuration simply did not work.

Compared to a 25 foot long wire thrown over my neighbors tree, the 60 foot long wire was useless. The 25 footer worked well but I thought I could do better.

I bought a Noelec 9:1 balun.

I ran a the same long wire, in the same configuration, through the Noelec 9:1 balun into the RTL-SDR V3. Wow, what a difference the balun makes. No more heavy BC AM overload, a little here and there - the 60 FT wire performs well. The Noelec 9:1 balun turned the useless antenna into something very usable. Here’s where get lost …

If I connect both ends to the balun, one wire to each terminal, signal drops to near zero. WWV at 10.000MHZ is strong and audible with one wire and drops no near-no signal and becomes inaudible with both wires connected to the balun.

When connecting the second wire to house ground (electrical wall plate ground) the BC AM overload comes roaring back. It went back to heavy overload like it was just clipped to the antenna base without the balun.

If I connect a second 25 foot wire to the second balun port, the signal improves a bit – more than just the single 60 FT wire connected to a single terminal.

To summarize, using a 60 FT wire, without the Noelec 9:1 balun, BC AM overload is everywhere. The balun with one wire connected, BC AM overload is suppressed. Connecting the second leg of the pair to electrical ground brings back BC AM overload. Connecting a 25 FT length of wire running to the second port of the balun seems to improve signal – as if the 25 FT wire compliments the 60 FT wire for improved tuning. Perhaps a ground plane?

Questions:
1) What is the balun doing that suppresses BC AM overload?

2) Why does BC AM overload occur when connecting one of the two wires to an electrical ground?

3) Why does signal disappear when connecting both wires to the balun (one to each wire port)?

4) What is the second wire, running in a different direction, doing to improve performance over the single 60 FT wire?

5) Will a ground improve performance, if yes, how do I ground the antenna and/or RTL-SDR V3?
 

ultravista

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Sep 19, 2012
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Is that an intended, or unintended consequence of the balun? Would another 9:1 do the same thing?
 
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