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Messages - ultravista

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61
Equipment / Re: Long/Random Wire with Twisted Pair - Untwist or Not?
« on: September 04, 2017, 1813 UTC »
Josh - thank you for helping - your antenna-FU is strong!

Do you have any idea how this the single wire in series would compare to the pair in series?

Does the fact that it is folded back upon itself many times have any effect?

Also, is there a length you suggest I use for the CAT 5?

A friend had a 600ft dipole - what was the dipole made from?

HF and below are my target frequencies.

62
Equipment / Re: Long/Random Wire with Twisted Pair - Untwist or Not?
« on: September 03, 2017, 1803 UTC »
Josh - is this correct?

I realize the color combinations will differ.

Would this effectively lengthen the antenna electrically? 75 ft * 4 pairs = 300 feet?


63
Equipment / Re: Long/Random Wire with Twisted Pair - Untwist or Not?
« on: September 02, 2017, 2002 UTC »
Is the cable intact or are these individual pairs of wires without any covering? How are you feeding it to the rig?
To put the wires in series I'd solder and insulate each pair at one end, they're color coded so you know wich is wich, then solder the pair to the next in the sheath and continue. The beauty is you can undo it all (the soldering) and change it to compare performance.

Josh, the wires now are without the jacket and in individual pairs. I do have a lot of wire though so I can make a long run with a jacketed CAT5. I will feed it in the SDR via 9:1 unun, or direct to the SDRPlay RSP2 high Z port.

So ... solder the entire bundle @ one end and the individual pairs to 'the next pair' on the other end? Or pair one to pair two, pair two to pair three, pair three to pair four? I'm trying to picture it.

Or one wire to the 2nd, the 2nd to the 3rd, and so-on through the 8 wires - effectively creating one long wire out of all 8?

64
Equipment / Re: Long/Random Wire with Twisted Pair - Untwist or Not?
« on: September 02, 2017, 1724 UTC »
I'd be tempted to feed them in series

How do I do that?

65
Equipment / Long/Random Wire with Twisted Pair - Untwist or Not?
« on: September 02, 2017, 1625 UTC »
I am getting ready to string up another long/random wire, +100 feet. Receive only.

My wire is single pairs from a CAT5 spool (eight wires - four pairs). The individual pairs are twisted together.

If I understand, the potential for the electromagnetic fields to cancel out by the equal and opposite currents (in each wire) is probable as a result of the twist. The purpose of the twist is to keep it from radiating or receiving, correct?

For the antenna, would it be better to separate the pair - leaving a single wire?

Would connecting both ends, effectively making a twisted flat loop, provide a positive or negative result for receiving? Would this be connecting the pairs in parallel or series?

The cable is good and I want to get the best out of it.

To twist or untwist, that is the question ...

66
Equipment / Re: AM Radio Reception Improved by Large Coil of Wire - Why?
« on: September 01, 2017, 0404 UTC »
PS -- Sony Dream Machines can make good clock DX radios, the weakest link being the small loopstick inside. If you use a tuned external loop, you can probably DX with that radio, making up for the small internal loopstick. Many Sonys have the CXA1019 chip, which was fairly generic in many Sony radios but a hot performer. Their ICF-38 DX portable has one in it.

DX, do you mean Broadcast AM only?

67
AM radio reception in my office is terrible, despite being near a window.

I accidentally improved reception by placing a large coil of wire on top of the radio. The wire is ~100 feet of two twisted pairs (400 feet of wire).

The AM reception is noise free and very strong with the coil and noisy and weak without it.

Can someone explain what is happening? Is it mutual inductance, the large coil inducing a magnetic field onto the internal antenna? If yes, is it inducing voltage, current, or both.

I would like to understand why this is happening.

Curiosity led me to try other coils, mostly smaller, with little or no improvement in reception - such as a 25 foot coil of CAT 5 cable and various lengths of power cords.


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