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Author Topic: Gauge of feedline, of antenna  (Read 2993 times)
KM1H
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Posts: 2489




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« Reply #15 on: October 25, 2017, 02:37:30 PM »

Quote
Nah.  Too lossy.  Think phosphor-bronze or clad steel.

Phosphor bronze for sure at the professional and military antennas. The ships I served on used 1/4" and big shore sites likely went 1/2" or more.


Quote
This article addresses the loss in transmission lines rather than the RF resistance of the wire
itself, but it shows the measured losses are about 2.5 times higher for stranded CopperWeld
lines than for the same lines with pure copper conductors on 160m.

So with a decent wire the Copperweld losses can still be tenths of a dB loss.

The good Copperweld is available in 30 and 40% thickness, dont know about some of the schlock sellers.
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WB6BYU
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Posts: 17053




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« Reply #16 on: October 25, 2017, 03:00:42 PM »

As I understand the spec, 37% copper is by area (or by volume), which means that
the coating thickness is about 10% of the wire diameter.

The problem, however, is that, for stranded wire, this is the thickness on each strand,
and that becomes the thickness of the coating on the whole wire.  For a 7-strand wire, this
means the copper is roughly 1/3 of the thickness it would be on solid wire.  Using the
19-strand "Silky" types the copper might only be 20% as thick.


As is the case with feedlines, the difference may be small for dipoles, loops, or other antennas
with a relatively high feedpoint impedance, but for some wire yagis, or an 8JK that can have
very low radiation resistance, it could make a significant difference.
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N3QE
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Posts: 4880




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« Reply #17 on: October 25, 2017, 03:03:04 PM »

Specifically the wire type and selection criteria.  Nothing found, but the feedline is described as parallel copper tubing.  I have a hunch the elements are high tensile steel cable as this picture tells me strength was a priority.

The greenish-blue tint in the second picture is a strong indication that the elements are at least copper on the outside (e.g. copperweld).
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G3RZP
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Posts: 8123




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« Reply #18 on: October 25, 2017, 03:23:31 PM »

For many years, the usual antenna on Marconi equipped ships was 7 strands of 0.029 inch diameter phosphor bronze wire. According to one now long dead Marconi operator I knew, 'aerials'  were often 'lost' in gales, especially in the North Atlantic. The cash they produced as scrap metal paid for several nights with "professional ladies" in places like Port Said, Valetta and Gibraltar....
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AC5UP
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Posts: 4413




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« Reply #19 on: October 25, 2017, 04:13:23 PM »

The greenish-blue tint in the second picture is a strong indication that the elements are at least copper on the outside (e.g. copperweld).

I wouldn't trust the color rendition in that picture as everything has a bit of a tint to it...  Note the slight burple tint of the tower (which I assume is galvanized steel) and how the two white insulators near the center are slightly blueish.  As for the parallel feed lines straight up the middle, I have little doubt their true color is the greenish tint of weathered copper.  I should also remind myself that although we get a good look at the guys near the bottom of the pic that doesn't mean the radiating elements further up use the same cable.

As mentioned in the previous post, if phosphor bronze cable carries a premium price the cost reduction of using steel in the non-radiating segments would be significant for a structure of this size.
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WA3SKN
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Posts: 6496




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« Reply #20 on: October 26, 2017, 06:55:00 AM »

You guys lost the poster a LONG time ago!

-Mike.
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KM1H
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Posts: 2489




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« Reply #21 on: October 26, 2017, 06:46:58 PM »

Quote
The cash they produced as scrap metal paid for several nights with "professional ladies" in places like Port Said, Valetta

I still have very fond memories of our multiple visits to Valletta on a fleet oiler (tanker to landlubbers) which was the only ship in port each time so it didnt turn into a week of barroom brawls as in Marseilles, Valencia, Piraeus, and some others on other seacoasts with multiple ships from the US and other nations.

Carl
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KD8IIC
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Posts: 648




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« Reply #22 on: October 26, 2017, 07:14:11 PM »

   As thin and invisible as you can get away with.
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K7KBN
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Posts: 3473




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« Reply #23 on: October 26, 2017, 09:37:05 PM »

Take a look at https://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt

...and then check the place out with Google Earth.  That hexagonal pattern is visible from quite a way up.  And in surface view, you can "drive" along the east side of the station, near one of the tower bases.  Lots of taxpayer money there -- still being used, it's said, but for just WHAT?
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73
Pat K7KBN
CWO4 USNR Ret.
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