WDAY Towers down

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K9EZ
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WDAY Towers down

Post by K9EZ » Sat Jun 04, 2011 7:13 am

Kent Winrich
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psmerdon
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Re: WDAY Towers down

Post by psmerdon » Sat Jun 04, 2011 4:27 pm

We seem to have a fascination with "tower down" photos. Probably for the same reason people slow down and "rubber-neck" at auto accidents.

It looks to me like there's coax there under the "open wires" - but I can't figure out what's what. I first thought the jumble of wires around the "coax" was catenary wires (nah not taut enough), maybe they're sampling loop lines and the open wires are lighting power (there's a seriously totalled beacon in "radiotower7").

All fascinating viewing and conjecture from half a world away - which is the ideal distance from a downed tower event!

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Re: WDAY Towers down

Post by w4cl » Sun Jun 05, 2011 1:10 pm

The open lines look more like AC power lines not feeder lines, but it isn't really clear what it is. It could be feeder lines with sampling loop line strung from the bottom.

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Re: WDAY Towers down

Post by psmerdon » Sun Jun 05, 2011 4:30 pm

Myself I've never seen an "open wire" line that was just a pair of wires strung like telephone wires - not down here anyways.

The few I saw looked like this. Pardon the crappy photo, taken as a teenager on a Kodak Instamatic.
4GY tower circa 1963
4GY tower circa 1963
They were described by the suppliers as "six-wire open line".
They were a catalog item of the major Australian broadcast manufacturer AWA.
Did RCA have anything similar (AWA products sometimes were "adapted" RCA designs)?

I don't know what the impedance was. Maybe 300ohms??

What would the characteristic impedance of the WDAY "open wire" be as shown? My guess would be 500 to 600 ohms.

Cheers,

Peter Smerdon
Melbourne, Australia.
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Re: WDAY Towers down

Post by Shane » Mon Jun 06, 2011 8:31 am

Only have experience with one site using coaxial open line and it was 220 ohms, IIRC. Six wires: four arranged in a square around a two-wire "center conductor." Then, two runs of "barbed wire," with about 20 times the usual amount of barbs and the barbs closely spaced, running just above the two outer wires on the top of the square for lightning protection/static drain. We'd sometimes find the detached feet of birds stuck to the barbed wire.

Two-wire "balanced" open line impedance would depend on the spacing. In ham radio we usually see 300- or 450-ohms, I think. I'd be surprised to see it in a broadcast installation but I was surprised to see what we see in the photos although we're still in conjecture on just what we're looking at. And, again, my experience is limited.

Could it be a feedline to a standby antenna? There's a station here that maintains a horizontal wire antenna as a backup to its single-tower "main" antenna.

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Re: WDAY Towers down

Post by PID_Stop » Mon Jun 06, 2011 3:02 pm

Here's a more recent photo of open frame line from a station in town:

Image

It's no longer operational, but you can see the U-shaped brackets that are typical for this sort of transmission line.

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Re: WDAY Towers down

Post by NECRAT » Mon Jun 06, 2011 10:58 pm

WSYR and WGY both used that type of line.

I've seen it used in many places, and typically the stations have replaced it with Coax, which was hung on the support poles for the open air line.
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Re: WDAY Towers down

Post by w9wi » Tue Jun 07, 2011 8:12 am

PID_Stop wrote:Here's a more recent photo of open frame line from a station in town:

(duplicate photo removed - DS)

It's no longer operational, but you can see the U-shaped brackets that are typical for this sort of transmission line.

-- Jeff
WSM has a run like this. Thought I had a picture but can't find it -- guess I need to run down there with a camera... I don't know whether it's still in use but offhand I don't recall seeing any coax on the same run.
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Chris from Milwaukee
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Re: WDAY Towers down

Post by Chris from Milwaukee » Tue Jun 07, 2011 11:17 am

I find this open wire transmission line an interesting thing. So far, everything that I have ever seen seems to have a coax encased in a copper pipe. Wouldn't an open line like that have some drawbacks? In an AM application wouldn't it act like an antenna? And how is this thing shielded? And what about interference from external sources, power lines and solar flares and such?

Cool. 8) I found some more interesting stuff about broadcast transmissions that I didn't know before.
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Re: WDAY Towers down

Post by Kelly » Tue Jun 07, 2011 1:18 pm

Ugh.. An angle iron self supporter? High winds and angle iron towers don't mix, probably worse than even tubular steel self supporting towers. Hopefully they'll replace the tower with a solid leg type.

Ya gotta love that photo of the beacon embedded into the ground though..
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Re: WDAY Towers down

Post by Deep Thought » Tue Jun 07, 2011 2:03 pm

Chris from Milwaukee wrote:I find this open wire transmission line an interesting thing. So far, everything that I have ever seen seems to have a coax encased in a copper pipe. Wouldn't an open line like that have some drawbacks? In an AM application wouldn't it act like an antenna? And how is this thing shielded? And what about interference from external sources, power lines and solar flares and such?
Prior to the development of large coax (hardline) these open wire unbalanced lines were used a lot especially on high-power stations. WMAQ (now WSCR) had such a thing in use until the 80's.

The 'hot' wire is on insulators equally spaced inside the four or six grounded wires forming a shield of sorts and functions basically the same way as the coaxial cable you are used to. It actually works well but is very susceptible to things like ice and wind. There is not much radiation from the wires.

Here is a good photo of a high-power version where you can see the similarity to "normal" coax.
http://en.wikipedia.org/wiki/File:Solec ... feeder.jpg
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Re: WDAY Towers down

Post by PID_Stop » Tue Jun 07, 2011 3:24 pm

NECRAT wrote:WSYR and WGY both used that type of line.
Give that man a cigar! My photo is indeed WSYR, looking north toward the center tower.

Deep Thought makes a good point about it being susceptible to weather... the flip side is, damage is relatively easy to repair, especially compared to buried Heliax.

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Re: WDAY Towers down

Post by NECRAT » Thu Jun 09, 2011 1:20 am

Here are two other views of the open air line that Jeff posted of WSYR in Syracuse

Image

Image
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Re: WDAY Towers down

Post by K9EZ » Fri Jun 10, 2011 7:34 pm

There are also open feeder shots in my post about 747 and 1008kHz. But this open feeder, the outside is attached to the tower, and the center is run up the middle, making the tower a feedline as well.
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Re: WDAY Towers down

Post by K4WRF » Sat Jun 11, 2011 6:24 pm

w9wi wrote:
PID_Stop wrote:Here's a more recent photo of open frame line from a station in town:

(duplicate photo removed - DS)

It's no longer operational, but you can see the U-shaped brackets that are typical for this sort of transmission line.

-- Jeff
WSM has a run like this. Thought I had a picture but can't find it -- guess I need to run down there with a camera... I don't know whether it's still in use but offhand I don't recall seeing any coax on the same run.
230 ohm open wire is still there but not in use since 2003, heliax is buried in the ground...

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