Open Wire Line Spreaders ??

[Steve - WB3HUZ]

A far as market size, well, I'd say small, most hams don't have the time nor inclination to put together individual spreaders on line.

And if they did, it would be easier to work with a plastic spreader like the W7FG type.

[k4kyv]

Years ago I used 450-ohm open-wire TV lead-in.  It consisted of #18 copperweld wire, with little plastic spreaders embedded about every 6-8 inches, with about 1 1/4" spacing. I have used it to feed half wave dipoles, running as much as a kilowatt, and it always seemed to work OK.

It was cheap and plentiful.  This was in the days of fringe-area TV reception, when in small towns far away from major cities, every house had a 50'-100' tower with a TV antenna on top.  I think the selling point of the open wire line was that it was lower loss than ribbon line, superior in getting the feeble signal down the tall tower to the TV set.

The last time I saw the stuff readily available must have been sometime in the 70's or early 80's.

But I always preferred homebrew open wire line.  Sometimes the copper jacket on the copperweld wire in the TV line would break from flexing, and the line became an effective TVI generator.

Speaking of TVI generation, one of the worst cases I ever had with an antenna was when I put up an end-fed zepp at the house in Houston.  The antenna worked as expected, but after the first rain, my signal completely wiped out every TV within a radius of at least a block (this was before the days when everyone has cable).  I used home made plexiglas spreaders and #12 copper wire, but used the first thing I could get my hands on to tie the spreaders to the wire: a small spool of about #20 wire that was somewhat stiff and mechanically perfect for the  job.  The  wire turned out to be zinc plated steel, and as soon as it got wet the zinc reacted with the copper and formed a little diode at each end of every spreader.  I took the antenna back down and noticed that some of the zinc had actually leached onto the copper wire like a plating.  I cleaned the wire with  steel wool to get rid of the zinc deposits, which luckily was not difficult, and bought a spool of small gauge solid brass wire normally used for things like hanging picture frames.  Using the new wire I re-assembled the feedline and never had another problem with TVI.  From then on, I have always paid close attention to the kind of metal hardware touching any conductor in an antenna installation.

[Ed/KB1HYS]

I use those 1/4 inch diameter fiberglass rods sold as driveway markers.  Cut to about 4" in length, and drilled for a snug fit over an insulated wire. A dab of Black RTV to hold them in place. I once tried to use wire wrapped around but that didn't seem to hold the spreaders that well.

[flintstone mop]

KF1Z has some very nice pics of spreaders. Reminds me of my efforts in the early 90's. Everything was overkill and I had a low-to-the-ground dipole with a T368 as the TX and there was never a problem with wires overheating.
#12 or #14 bare wire would be good enough at Ham power levels. I used #8 and that was the overkill part.
The problems were always in the tuner.
Fred

[k4kyv]

One of my first attempts to build open wire line used 1/4" polystyrene rods. I went to a lot of trouble to drill the holes, file the grooves in the ends, and attach the feeders with small pieces of wire.  It worked great, but after about 6 months the spreaders began to turn noticeably brown.  The following year they started to fall apart.  The UV had turned them to a resinous powder.

[N0JEF]

http://www.trueladderline.com/

[ke7trp]

I use this line.  I have no real complaints other then 20 meters wont tune down. I am sure its the legth of my wires though.  I asked them to please make 12 gauge.  Otherwise, I am going to have to take the antenna down and string up 12 myself.

C

[w3jn]

Why do you need 12 ga wire in high impedance feeders?

[K5UJ]

If you figure that each spreader might be good for 12" of line, and the average feed line is say 100 feet in length, that means $50 just in spreaders, not to factor in line costs for the wire.

A far as market size, well, I'd say small, most hams don't have the time nor inclination to put together individual spreaders on lines. I like old time radio gear, but most hams greet me with a blank look when I mention balanced feedline.

Yeah, but 100' feet of decent coax is up there over $50, so I'm not so sure the cost is an issue.   

I remember when I first ran bal. feed a ham I knew swore up and down it was radiating.  He just could not believe that two wires out in the open would not.  I tried to explain how the fields cancel and collapse but he could not wrap his head around that.   There's an educational issue there.  I happen to enjoy the challenge of routing the line but again, bal. line flies into the face of various modern day restrictions--you would not believe how many hams have a problem with bashing out a little window pane and putting in plexiglass with two holes for the line, or making two holes in the side of the house to bring the line through a wall.  Then there's all these people who get worked up over supports out on the lawn holding the line up.   We have a new municipal code here that says all antenna feeds have to be buried.  Of course the idiots who drew it up know nothing about radio.   I already had my bal. line out so I guess I'm grandfathered, anyway, nothing has happened about it here.  Maybe they changed the code because of me    Anyway, your flagpole vertical crowd isn't going to go for bal. line, and unfortunately there are more hams who seem to be caving in and hiding antennas instead of fighting stupid restrictions.

rob

[WA2IXP]

I've made quite a few open wire lines with homemade plastic or pvc spreaders. Small pvc pipe 1/2 or 3/4 cut in half's or 1/4er's , drilled, threaded on wires and tied with small wire. Usually about 4 inch spacing. On 160 mtrs used 6 inch which runs up tower to center of antenna hanging straight down with alittle tension. Not many spreaders needed. Spacing unimportant.   With a little looking around there's plenty of pvc or plastic scrap to use for the taking. Most of our group here  capable of making and erecting the antenna's can make the line easily. A real time saver would be ready made complete line but would be expensive. I've seen it advertised but don't recall where. Anyway, in listening and talking to fairly new hams on 2 meters I've found most don't have the tools or ability to make line or antenna's. I'm not criticizing , really just a comment on today's society. People don't develop basic hands on skills as we used to or had to.  For HF they buy verticals or ready made antennas like G5RV's that both end in coax. Automatic tuners complete the picture. They do work but not too well  depending on band and setup. Were a dying breed of hams that get great pleasure of rolling our own and understanding how it works. Unless the spreaders were 3 or 4 for a dollar or so I'd be too cheap to by them . That's just me of course.
                                                                                                               Jay-

[k4kyv]

I am not a fan of hollow tubes for spreaders.  Critters tend to make themselves at home in the interior.  If you try to seal the ends, moisture condensation collects in the interior.

1/2" solid plexiglass rods are practically indestructible if you are careful not to crack the plexiglass while sawing and drilling. I'm not sure if lexan is available in solid rods, but it is supposed to be mechanically superior to plexiglass and has better dielectric characteristics.  Both plastics are immune to UV.

Another possibility, that I have not actually tried, would be solid fibreglass rods.  These are cheap at farmers' supply stores, sold as temporary electric fence posts.  They  come in about 4' lengths about 1/2" in diameter and are inexpensive.  Solid white, the insulators would even look just like old tyme ceramic spreaders, but would be lighter in weight and less brittle.

[WA1GFZ]

My 1983 #10 feeders with Johnson 4 inch spreaders hanging in.

[ve6pg]

..i've seen guys use plastic coat hangers...cut to length...i use pcv pipr myself...

..sk..

[ke7trp]

Why do you need 12 ga wire in high impedance feeders?

Why does a Dragster need big tires?

C

[Ed/KB1HYS]

I picked up a bunch of those lucite (?) rods used for venetian blinds and curtains.  They should make FB spreaders, easier to deal with than the fiber glass and a bit lighter too.

[ke7trp]

Charlie from trueladder line.com called me and is willing to make the 12 gauge for those of you that dont want to bother with making your own.  I am going to send him a sample wire. He is going to check to see if this will work. If it will, He will offer the complete no splice 160,80 and 40 meter antennas with the line and spreaders for a hell of a cheap price.

I will try one out. The new transmitter is about done.

C

[N0WEK]

Charlie from trueladder line.com called me and is willing to make the 12 gauge for those of you that dont want to bother with making your own.  I am going to send him a sample wire. He is going to check to see if this will work. If it will, He will offer the complete no splice 160,80 and 40 meter antennas with the line and spreaders for a hell of a cheap price.

I will try one out. The new transmitter is about done.

C

Good plan...Thanks!

[k4kyv]

Why do you need 12 ga wire in high impedance feeders?

We are talking about high surge impedance which is not necessarily the same as the actual working impedance of the line.  If the open wire line is working into a load unequal to its surge impedance, it becomes a resonant feeder with standing waves, so the actual impedance (voltage/current ratio) at any given point may vary widely along the length of the line.  Substantial current could occur at the voltage nulls, so you need heavy gauge wire to run any considerable power level.

I have seen the wire in 300-ohm TV ribbon get hot enough to melt the insulation at the high current points when it was used to feed a zepp type of antenna at less than 300 watts.

[W2VW]

Anyone using a short antenna will find plenty of current somewhere in the system.

I put together some #8 feeders in the yard using 2 part epoxy. It was the slow curing stuff and it the wx turned suddenly cold. I wanted to heat the wire so the glue would not be ruined. Out came the large bench supply that I bought at Hosstraders in 1986. One end of the feeders was shorted and the supply hooked to the other. I cranked the supply up to almost 30 volts and the ammeter was reading well over 50 amps or so. I remember the product of volts and amps to equal 1500. 1500 watts outside at 30 degrees F through 200 feet of #8 THHN only warmed it slightly to the touch. I couldn't believe that much power didn't warm the wire much.

Imagine how much R.F. you have to lose before a feeder shows signs of distress.

[ke7trp]

I think lots of wire antenna failures are due to mistuning and or an unbalance.  Stress during tuning ect.. I try to take care with my 16gauge wire.  I made a chart for the KW using the 259B. Then I start at very low power when the transmitter is happy, I raise the power. I have talked for hours on the T3, Ran outside and felt the wire. Its cold.  Maybe I am lucky

C

[w3jn]

Full strap from the GPT-750 into my 75 meter dipole on 160M, the edgewound coil in teh tuna gets slightly warm and I get talkback from the vacuum cap, but the 16 ga W7FG is stone cold to the touch.  The feedline is such that it's at a high impedance point for 75, which would put it at a low point for 160 (hence the ant taps on the coil being only a couple turns from the center).

That's as severe a test as you'll find with uh, "reasonable" power... sometimes better is the enemy of "good enough"- extra weight, wind loading, ice collection, etc.

[ke7trp]

FULL strap T3 does not make this wire hot either. But 4-400s and 304 TLs might

C

[w3jn]

Doubtful... the GPT runs a pair of 4-400s.

[ke7trp]

Fully modulated 100++ ?

C

[Steve - WB3HUZ]

For sure. JN's GPT has BC mod iron in it and will modulate like crazy. A good yeallo into the mic will make the modulator current meter peg.

Fully modulated 100++ ?

C