The AM Forum

Two questions on open wire line spreaders.

First, is there any sort of market today for open wire spreaders?
(thinking about making some...)

Secondly, it would be a useful archival and informational thing to discuss the pros and cons of different spreader designs, and to post jpegs of various different spreader designs!

Also, are all ceramic spreaders connected to the feedline by some sort of small gauge wire wrap/tie?? (never used 'em!)  ;D

               _-_-WBear2GCR

Hello Bear,

I haven't seen any spreaders available on the market, but I think there would be a great market for them if you were to make them.

As far as I know, the only feedline materials available for hams are coax, twin-lead,  and window line. We know the tremendous advantage window line gives us over coax for using a dipole over all bands, where coax is limited to fundamental and odd harmonics. But the loss due to line attenuation with window line is still much greater than open-wire line separated with spreaders spaced from two to four feet apart.

In the days prior to coax the usual spreader width was six inches, and with no. 12 wire the characteristic impedance Zo was around 600 ohms. However, there is no magic in 600 ohms when the line is being used with a tuner. Consequently, the spacing can be anywhere from two to six inches, with practically zero radiation at HF.

I'm sure that if spacers were available, do-it-yourself hams would prefer real open-wire lines to window lines to obtain the lower loss attendant with the high values of SWR that accompanies the mismatches that occur when using a random length dipole with open-wire line.

I'd like to see you start such an adventure, and I wish you luck if you do.

Walt, W2DU

A further thought for you, Bear. I suggest that you discuss the marketability of feed line spreaders with my personal friend, Press Jones, N8UG, The Wireman. I'd bet the farm that he'd be as eager to sell your spreaders as he is my W2DU baluns. His business address is www.wireman.com, but his personal email address is n8ug@ss.rr.com.

Incidentally, I'm presently using a combination of 300-ohm twinlead and 45-0hm ladder line in both my MI and FL locations. But if you were to make spreaders I'd buy a bunch of them and go back to real open-wire for my feedlines.

Walt, W2DU

You sure that's not,  www.thewireman.com ?

Yep, it's www.thewireman.com. Sorry, I goofed. Some call it old age dementia--I call it 'senior moment'. Thanks for the correction, Bruce.

Walt, W2DU

If you dare to buy from them... there are these.....

http://www.surplussales.com/Antennas/Antennas-9.html (http://www.surplussales.com/Antennas/Antennas-9.html)


But, if you can make them cheaper Bear, I'm sure there's a market.

Plus, I don't see any there for 600 ohm line.....

The Johnson CS2 spreader shown in the link listed above is made of ceramic, which is sorta heavy, and would pull the center of the dipole down unless it was supported at the center.

On one of my previous feed lines I made spreaders out of 1/8" fiberglass cut to 3/8" wide by 2 1/2" long, which were much lighter than ceramic. 

There are also clear plastics that could be used for making such spreaders. IMHO, I believe the more progressive ham community would go for open-wire feeders if light-weight, high-dielectric spreaders were available.

Walt, W2DU

If there is a problem with plastics it is in temperature.
Some plastics don't like cold at all - get seriously brittle.
Other plastics don't like heat - does the open wire ever get hot??
Oh, other plastics don't like UV.

And, I don't have a means to mold plastic... molds are beaucoup expensive for that stuff!

But, I repeat my earlier request for jpegs and drawings of classic spreaders.
And, how does the feeder wire get attached to the spreader??

            _-_-bear

 Don't know da price...


http://www.daburnonline.com/search.aspx?find=antenna


klc

\

Did you look at the link to Surplussales?
Or do you want pictures posted here instead?


Could be wrong, but I believe you use short pcs of wire to hold them in place.... like a "twist-tie".

W7FG has an ad in QST each month advertising open wire line.

I've been using it here for several years since I built a link-coupled balanced tuner.  Seems to hold up FB.

He uses lightweight, black, thinwall tubing.  I think it's the kind used for underground sprinklers.  Each spreader has a slot cut/ground into each end.  The wire is squeezed into that slot.

He uses insulated wire.  I don't think that bare wire would work for that method.

73, Barrie, W7ALW

W7FG sells 600 ohm ladder line. Here are the pics & prices:

http://www.w7fg.net/

I've used Johnson 4 inch ceramic spreaders since about 1968. They will handle up to #10 feed line with #14 tie wire. My present antenna has been up since 1983. I remember Hatry in Hartford sold them .55 each. I space them 30 inches apart. 6 inch spreaders are heavy. I have some but never used them. I guess thay would be good for a lazy H. gfz

Posting images here would be good.
Good archival reference too...

I'm just trying to determine which style is most bestest, and of course if it makes any sense at all to look into what would be required to produce a run of them... them being ceramic, unless a better idea comes along.

          _-_-bear

..

And then there's these...
wb3huz has listed for sale here, in the for-sale section.....

4 inch Johnson spreaders are about 1/2 by 3/8 inch with 2 holes and 2 end slots. They are unglazed. The longer 6 inch Johnson are glazed. There has to be a lot of wet ice on the feedline to take me off the air. I bet  a little voltage on the feedline would take care of that but don't remember the last time I could have needed to. 

I use those.  Over the years I have accumulated a good size collection.

In the past I have used the classic EF Johnson 6" ceramic spreaders, but one problem is that if the antenna is allowed to whip around in the wind, the 6" spreaders tend to break.  I recall one windstorm when I had my dipole strung between two trees; the next day I noticed that every other spreader in the entire line was broken.

I have noticed that some of my Johnson spreaders are glazed and others not, in all lengths.  Maybe one had a choice, with the unglazed versions costing less.  I'll have to look up in some of the old ads to see.

I have made my own 6" spreaders using 1/2" diameter plexiglas (acrylic plastic) rod.  I actually drilled the holes and used a power tool to form the end groove to make them similar to the Johnson spreaders, but next time I may try heating the wire and see if it will simply embed itself in the plastic.  Plexiglas is lighter in weight, less brittle and less prone to breakage than ceramic, and stands up for many years under the UV from the sun.

My present feedline that runs up through the middle of the tower is spaced with plexiglas spacers cut out of 1/4" thick sheet stock, and I have one every 10 feet.  The feeders are tensioned with small turnbuckles to hold them in place between spacers.  I drilled two holes in the spacer and threaded the wires through, and used a soldering iron to melt grooves at the ends of each spacer to fit directly over the tops of the Z-rungs of my tower, and tied down the ends with galvanised steel electric fence wire.  They have stayed in place for over 25 years now, with never a failure.  The only problem I have had is that over time they collect bird shit, since birds like to perch on the tower and antenna,  but it hasn't seemed to affect the performance of the antenna.

Don,
The only time I ever lost a spreader is if it banged against hard. I use #14 tie wire with 5 or 6 wraps on each side and I don't solder them.

In the early 50's we would cut wooden dowel to 6 inch lengths, drill each end and cut a groove on the ends, and then boil them in parafin canning wax until they quit bubbling.  It boiled all of the moisture out of the wood and helped to seal the wood grain from future moisture.  They were pretty light weight and worked very well.  I used to run a pp 250TH rig with 810 modulators and a Johnson KW Match Box on all bands.  Back then I could not afford the commercial spreaders.  I never had a problem with them.  The method was used by a lot of us back then.  One just had to be careful with the boiling wax as it could burst into flames easily.  I did it outside on a hot plate and an old coffee can.  The old ARRL handbooks explain it and also have pictures.
Larry W7IXZ

eHam has an interesting article here [click]. (http://www.eham.net/articles/18879) ;)

I seem to recall that parafin canning wax was mixed 50/50 with beeswax to make a wax solution to seal things  like i.f. transformer coils and rf chokes in early radio equipment.

...i made my spreaders out of  half-inch pvc pipe. light weight, and very durable...there is an article on the web, where the guy uses plastic coat hangers...cheap to buy at the dollar store..just set up a jig, start cutting, drill the holes, and you're done...do a google for homebrew ladder line....tim...sk..

This is the best way to go these days. The W7FG setup is easy and very light. Ceramic is heavy by comparison. But, if you want the old buzzard look and you use the spacer sparingly (every 5-10 feet), the weight becomes less of an issue. I made about 100 feet of line using those Birnbach spacers and used the setup for 6-8 years with no problems.

Steve's correct, W7FG stuff works great.
It is reasonable in price, easy to run, and also easy to repair.
I use it at my QTH on the coast, and its subject to some pretty nasty wind loads, works fine.

I'd be the last one to discourage any one from a business venture, but I'm not sure how much of a market you'll have for the spreaders, esp. when you calculate the cost to tool up and produce ceramic spreaders. I doubt you'll find it an economical venture, in fact, if you calculate your costs of materials, molds, labor, etc. might be cheaper for you to buy NOS spreaders from Surplus Sales of Nebraska! The ham market would pay perhaps $1-2 per spreader, maybe as much as $5, but as the price goes up, your target demographic shrinks. 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. When I explain the advantages, low loss, multi-band use, etc. they see only the difficulties running balanced line vs. coax. The folks who typlcially spend the big bucks on their stations are teh contesters, and most of them have deciated antenas for each band, so balanced line is of little intrest there. There has been somewhat of an awakening in the ham community about balanced line and balanced tuners, but it is a small segment that routinely use that on the air, I just don't see a very lucrative market there. .

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

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.

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.

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

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.

http://www.trueladderline.com/

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

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

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

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-

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.

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

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

..sk..

Why does a Dragster need big tires?

C

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.

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!

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.

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.

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

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.

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

C

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

Fully modulated 100++ ?

C

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.

I guess we are lucky with this little 16 gauge wire!

C

Model the feed point impedance on 160. Next, calculate the R.F. current at the feed point given reasonable power :)

www.youtube.com/watch?v=qzFKGB6qkXs


The easy way to make true open line. If the link doesnt work go to you tube and search N4LQ.  He makes open line using ink pen barrells as spreaders. If you use the Bic stik pens you dont even have to cut them, simply pull out the ink cartridge and remove the plug from the other end . You secure the spreader to the wire using 1 cable tie for each spreader. No more drilling and cutting pvc spreaders and then threading them thru the line. This is the best plan yet for true balanced line.

AC4R

Thats really pretty neat.  It wont last very long.  1 year in az heat those zip ties break. I have tried to use them on all sorts of outside uses. They turn brittle and crack with almost no force. 

That is a really neat idea.. Gotta hand it to the guy

C

THat sounds too much like work  ;D

I did, however, do a sweep of the ant with the HP3577A VNA and an external HP return loss bridge.  While the results aren't valid because I just hooked the feedline directly to the 50 ohm bridge (this wasn't an attempt at a serious modeling, just messing around), around 2 MHz it was way on the right side of the center of the Smithy chart.

Not to nit-pick, but that's the result of UV exposure, not heat.

There are zip ties that are made for outdoor use from plastics that aren't as UV-sensitive.

Personally, I prefer to use fiberglass garden rods. Cut to length, drill through the ends, thread the wires, tie some retainer wires in place, and you're done.

The UV and the heat comes from the same source. The sun.  This is the valley of the sun.  Not to nit pick..

We have UV protected Zip ties here also.  The last 6months to a year. Then they are so brittle they crack with your fingers..

C

I'll have to echo Barrie. I also have the W7FG ladder line/antenna. It wasn't stressed with extreme high winds and ice, but it DID make it through our Western Pa Winter without any problems.

FRED

Its SILV O line tubing.  I think its grean dot from memory

C

Howdy,

That is a great Video.....neat idea.

73
Jack

...just to be a smart-ass, then?

You started it..

C

I have two of these ceramic tubes, about 3/8th inch in diameter and 4 inches long.  No idea where they came from.   Very thin wall (~1/16th?) but they are tough. Not sure what they are made of, too bad I don't have about 50 or so, I could use this guys technique and some RTV to seal the ends/protect the ties and have the Cat's Meow of wire line...

What are garden rods?

How long are they and what diameter? Where do you buy them?

Wonder if they are about the same thing as the fibreglass electric fence posts I mentioned.

Max-Gain Systems has fiberglass rods....

http://www.mgs4u.com/fiberglass-tube-rod.htm (http://www.mgs4u.com/fiberglass-tube-rod.htm)

The following seems reasonable and I'm sure a few of them could be sawed to size and the zip-tie method from the video would work fine!  Has me thinking!

1/4"OD    (9/64" ID)    0.240    1/16"    8 ft. Black     RT-14-964-8    $4.50

$4.50 for 8 feet! 

They are often used for tomato stakes and the like. They are maybe 1/4" diameter. HTe Lowes and  Home Depots of the world sell them.

to get the horsepower transmitted down to the ground!

              _-_-

Yep, those are the ones. About 1/4" to 3/8" dia., green fiberglass. Picture a green arrow shaft about 5 feet high.

I just cut, drill holes in the ends (a vee-block on a drill press is all it takes), and thread them exactly like one would thread open-wire line with ceramic spacers.

Caveat emptor: this came up in a thread a few years back, and someone mentioned they'd picked some up from some home mega-store and discovered they were actually steel rods cast in fiberglass. The ones I got were solid fiberglass, but that was many years ago.

Just wanted to pass that on in case someone was thinking of buying some en masse only to hit that same snag. I would recommend buying one or two to see what they're made of. If they're no good as spacers, you can always find some good use for them.

Why do Big Fat Babies Produce Big Fat Farts....lol.....just because... 8)

73
Jack

It's still a Neat Idea......

What I would question is the substance they mix in with the fibreglass to make it green. If there is no metal inside, I would still cut a piece and run it in a microwave oven for a couple of minutes (along with a small glass of water for safety reasons) and see if it warms up.

The electric fence posts are closer to 1/2" in diameter, and white.  I have never checked them out in the micro, but plan to use them this summer when I re-do my feedline that runs down to the tower.  I just hope they haven't "discontinued" them, per the usual case of commonly available items when I go to purchase them. I should check these for a wire core, too.

That is an excellent point. I never thought of that.

It's a fairly light green, paler than chlorophyll, actually you might call it a "pastel chlorophyll" (if you're a complete sally). Fairly close to the color of lime juice.

Not far from the color of the Statue of Liberty, which is why I'm surprised I didn't think of that.

I know copper is used to make green pyrotechnics, and it wouldn't surprise me if it were also used as a green pigment. If it's cost-effective to make white house paint using titanium for color (and it must be, because they do), it can't be much worse to use copper to make green fiberglass.

Never nuked it, but used it for spacers in feedline and an indoor antenna at Drake TR-4 power levels for several years. When I took it down, there was no discoloration or distortion, which I did check for. Tuning was normal as could be expected, given that the antenna design was unusual and likely very reactive to start with.

Either way, nuke-checking potential spacers is good practice. Since I may be replacing the feedline in Albion this summer, I'll make sure to do that with the next batch of spacer material I pick up (after ensuring they don't have metallic cores, of course).

Everything has to be green these days.

http://www.sourcewatch.org/index.php?title=Greenwashing