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K4AVL
06-07-2007, 01:05 PM
In making homebrew ladder line for balanced line multiband doublets, has anyone come up with a good spacer material?
Something that can be gotten at Lowes, Walmart etc,
The best homebrew ladder line, from what I've read is insulated 14 ga stranded THHN.
As far as the spacers go, they say UV resistant is preferred.
I've seen a few sites where they use black plastic coathhangers at 4", cut a wire-sized hole and also a slit in the end, and then use glue once sliding the wire into the slit and hole, or else melt the end shut. One guy has retracted recommending the black coathangers as they're not UV resistant.
Other options I see are beige 1/2" CPVC, another guy recommends black ABS pipe cut & then flattened in an oven with heat. Any quick recommendations on this?

KA9VQF
06-07-2007, 02:23 PM
When I was much younger I made some ladder line to use with my Hammerlund receiver, using lamp cord commonly called zip cord. I had to unzip it to use it.

I made the spacers out of strips of oak, scavenged from a discarded pallet, that I covered with varnish. The spacers were around 7 long and thick by wide. The holes are 6 apart on center. I was allowed to use my dads table saw and drill press to make all the spacers. {a rather big deal at the time, I was only around10 or 11 then.}

Once I had the zip cord strung through all the spacers I used a bit more varnish dabbed right on the wire where it came through the hole to secure the wire in the holes.

It didnt take quite forever to get the thing done, it just seemed like it at the time.

I used this ladder line for many years and moved it with me once I moved out of the house into my own place. As with anything you leave outside for a while it got looking a bit ratty. Eventually the insulation rotted off the wire but most of the spacers were still stuck pretty good with the varnish.

Once most of the copper returned to the earth in the from of a green dust I built another length of the stuff, again using strips of oak scavenged from a discarded pallet, but I used clear polyurethane instead of varnish. Im not sure what the 14 gauge wire Im using is I scavenged it too. Most of it has a red plastic insulation on it. It has lasted fine enough for the last few years.

K4AVL
06-07-2007, 02:45 PM
That's a great idea, using wood. I guess the pressure treated screenbead (or 1/4" x 1 lattice-type wood) would work well. I would just have to drill the holes and slide them on, perhaps add a bit of hot glue to keep them in place.
I was also thinking of the clear soft plastic tubing used for hot water lines with fiber re-enforcement, they are PVC but hopefully would last in the sun. Only 3/8" or so but would slide on easily and hopefully last.

K9STH
06-07-2007, 03:08 PM
Any PVC sold in the past 20 years, or so, is U.V. resistant. The pump connections for my swimming pool have been in 25 years next month and are exposed to the hot Texas sun every day. They are showing no signs of any problems.

The small like 1/2 inch or 3/8 PVC pipe is real cheap and will work fine for making spreaders.

There was an article in QST in the late 1950s about amateur radio operators in Hawai'i making spreaders out of chop sticks!

Just remember that there is a formula which gives the impedance of lines which involves the diameter of the wire and the spacing between wires. I will not be back home until tomorrow evening so I don't have that formula "handy". Will try to remember to post the formula again when I get back if you need it.

Glen, K9STH

KI4ITI
06-07-2007, 04:02 PM
Here's a thread (http://www.qrz.com/ib-bin/ikonboard.cgi?act=ST;f=5;t=152874) that I think you'd find relevant to this discussion. Page 2 also includes a post by Glen with the formula he mentioned.

Happy homebrewing!

73
Josh KI4ITI

WC5CW
06-07-2007, 04:04 PM
K4AVI, et al...

In the old days, spacer material was made from wood dowels that were cut to length, baked in an oven for a suitable time period and then immersed in hot liquid paraffin or beeswax for several hours to keep the dowels from absorbing moisture when they were exposed to rain, snow and plain old humidity...Later, other methods were used to seal the wood, including shellac (a poor choice), lacquer (also a poor choice) and linseed based varnish --aka-- spar varnish (a better choice than the preceding but still not perfect)...The reason for all of this was, of course, to preserve the inherent dielectric constant of dry wood which is quite favorable as an insulating material for DC, AC and many RF circuits.

Today's plastic materials offer better dielectric properties and more so when subjected to climatic elements...Acrylic and solid polyethylene are almost the best materials for longevity and constant dielectric performance when subjected to UV and moisture...PVC is close behind and can be obtained considerably cheaper if you can find the right stock dimensions...The ABS plastic as often used in plastic coat hangers has excellent dielectric properties when new but as some have suggested, reportedly doesn't hold up particularly well for long-term exposure to UV...I don't know first-hand but only from what others have reported.

A radio buddy who shares my interest in balanced line sent me some Fiberglas rods having 3/8-inch diameter, each neatly cut about 5 inches in length...I think these are also excellent for use as spreaders...They drill, cut and sand exceptionally smooth...The dielectric constant is nearly equal to ABS and the weight is about equal to that of solid acrylic, polyethylene and PVC, so no disadvantage there.

Except for the wooden dowels and the ABS plastic coat hangers, you may have a difficult time finding the more primo materials...You may have to go to an on-line source such as #McMaster-Carr ( http://www.mcmaster.com )
#
As for construction of traditional ladder line the formula is: Z=276 Log (2S/d), where "Z" is obviously the characteristic impedance, "S" is the center to center spacing between conductors, and "d" is the diameter of the wire used...Dimensions of the variables "S" and "d" need to be in the same units of measure...Technically, it is recommended that whatever wire gauge you choose to use, the spacing be less than 0.01 wavelength for the highest frequency you will transmit on.

For a somewhat interesting and clearly illustrated description of ladder line construction using ABS plastic coat hangers, you may want to visit here:

http://kr1st.com/hfcoath.htm #

FWIW

Bruce
WC5CW

K3WRV
06-07-2007, 04:32 PM
I think the BEST insulators are probably ceramic, but you probably can't find them these days. As CW says, lots of hams used waxed wood, camera film spools, etc. These days, I'd probably use quarter inch pvc/abs (like you use to hook up a sink or toilet) but be sure to give it the microwave test (microwave on HI for about a minute or two and see if they heat up. If they get hot, try something else. Have also heard of hair curlers being used (but they may not exist these days either!)

ME? I just buy ladder line, or good quality TV Twinlead (OK for about 200 W, gets hot above 400W). And use a GOOD tuner! Johnson Match Boxes are highly recommended here! And you can find them used cheaper than new MFJ.

Bob

W5DXP
06-07-2007, 04:46 PM
W7FG sells an open-wire transmission line that uses 1/2 inch thin-wall irrigation tubing for the insulators. It's hard to beat for cost and function.

W2VW
06-07-2007, 05:28 PM
I use plexiglass window replacement material. Saw it with an electric saw with plywood blade. Make a pile of little rectangles about 1" X 7" and drill holes at 6" spacing. The holes are just a little larger than the insulation on my #12 THHN. Thread 2 lengths of wire through all the spacers. String the whole thing up tight between a few trees in the yard, space the spacers evenly at 40" or so and apply 2 part epoxy near the holes. Work the spacer back and fourth so the glue gets in there. Lasts a long time even in bad WX. I just put some back up yesterday that was originally used in 2002.
BTW the impedance of the feedline isn't critical at all in a typical installation so save the math for amplifier homebrewing.

KL7AJ
06-07-2007, 05:29 PM
Quote[/b] (k4avl @ June 07 2007,06:05)]In making homebrew ladder line for balanced line multiband doublets, has anyone come up with a good spacer material?
Something that can be gotten at Lowes, Walmart etc,
The best homebrew ladder line, from what I've read is insulated 14 ga stranded THHN.
As far as the spacers go, they say UV resistant is preferred.
I've seen a few sites where they use black plastic coathhangers #at 4", cut a wire-sized hole and also a slit in the end, and then use glue once sliding the wire into the slit and hole, or else melt the end shut. One guy has retracted recommending the black coathangers as they're not UV resistant.
Other options I see are beige 1/2" CPVC, another guy recommends black ABS pipe cut & then flattened in an oven with heat. Any quick recommendations on this?
We used to use tongue depressors boiled in paraffin. Wooden dowels available at hobby stores are good too.

K0RGR
06-07-2007, 05:39 PM
My dad made them out of wood dowels. He'd cut them to length and then drill holes in them and notch the ends. He used holes to hold a separate piece of wire that is used to tie the feeders to the ends of the dowels. the short piece of small gauge wire would wrap around the feeder wire above and below the spacer to hold the spacer in place.

The dowels were boiled in paraffin wax to make them water resistant. We had fun doing this without blowing up the kitchen - it would be best to do this outside with NO open flame. If you know a candlemaker, they can help you with this step.

AL7N
06-07-2007, 06:53 PM
I've made open wire feeder spacers out of wood, phenolic, plastic, etc, etc, etc. Use what you can get easily. As long as it holds the wires at a consistent spacing it will work fine. Some materials will resist weathering better than others.

AS to spacing of the conductors, it just doesn't matter
for the average amateur installation. anything that suits you from three to six inches will work fine.

Worrying about what the "characteristic impedance" of such a homebrew feedline is a total waste of time...you won't have a length of it long enough to make any difference, and you sure wont have either end of it terminated in whatever might match the characteristic impedance of it even if you did figure it out.

Just build an equally spaced length of line long enough to get from the center of your doublet antenna to the antenna matching device in your shack and quit worrying about it...it will work fine.

WA5KRP
06-08-2007, 02:19 AM
Quote[/b] (w5dxp @ June 07 2007,11:46)]W7FG sells an open-wire transmission line that uses 1/2 inch thin-wall irrigation tubing for the insulators. It's hard to beat for cost and function.
That's from a very smart antenna/transmission line guy.

Also for your consideration..... (http://images.google.com/imgres?imgurl=http://www.reprise.com/ash/clients2/Parts_Shop/images/PS00129.jpg&imgrefurl=http://www.reprise.com/ash/clients2/Parts_Shop/insulators.html&h=52&w=181&sz=5&hl=en&start=3&tbnid=BuZhWw-Xh77slM:&tbnh=29&tbnw=101&prev=/images%3Fq%3Djohnson%2Bopen%2Bwire%2Bceramic%2Bins ulators%26gbv%3D2%26ndsp%3D20%26svnum%3D10%26hl%3D en%26ie%3DUTF-8%26sa%3DN)

I remember when these were plentiful:

http://www.reprise.com/ash/clients2/Parts_Shop/images/PS00130.jpg

I had a ton of those "obsolete" ceramic spreaders given to me but they disappeared from my parents garage while I was away at college (late '60s). #Bummer. #If this guy still has them and you're willing to make the investment, they will hang in the sky until your wire dissolves. #Or you die of old age. #Consider them to be a durable, long term investment, definitely not as volatile as gold.



WA5KRP
Texas

N4KZ
06-08-2007, 05:24 PM
It's easier to tell you what NOT to make the spacers from. This is a true story from 1969 when I got my novice ticket and my Elmer encouraged me to make my own ladder line. He and I thought that ladies plastic hair curlers might make good spacers. (I was 14 at the time and didn't know any better.)

I asked my mother to buy me a couple of bags of hair curlers the next time she went shopping. A few days later, she produced two bags and mentioned that she found them in two colors -- pink and blue. And since she didn't know which color I wanted, she bought a bag of each!

So, I made my open-wire line using the hair curlers, each one wired in place with small gauge wire. I had a very colorful feedline, to say the least. What I hadn't counted on -- because I was not yet wise to the ways of UV damage and temperature extremes -- was that the curlers were made of very cheap plastic. In less than a year, most had crumbled and fallen apart. That led to me switching to coax-fed antennas -- single-band inverted vees and beams.

Today, I feed all wire antennas with commercially made 450-ohm twinlead. The stuff is inexpensive and quite durable. I used to buy the commercially made 450-ohm open-wire line but too many of the plastic insulators broke or the wire slipped out of the snap-in channel in the ends of the insulators. The 450-ohm twinlead now is great, particularly if you buy the stuff with stranded wire which is less apt to break.

This is one situation where I have a hard time figuring out how and why homebrew is better.

73, N4KZ

AG3Y
06-08-2007, 05:57 PM
"RF-Connection"™ in Rockville, MD. sells commercial "window line" in various gauges. I have had some of the stuff for several years, and just added a new antenna with it. I cannot see playing around with building my own (getting lazy in my old age! ) and the performance is everything I would hope it to be! It's just so darn CONVENIENT! http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif

I still love open wire feeders. Now if I could just get a good truly balanced tuner!

73, Jim

W7KKK
06-08-2007, 06:01 PM
I have also heard that using the plastic hangers that Wal Mart sells for 10 for $2 is pretty good and you get many spacers out of 1 hanger and they seem to last.
I have not tried them but the idea was good.

AG3Y
06-08-2007, 06:34 PM
I'd opt for the plastic hangers, too, if I were going to try to make my own feeder. I'm betting it would outlast a lot of other spacer material ( especially the hair curlers! http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif )

73, Jim

N4AUD
06-08-2007, 07:57 PM
"Mini popsicle sticks" from the craft department at Wally World.

KA0GKT
06-09-2007, 04:28 AM
The last ladder line which I made used black plastic film reels (120 or 220, 2-1/4" film used by professionals in Mamiyas, Hasselblads, Rollies, etc) as the spreaders. At the time I worked for the company which owned the largest photofinishing plant under one roof, and they literally had thousands of the things in big cardboard barrels. They sent them out for recycling along with the "One Use" disposable camera bodies. The camera bodies Kodak and Fuji would buy back, the film reels were hauled away for a price, so they were happy for me to take a few hundred home with me for my "Cute" (the plant manager's words, not mine) antenna project. I drilled the reels to pass the wire, then positioned the reels and secured them with a drop of 2-part epoxie. IIRC, I used 22 AWG copperweld wire for the conductors, and placed a ceramic strain insulator at the antenna end of the transmission line.

73 DE KAGKT/7

--Steve

AC0YW
06-09-2007, 09:23 PM
I am building a long transmission line, and bought several plastic coat hangers for the spreaders before I went to the local farm supply store to purchase fiberglass fence posts to support it up to my ridge. four foot of 3/8" fiberglass cost just 99 cents! Use a dust mask and long sleeves with gloves and a fan to blow the dust away from you to stay healthy while you cut and drill the spacers. A "V" block works well in a drill press too. I made a jig to position all the spreaders so all the holes line up and are all the same spacing. I am NOT threading them on the copper weld, I am using UV (black)resistant Panduit tywraps, the kind with the metal tongue to hold the tail. I am using double ended 1/8 " drill bits to drill the fiberglass and a 4" grinder with a 1/8" wheel to groove the ends of the spacers(mark the ends with felt marker for correct distance and grind off the mark at the groove).
kc0dnv

WA5KRP
06-09-2007, 10:04 PM
Quote[/b] (kc0dnv @ June 09 2007,16:23)]I am building a long transmission line, and bought several plastic coat hangers for the spreaders before I went to the local farm supply store to purchase fiberglass fence posts to support it up to my ridge. four foot of 3/8" #fiberglass cost just 99 cents! Use a dust mask and long sleeves with gloves and a fan to blow the dust away from you to stay healthy while you cut and drill the spacers.
GREAT idea! #I anticipate making some 600ohm line and will try your suggestion. #




WA5KRP
Texas

KE5FRY
06-11-2007, 08:56 PM
I'm using 1/2" black PVC irrigation tubing over THHN 14 ga. wire. I found if i drilled two holes through the plastic, very slightly smaller than the wire and then clipped a slot with dikes to the hole from the outside, the tension was great enough to hold it in place without any other mechanisms. It has been up since summer of 2006. It is a long feedline to an inverted V-over 125'. Incidentally, i had to turn some corners and invented a bracket to do so. I took two slices of 1 1/2" pvc pipe, one nestled inside the other like a sandwich and held it together with an eye bolt. Works great and doesn't hurt the wire at all.

K4AVL
06-12-2007, 12:11 AM
Thanks for all the info, guys.
Actually I completed my project about 3 days ago.
Glen, K9STH said that all newer PVC is UV resistant, and my QTH doesn't get but a few hours of sun on that side of the house anyway. So I used the flexible clear 3/8" plastic PVC water-hose tubing which has fiber re-enforcement. These do have a slight bend due to having been curled up, but maintain the spacing nicely, regardless.
I cut about 40 pieces and made the run about 80'.
I could have done with only 60' but I chose this in case I put up another antenna elsewhere later. It loops around a bit, to create the extra length. I made the pieces 2 3/4" wide, drilled holes so the wires were 2" apart. I didn't cut slots on the ends, but, rather, threaded them by hand, then injected liquid nails or silicone at the ends to a point at least 1/4" past where the wries fed through. I used #14 stranded THHN, and at that spacing the impedance is 495 ohms, according to this site:
http://www.cebik.com/gup/gup31.html
It was probably $11 of wire and $5 of PVC.
The main thing they say is to NOT use certain lengths of ladder line like 32' 65', 96', 130', 260', as they are multiples of 1/2 wavelengths of ham bands themselves and cause the feedline to radiate & RF in the shack. Good lengths are 40' 80' and 110', and I used 80' since I needed 60' to reach my 132' doublet (just 25-30' above ground), and made it meander a bit to get there, just to have this "good" length.
In this pic you can see my temporary jig where it goes out the window. I will be replacing that with a coax connection once I get the 1:1 current balun from DX Engineering.

http://viewoftheblue.com/tubeworks/ladder.jpg

At the right is a rope to make a standoff from the house, then you can see the ladder line in the distance heading toward the trees where it makes another left turn which is not visible. The spacers are 2' apart except for a few closer spacers on each end (at window or connection to feedpoint).
The feedline is about 30' above ground.
I had to work the past few days, but on Saturday (from here in NC) I was able to work MO, IN, MS & TX with decent signal reports running under 100W LSB on 40 with a nearly flat SWR in the space of just a few hours.
So that's good for starters, I'm waiting for my first full day off tomorrow that should be fun.

K9ZMD
06-12-2007, 06:01 AM
Fiberglass rods of various diameters are sold at reasonable prices for use as electric fence posts. The 3/8" x 4' rods seem suitable for open wire spacers, and cost about $1.15 each. For example, check out what's available through this web site (http://www.kencove.com/ShopItemIG.php?item=Fiberglass+Posts). A simple search will reveal several other sites for these rods, which also have potential as spreaders for small quads or moxon antennas.

KC7YPJ
06-12-2007, 07:54 AM
I'm cheap and never throw anything away, old credit cards included, chop em up into strips, drill holes 1 size smaller than your wire, clip a notch from the edge to the hole, snap em on and forget about it.

VA3CPM
02-24-2009, 05:23 AM
SIEMENS QF-3 panel fillers!!!

Measure 2 and 1/4 inches of separation.
I am an electrician and have an abundance of these on hand.

They are strong and rigid.

they Also have a notch where 14 Gage to 10 Gage wire fits in just fine.

Wrap it in a few layers of tape and you are good to go.

:D

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