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Re-Inventing the Tape Dipole

Ulrich H. Steinberg (N2DE) on June 3, 2003
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Re-inventing the tape dipole

About 20 years ago I traveled with a Heathkit HW-8 and a Hy-Gain TD-1 tape dipole in my bag, and both saw quite a few exotic locales. The QRP transceiver by now is an Elecraft K1, and like the HW-8 the tape dipole was sold somewhere along the way. I normally use a MP-1 vertical for my portable operations, but often, when I have space for a full-size dipole, I wished that I still had the TD-1. (which also was available in a military version from Rockwell-Collins called, I believe, the HD-4000) I've tried a few modern light-weight incarnations of the reel dipole, and although they work fine none of them had the sturdy reassuring feel of the old TD-1.

When I spotted these chrome clad 50' measuring tapes on eBay, the pair for $13, somehow they just cried out to be made into a tape dipole. The cases are made of metal coated with plastic and quite rugged. It turns out, although the tape looks like shiny bare metal, it is coated with some stuff that is an excellent insulator - so you have to use steel wool to remove it in some spots - but more about that later.

An aluminum U-profile, 3/4" wide and 1/2" high, normally used to protect the edge of plywood, looked like a good choice for a frame to hold the reels. With a bit of handiwork with a metal saw I fashioned the two brackets that hold the tapes. They are bolted together with a 4 1/2" bolt with nylon spacers in between. (all the materials I used are readily available in hardware stores).

The old TD-1 had a screw-down clamp to stop the tape, which also served as the electrical connection to the tape, and the dust and dirt that gathered in that spot rubbed off the markings on the tapes pretty quickly. So it's probably not a disadvantage that these reels have nothing of the sort. I chose to make the actual electrical connection using binder clips that squeeze a short length of grounding strap firmly onto the tape. Since the tape is coated you have to use steel wool to remove the coating over some length around the desired point of contact, and it turns out that this works quite well.

The finished product is definitely not designed for the backpacker, but it conveys the heft and sturdiness that I remember from the TD-1. With its aluminum frame it is probably even more solid than the original. Taking a clue from the original I have attached a laminated frequency-to-length conversion chart to the back. Unlike the TD-1 with its 66' reels the two 50' reels will not permit operation on 80m. However, since I'm rarely ever on 80m and my K1 is not configured for it, that's not something I miss. I believe that similar tapes are available in 100' length, so you could construct this antenna to cover 80m, too. The whole thing looks and feels professional and solid, which was my most important objective.

My construction has a SO-239 connector that directly connects to the antenna without a balun. I felt that an electrically balanced situation is probably not going to occur in the odd locations that this antenna will be used in, and therefore the added complexity of a balun didn't seem justified - the TD-1 didn't have one either. (Although a small balun can easily be added to the construction.)

How does it perform? That's, of course, hard to say since I can't switch to another antenna easily. Stainless steels tapes are not a particularly good material for antennas if you're looking for low resistance material - but then, real wire antennas out there gather a coat of oxidation pretty quickly which introduces some resistive loss, too. Over all the antenna seems to perform quite well - I get into Europe and South America on 20m with 5W quite regularly from the East Coast despite the lackluster conditions. Setup is very simple using the length chart, and my Elecraft K1 has no problems giving me a 1:1 SWR every time. For a total cost of about $25 and a few bruises on my fingers from the metal work I have an antenna that is at least as rugged as the TD-1 and should travel with me for a long time to come. (and this time I'm not going to sell it unless you make me an offer that I can't refuse ...)

Member Comments:
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Re-Inventing the Tape Dipole  
by VA2PHL on June 3, 2003 Mail this to a friend!
I am just curious. is there going to be some inductance in the part that is roll in the tape receptacle? Since the metal seems to be isolated it would seem to me that being roll on it self like that and whit a thin layer og isolation it would act like that? Let say you use the antenna on 10M what would be the effect of inductance if any?

Philippe

VA2PHL
 
Re-Inventing the Tape Dipole  
by N2DE on June 3, 2003 Mail this to a friend!
The tapes have an insulation layer on both surfaces, but it doesn't seem to cover the edges. Since the housing inside is metal that the edges touch the rolled-up part seems to short out. Even if it doesn't do that perfectly there are no ill effects that I can observe. After all the inductance is connected to the feeder line only on one side, it's not that it sits somewhere in the middle like in a trap dipole. The central part of this antenna (with the aluminum frame also connected to one half of it) is certainly not something that approaches theoretical perfection (and I wouldn't want to model it), but for all practical purposes it seems to behave just like a plain old dipole.

73, Ulrich
 
Re-Inventing the Tape Dipole  
Anonymous post on June 3, 2003 Mail this to a friend!
Years and years ago I had one of those Hygain antennas and it worked poorly. From what I can remember, it arced internally if any more than about 25 watts was used. I tried several times to design my own but these kinds of mechanisms seem to be incompatible with any power level above qrp.
 
RE: Re-Inventing the Tape Dipole  
by KA4KOE on June 3, 2003 Mail this to a friend!
Bravo. Good handiwork. The club here uses a plastic version of this with the internal tapes. I don't know who made it, but it does the same thing.

P
 
RE: Re-Inventing the Tape Dipole  
by N0UY on June 3, 2003 Mail this to a friend!
Well Ulrich, I admire your efforts to do something other than purchase something all ready made and proven. The resulting product is very solid in appearance and seems to be well engineered. It's obvious to me than you enjoyed this project and put a good bit of effort into making the structural components. If the resulting antenna works well enough to satify you and fit your needs, that's all that matters. Thanks for sharing your efforts with the rest of us.

Best wishes, Ray N0UY
 
RE: Re-Inventing the Tape Dipole  
by K0BG on June 3, 2003 Mail this to a friend!
This is a very good weekend project. The only thing I'd do different would be to position the tapes further apart and install a balun in between them. Even a F50 would be large enough for 100 watts.

The lack of a balun is the main reason the original didn't work very well especially at the low suspension heights they were (are) usually installed at.

Alan, KBG
 
Re-Inventing the Tape Dipole  
by KC8JX on June 3, 2003 Mail this to a friend!
Ulrich - Very interesting reading. I admire your ingenuity...this is what made hams, hams. Perhaps it does not work expertly or there are some flaws...however, it is very refreshing to see one who still has that drive & desire to think..."Hmmm, I wonder if this would work". Nicely done. Congrats!
 
RE: Re-Inventing the Tape Dipole  
by N2DE on June 3, 2003 Mail this to a friend!
Some more information on power levels, and some improved construction details. The original Hy-Gain antenna ran the connections from the from the tapes to the SO-239 connector inside the plastic housing, and those connections caused arcing at higher power levels. Here the center conductor connects to the tape via an external teflon coated wire - I have actually tried this antenna without arcing problems up to the 160W that my Drake TR7A delivers.

Since I submitted the article I have improved on the clip/braid connector to the tapes. I now use copper plated clips that I bought in an electrical supply store (not sure what they're called - you find them on cables for battery chargers and the like). They have sharp teeth that I filed off, and now the connection to the tape is a nice large copper surface, and counter pressure on the other side is provided by a rubber foot glued to the clip.

I'm trying to talk my friend Piero Begali (http://www.i2rtf.com) into producing a commercial version of this antenna. Not sure that he'll go for it - but since he realized another idea of mine for the ultimate iambic paddle for portable use, may be we'll really have a commercial re-birth of this antenna ...
 
RE: Re-Inventing the Tape Dipole  
by W0FM on June 3, 2003 Mail this to a friend!
Nice job Ulrich! I envy your handiwork capabilities. Perhaps you could find a solvent that would "easily" clean the coating off the full length of the tape. Then, without sanding, the issue of the unused portion being coiled up in the housing would be gone due to direct shorting of the coil along its entire length.

Great creativity!

Terry, WFM
 
Re-Inventing the Tape Dipole  
by KE4ZHN on June 3, 2003 Mail this to a friend!
Now this is COOL! Very nice handy work OM. What a cool way to make a multiband portable dipole. This is the kind of ingenuity that makes ham radio fun. I imagine someone could use a pair of 100 ft tapes and get 80 through 10 with ease if they desired. I think a balun would be a good idea though, as Im sure in a makeshift portable set up, the dipole would be out of balance and your coax will radiate if you dont use a 1:1 at the feedpoint, but even still, its probably efficient enough that the balun wont make a night and day difference except to the purist. This is a very cool idea and you did a fine job constructing it. Enjoy the DX!

73 Rich
 
RE: Re-Inventing the Tape Dipole  
by KA5N on June 3, 2003 Mail this to a friend!
Just think, if you can't find two identical tapes, no problem. Just get one 100 ft tape and one 50 ft tape and make an off-center fed doublet (or windom we used to call them) and feed with TV twinlead.
Allen KA5N
 
Re-Inventing the Tape Dipole  
by AD8A on June 3, 2003 Mail this to a friend!
I've been looking at doing this too, but I have a different way to solve the connection problem. I am thinking about reversing the tapes, soldering the ends to the internal connection, and hanging the reels on the ends - picture an old typewriter ribbon with the attachment in the middle. In fact I bet you could just get a decent balun and make a nice connector to fit right onto where the dipole wires attach. I figure I'll need to come up with a good lock for the reels to make up for the load they'll be carying.
 
RE: Re-Inventing the Tape Dipole  
by WB2WIK on June 3, 2003 Mail this to a friend!
Very nice job!

I've done something similar using two tapes, but to prevent that "heavy center" problem which requires a pole support or similar, I used tapes at the *ends* of the dipole, and fed the lightweight open ends of the tapes. Now, the weight is at the dipole's ends rather than its center, and it's easier to install as a flattop without a center support. I just "lock" the tape position when set, and hoist the whole tape, with rope attached, into a tree at each end. The Stanley (U.S. brand) tape measures lock quite securely and even moderate wind loading doesn't pull the tape position.

Of course, it's not as "neat" a package this way, but seems to work fine.

WB2WIK/6
 
Re-Inventing the Tape Dipole  
by KZ1X on June 3, 2003 Mail this to a friend!
What a nice job you did, Ulrich. Bet you could sell these...

For those who haven't the time or inclination to do as nice a job of workmanship as shown in this article, the Yo-Yo antenna and the smaller 'Radiobugs' version http://www.radiobugs.com are similar in concept, and are commercially available.
 
RE: Re-Inventing the Tape Dipole  
by N2DE on June 3, 2003 Mail this to a friend!
I've looked at the Yo-Yo and have actually bought the one from http://www.radiobugs.com : the radiobugs is by far nicer since it has enough wire to cover 80m and also has an option for a balun. The problem is that the plastic reels are flimsy and that the wire is very fragile and frays out after a short time.

Just talked to Piero, I2RTF, and he has warmed to the idea and will probably produce a commercial version. As always with his products, he will go all the way first class: he'll manufacture light-weight phosphor-bronze ribbons calibrated in MHz and mount them in a custom aluminum oxide alloy frame. That should reduce the weight substantially and solve any resistance problem associated with stainless steel. If you're into CW at all you owe it to yourself to check out his top-of-the-line keys at http://www.i2rtf.com

73, Ulrich
 
Re-Inventing the Tape Dipole  
by W4KWD on June 3, 2003 Mail this to a friend!
Very nice, a great job!
 
RE: Re-Inventing the Tape Dipole  
by N6AJR on June 3, 2003 Mail this to a friend!
Sweet!
 
Re-Inventing the Tape Dipole  
by W9JCM on June 4, 2003 Mail this to a friend!
What a great idea. I love that. I am going on the hunt for a pair at lowes thats a great antenna for suitcase hamming. Thanks for the great idea.
 
RE: Re-Inventing the Tape Dipole  
by K3UD on June 4, 2003 Mail this to a friend!
WAY COOL! True ham spirit!

73
george
K3UD
 
RE: Re-Inventing the Tape Dipole  
by K3UD on June 4, 2003 Mail this to a friend!
WAY COOL! True ham spirit!

73
george
K3UD
 
3dB Loss: Tape Dipole  
by KQ6XA on June 4, 2003 Mail this to a friend!
Ulrich,
Your mechanical design and implementation of the tape measure dipole is beautiful.
Recently, the HFpack group measured the efficiency on 14MHz of a very similar tape measure antenna made by Cortland KA5S. The results were -3.58dB down from a wire dipole. The loss may have been due to RF flowing in the coiled tape measures, but the configuration was slightly different than yours. For more information about the antenna testing, please see the HFpack Pedestrian Antenna Shootout 2002 (Horizontal Shootout) on the HFpack website.
http://www.hfpack.com
 
RE: 3dB Loss: Tape Dipole  
by W0FM on June 5, 2003 Mail this to a friend!
Hey Ulrich,

It's been almost three days....is Piero shipping this product yet? ;-)
 
RE: Piero's Commercial Version  
by N2DE on June 6, 2003 Mail this to a friend!
Don't hold your breath - it'll probably take a couple of months before he gets to it with all his other projects in the pipeline. He's primarily making paddles and keys, but he has a very nice collapsible portable quad (that he never sold so far in the US), and I have suggested to him that he should create a whole line of specialty antennas and add this baby. Keep checking his website at http://www.i2rtf.com - may be he'll surprise us.
 
RE: Re-Inventing the Tape Dipole  
by N9FDE on April 26, 2004 Mail this to a friend!
This is to the guy that had a TD-1 and thought it was junk, You my friend must have had a bad one with something wrong with it, Im sure if you would have taken it apart you would have found the problem was simple to fix, I have had a TD-1 dipole for years and have used it extencivly at high power and have never ever had a problem with it arcing even when wet. I think it was one of the neatest and best designed portable antennas ever made and still can't figure out why they quit making them. Im very sorry you had problems with yours but I think that you are the only person that I have ever heard from that didn't like the antenna.
 
RE: Re-Inventing the Tape Dipole  
by DD3LY on April 26, 2005 Mail this to a friend!
I would recommend to construct such an antenna the other way round: with the rollers at the END and a lightweight center insulator in the MID. The rollers need some mechanism to stop the tape preventing that more tape is pulled when the antenna is strung between trees. The advantages are less problems with weight, isolation or stray capacity at the feedpoint. For QRP and power up to 100W I even would recommend a much more lightweight version: with thin multistranded copper clad (isolated) wire (I have bought this from "The Wireman") and two lightweight rollers you usually use for fly-fishing. These rollers have a stopping mechanim. Three simple (small) insulators made from scrap epoxy circuit board and two pieces of thin black KEVLAR-rope (each 100 feet) do the rest. I am always happy with such a flexible and low weight antenna in my backpack. This is a relatively stealthy antenna and I prefer this low profile way. By the way, the rollers with the spooled wire at both ends work as small capacity hats and do no harm there..
 
Re-Inventing the Tape Dipole  
by KL7AJ on May 30, 2006 Mail this to a friend!
Beautiful beautiful workmanship!
Congratulations!

eric
 
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