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[W1JPP]

The context is portable ops

Let’s suppose I wind enough wire for an 80m dipole (1/4 wave on one side). If I want to work 40m and unwind to the 40m resonant length, and the rest of the wire remains coiled on the wire winder, and I secure the wire and then run my rope from the wire winder to my toe off end.

Does the wire “terminate” at the point where it is wrapped in the winder.

[AI5BC]

Does the wire “terminate” at the point where it is wrapped in the winder.

NO

[W1JPP]

Ok. When operating portable IF I’m using resonant dipoles and IF I’m not using a tuner I’ve always had separate wires for 20/40/80. I hookup the appropriate dipole wires for the band I wish to work.

Yesterday I was reading on a commercial antenna seller site - might have been buddipole - they sold a wire winder and indicated just unroll whatever you need to be resonant and then tie it off. The idea being have enough wire for say 80m, but only unroll what you need until resonant.

I assumed anything wrapped may add length, similar to a coil. But it got me wondering if I was incorrect.

[W4AOK]

Maybe the coil was bare wire?

[W1JPP]

I didn’t think it was bare.

These days if I have the space and am portable I just use a wire for 75m ladderline and balun/tuner then coax to rig so I can get on multiple bands.

[AI5BC]

Answer is still NO. How much simpler can it be?

I use a custom-made dipole I named Infinite Dipole. It uses a Capstan to dispense the appropriate length for 6 meters to 80 meters. It will tune any frequency precisely to resonance. The wire I use and others that have copied the design uses insulated copper cladded steel antenna wire.

[WB6BYU]

Does the wire “terminate” at the point where it is wrapped in the winder.

Well, not exactly.

The exact effect does depend on whether the wire is
bare or insulated, as well as how it is wound.

But you probably can find a length where the wire does
resonate on 40m that is somewhat close to the expected
value.   There are a number of commercial versions that
work this way, as well as homemade versions using
plastic wind-up reels sold for camping clotheslines.  I have
a version using a pair of mason's chalk line reels for this
purpose, but haven't had a chance to try them out yet.

The wound wire may act as an end-loading capacitance
(especially when bare wire is used), or as an inductance
(with insulated wire).  While 80m / 40m should work pretty
well, the effects get less predictable as the amount of wire
wound up gets shorter.  For example, winding the ends of
a 20m dipole to reach 17m is likely to require a different
antenna length than winding up an 80m dipole for the same
band.


So the wound wire still has an effect, but with a bit of
adjustment you can usually find a length that will work.

[WA2EIO]

The context is portable ops

Let’s suppose I wind enough wire for an 80m dipole (1/4 wave on one side). If I want to work 40m and unwind to the 40m resonant length, and the rest of the wire remains coiled on the wire winder, and I secure the wire and then run my rope from the wire winder to my toe off end.

Does the wire “terminate” at the point where it is wrapped in the winder.

Sounds a bit like this product that Collins made for the military and Hy Gain also produced; possibly other too?

https://www.qsl.net/n2ckh/HA4000.htm

[W1JPP]

Answer is still NO. How much simpler can it be?

I use a custom-made dipole I named Infinite Dipole. It uses a Capstan to dispense the appropriate length for 6 meters to 80 meters. It will tune any frequency precisely to resonance. The wire I use and others that have copied the design uses insulated copper cladded steel antenna wire.

So I’m confused. Are you saying no as in “not at all will it terminate the antennas length” or “no, it will significantly “shorten” the antenna length”

Because what you seem to work with “infinite antenna” with a capstan to roll or or release wire is doing just that. Lengthen an antenna by rolling out wire or shorten an antenna by rolling wire upon itself.

I recall some time ago reading about some English station that use a capstan and also there is the ham in florida I think - https://tune-a-tenna.com/ - who does this

So it would see wrapping the side on itself will have the effect of making the resonant length shorter. Maybe not exactly as short as cutting the wire, but shorter.

[WA3SKN]

There will be an effect... it might be capacitive reactance, it may be inductive... but there will be an effect.
Now, in a portable situation, why measure?
Spread you dipole between whatever supports you have, feed with twin lead or ladder line, and use a tuner.
Operate on any band you can load into.
And don't forget the possibility of using a loop.  A random loop fed with the same arrangement can do wonders in portable set ups.

-Mike.

[AC2EU]

yeah, i would like to put one of those on an antenna analyzer to see what it looks like on a frequency scan.
That coiled up wire has to be doing something to the impedance, just not sure what.

Maybe it's me, but wouldn't be simple to start with a 20 meter dipole and bring extensions for 40 /80?
Most of my QRP adventures are day hikes, so 20 meters is all I need. I might venture to 40 , but that's it.

[WB6BYU]

Sounds a bit like this product that Collins made for the military and Hy Gain also produced; possibly other too?

https://www.qsl.net/n2ckh/HA4000.htm

There is an important difference between the various military antennas,
where the unused wire is wound up in the center of the antenna, and
various ham versions ("yo-yo antenna") where the far end of the wire
is wound up instead.

Both work, but the lengths for resonance will be a bit different between
the two because the unused wire has a different impact when it is at
the end of the antenna.

In practice, having the unused wire in the center may be preferable
for an inverted vee, where the weight is directly on the support rope,
while the opposite would be true of a dipole supported from the ends.
At least on the lower bands, having the extra wire at the ends of the
wires means you don't have to lower the feedpoint to make adjustments
(as long as the winders could be reached from the ground with the end
ropes untied).  These are minor practical differences.

[KH6AQ]

The context is portable ops

Let’s suppose I wind enough wire for an 80m dipole (1/4 wave on one side). If I want to work 40m and unwind to the 40m resonant length, and the rest of the wire remains coiled on the wire winder, and I secure the wire and then run my rope from the wire winder to my toe off end.

Does the wire “terminate” at the point where it is wrapped in the winder.

Yes.

An example of this type of antenna is the Hy-Gain MODEL H-4000 PORTABLE REEL TAPE DOUBLET ANTENNA. Note that the Hy-Gain antenna reels from the center but it would work if reeled from the ends as you propose. The reel at the end acts as an end loading capacitance. To compensate for that simply wind more wire onto the reel to achieve minimum SWR at your frequency of interest.

http://www.radiomanual.info/schemi/ACC_antenna/Hy-gain_H-4000_user.pdf

[K2WPM]

Yes, I used a yo yo antenna for a year or so.  Bare 18 gauge copper wire.  I wound the ends around small pieces of PVC.  The length is pretty close to standard dipole lengths (so the short answer to your question is yes).  I prefer winding wire at the ends - rather than at the center - because I used it as inverted vee; I could change bands without lowering the feedpoint.  I marked the lengths using painters tape.  I understood the wound wire at the ends to be a lumped inductor .. but since no current flows at end, it's non-impactful.  Best answer, try it out! 
Best: let us know how you make out.
Here's a fun center-wound 'tactical' version.  The structural part looks suspiciously like a Walmart $5 electric cable holder, painted olive drab ...
https://www.eham.net/article/7949
GL,
David, K2WPM

[N8TGQ]

 It doesn't terminate, it resonates. At the frequency it is wound out to.

 I built a "universal antenna system" for portable operating. 2 35' wires and 20' of RG-174. I built a center connector from an old gift card, and an EFHW transformer. All the wire and string winders are made from old gift cards also. The "ears" on the winder corners let me lock the wire at any spot I want. If I hold the winder between my thumb and middle finger at the points on the sides, the wire will spin off quickly without tangling. I have three winders with string to hold up ends and center as needed. I use cotton kite string. It breaks easily if it gets snagged , and will decompose if lost in a tree.

 The 2 35' wires are marked with knots at the resonant points for the ham bands from 10-40 meters using an analyzer. I used knots because paint or ink wore off eventually. Shrink tubing tended to slip out of place.

 Then one wire was marked for the resonant points as a EFHW for 20-10 meters. The second wire was then connected to the first using one screw terminal of the center connector, and that wire was marked for the EFHW resonant points for 30 and 40 meters. I used double knots to tell half wave from quarter wave.

 One wire was then marked at 29' and the other marked for 17' to use as a classic "Random Wire" to use with a tuner.

 I went back later and found points for 6 and 2 meters. 2 meters works good as a vertical dipole, but running the coax off at a right angle to the wires can be difficult. Since a dipole will work well at it's odd multiples, the 40 meter dipole will work at 15m (3x) and 2m (21x). The orientation is wrong for 2m FM, but it will work.

 Then I added a 1 ounce weight for getting string up in the trees, and adapters to be able to match any radio I may want to use, All my radios and antennas have been modified to use RCA plugs and jacks. They're work well, are inexpensive and easy to put on the ends of the coax. They also disconnect easier when you trip over the feedline. Keeps from pulling your whole setup to the ground! I also have a 5' telescoping antenna for putting wires up on the nails everyone puts in our shelters around here. Saves needing a ladder.

 This all fits in a small zippered case I found at the thrift store. I think it was meant to hold diabetic supplies.

 I thought about putting this kit together and offering it for sale for hundreds of dollars, but I'm too lazy. If you want to do it, just send me ten bucks for each unit you sell!

Here's a link to pictures of my kit, if you're interested:


https://drive.google.com/drive/folders/14pZQEYY8TMjefrzggpFPSOuyJjD3cl88?usp=share_link