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Author Topic: Simple fast question about verticals  (Read 2558 times)
STAYVERTICAL
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Posts: 854




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« Reply #15 on: November 21, 2012, 12:00:46 PM »

6BYU, that's a good idea.

The wire would only have to be about 1 metre long and be in the last (thinnest) section of tubing.
The wire would be kept taut by the tape measure spring, and follow the telescoping sections down neatly.
The only spanner in the works is that I am looking at making it adjustable by motor so that I can try different lengths for various bands.

In a variation of the wire in the top scenario, once the basic structure was working, I thought I would try a twist on it.
The idea is to put a top hat on the vertical with the telescoping wire being drawn to a small cylindrical rare earth magnet at the top.
Once the steel tape measure reaches the very top, it is easily drawn to the magnet.

The magnet would be in a thin cylinder of copper with a brass bolt looking upwards to attach three 1 metre long telescoping rod antennas (radio control type).
The copper cylinder simply slips over the top of the antenna (thinnest tube) weatherproofing it.
A brass wingnut finishes the installation.

I have played around with the magnet idea, and it works ok.
Not sure of the contact resistance, since this part of the antenna has not been prototyped yet, but it should be reasonable.
It should also be usable with the stiff copper wire too, providing a small piece of lightweight steel/tin is soldered on the end.

The paradigm I am following is a modular, "snap together" type of system.
Each module (motor/containing-tube/capacity-hat) will be easily fitted together but not vitally dependent on the other modules.
This way I can experiment with different drive/capacity hat systems without being precisely bound to a particular format.

The "blue-sky" goal I have set myself is to produce a vertical antenna which covers 70cm to 40m.
I understand the problems with the 2m and 70cm bands, but hey!, it's only a problem to be solved.

Thanks again for the interest, and the advice - it is all very much appreciated.

73 - Rob

« Last Edit: November 21, 2012, 12:09:51 PM by STAYVERTICAL » Logged
ZL1BBW
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Posts: 355




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« Reply #16 on: November 21, 2012, 03:37:13 PM »

Just did a search and the stuff is called "atomic Strip"  well thats what it is called now and it on  e thingy bay.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
STAYVERTICAL
Member

Posts: 854




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« Reply #17 on: November 21, 2012, 08:02:19 PM »

Thanks 1DAB,

You seem to be a dab hand at finding stuff!
The box and drive system is finished now using a steel tape measure.
Tomorrow the testing begins on 2m and 70cm, where I think the most difficulty will be encountered.
Then as the antenna gets bigger, the frequency gets smaller in subsequent tests.

I will report how it works on UHF/VHF when the tests are done.
The objective is just to get a low impact frequency agile monopole, not gain etc, so if I get out reasonably I will be happy.

I know this is putting the cart before the horse, but once this project is going well, I will be playing with using the magloop as a tunable reflector.
I have had some good luck with close spaced sloping tuned wire reflectors, but I think an unpowered magloop would be very interesting to try.
The remote ATU will be invaluable here, as the impedance is likely to spike radically when the magloop starts sucking power from the verticals' near field energy.
Only the capacitor motor drive system will be used on the magloop, with induction from the vertical doing the rest.

Perhaps, by just changing the spacing and azimuth of the magloop relative to the vertical it will behave like a vertical beam on 40m to 10m.
Anyway, that's for another day.

Again, thanks for the info, Ebay seems to have quite a bit of the atomic strip around, so that provides another string to my bow if the steel tape/cu wire route fails.

73 - Rob
« Last Edit: November 21, 2012, 08:11:10 PM by STAYVERTICAL » Logged
STAYVERTICAL
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Posts: 854




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« Reply #18 on: November 22, 2012, 12:42:51 PM »

Tried the tape measure vertical out on 2m and 70cm - it was a flop.
The problem is the mass of coiled steel is swamping the bit above the spool.
It would tune up on both 2m and 70cm to some extent, but it was very variable.

One possible solution would be to completely encase the coiled spool in a conductive box, with only the used tape section protruding.
Electrically connecting the emerging tape to the box should make the inside of the box not take part in the radiation - at least that is my take on it.
This would make the box into a type of faraday screen for the spooled tape, so that only the outside of the box and the extended tape would radiate.

It did prove however, that it is quite simple to feed R.F. into the edges of a tape measure without having to take the entire paint off.
The feed contact system is just some copper tabs lightly touching the tape as it emerges from the feed rollers.
The tabs are lightly spring loaded because the tape varies in width along its length to accommodate the taper of the crappie pole.

So it appears the antenna is a keeper - lots of experimenting fun is appearing on the horizon.

Happy experimenting,

73 - Rob
« Last Edit: November 22, 2012, 12:46:41 PM by STAYVERTICAL » Logged
N4CR
Member

Posts: 1653




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« Reply #19 on: November 22, 2012, 03:50:37 PM »

Tried the tape measure vertical out on 2m and 70cm - it was a flop.
The problem is the mass of coiled steel is swamping the bit above the spool.
It would tune up on both 2m and 70cm to some extent, but it was very variable.

One possible solution would be to completely encase the coiled spool in a conductive box, with only the used tape section protruding.
Electrically connecting the emerging tape to the box should make the inside of the box not take part in the radiation - at least that is my take on it.
This would make the box into a type of faraday screen for the spooled tape, so that only the outside of the box and the extended tape would radiate.

It did prove however, that it is quite simple to feed R.F. into the edges of a tape measure without having to take the entire paint off.
The feed contact system is just some copper tabs lightly touching the tape as it emerges from the feed rollers.
The tabs are lightly spring loaded because the tape varies in width along its length to accommodate the taper of the crappie pole.

So it appears the antenna is a keeper - lots of experimenting fun is appearing on the horizon.

Happy experimenting,

73 - Rob


Feed the free end and raise the spool up to lengthen it. No coil at the bottom.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
STAYVERTICAL
Member

Posts: 854




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« Reply #20 on: November 22, 2012, 05:27:54 PM »

Thanks for the suggestion Phil.

I am unfortunately constrained by self imposed design restrictions.
The spool is in a box at the bottom of the crappie pole containing tube.
So the conductor must slide up and down inside the pole under motor control.
This makes moving the entire spool impractical unfortunately.

I did consider feeding the free end of the tape and looping the tape up the inside of the tube like a folded dipole.
It did work, but seems to bind a bit more in the tube than a single layer of tape.

The problem is only on 2m/70cm since the lower spool has much less effect on H.F. and 6m, particularly since much of the spool is deployed at these frequencies.
I will try an insulated box to contain the spool first, and if that does not give good results alone, will try a slotted ferrite suppressor at the spool exit.

It's all good fun anyway.
If it becomes too impractical, I will have to separate the 2m/70m functionality, but it's worth a bit of time playing around anyway.
Some old soda cans are being re-purposed to form the impromptu shield, so cost is minimal.

Thanks for the suggestion,

73 - Rob

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