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Author Topic: 80M vertical  (Read 4387 times)
ZL1BBW
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Posts: 355




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« on: September 27, 2012, 12:27:04 AM »

Now the weather is improving and it is more the time for antenna farming down here.  I have about 28 metres 90 feet of 3" aluminium pipe.

Am looking at putting up a "fat " vertical, fat because I will be putting 4 outrigger wires on the pipe with a standout stay half way up to give it some more rigidity.

Question, should I use the whole 90 feet or it, and tune out the inductive reactance at the base for 80, or would I be better off trimming the length to say 70 feet, at which it still be "long" due to its increased diameter and use that?

Thoughts please.
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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.
GW3OQK
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Posts: 133




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« Reply #1 on: September 27, 2012, 12:52:08 AM »

Wow, best of luck Gavin.
I'd make it long so the RF current into it and the ground is lower. Therefore less power wasted in ground losses. Hope you have a good earth.
73
Andrew
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ZL1BBW
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« Reply #2 on: September 27, 2012, 12:59:08 AM »

It will have a very good earth, especially in the winter down here.  Was thinking that the extra length diameter would help get it closer for use on 160.
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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.
GW3OQK
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Posts: 133




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« Reply #3 on: September 27, 2012, 06:47:53 AM »

Yes, Gavin, it should be formidable on 80.
Any chance of running a thin 28m wire from the top out to one side, even if it slopes down, to make it an inverted L on 160m? My reading of antennas tells me getting the current max in the middle of the vertical part is really beneficial. Having it thick makes it efficient and less critical to tune. Look forward to a sked on 80 or 160 some time! My Inv L is only 14m but I have done the same thing.
73
Andrew
GW3OQK
ex MN R/O. 99% CW on air using straight key.
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K4SAV
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Posts: 1829




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« Reply #4 on: September 27, 2012, 06:48:59 AM »

You might want to take a look at this link to see some of the problems and solutions of putting up a 90 ft irrigation pipe vertical.
http://www.n6rk.com/irrigation.html
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WB6BYU
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Posts: 13040




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« Reply #5 on: September 27, 2012, 08:45:47 AM »

The raising method shown in that link is called the "falling derrick".  I know some hams who
put up a full-sized 160m vertical using a triple falling derrick - using one to raise the next,
etc., until finally getting one that was tall enough to raise the full antenna.

They did manage to drop it 3 times before finally getting it up, but it does work well.

I'd go with as much height as you can get up in the air and keep up.
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NO9E
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Posts: 383




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« Reply #6 on: September 27, 2012, 09:53:09 AM »

Going through EZNEC, it seems that the efficiency of a vertical with 1 mm or 10cm conductor is similar to a fraction of db. Would there be a raising advantage of having partly pipe metal pipe and partly fiberglass pole?

Ignacy, NO9E
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ZL1BBW
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Posts: 355




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« Reply #7 on: September 27, 2012, 01:06:38 PM »

I have been thinking about the issues of rai8sing that length, so many thanks for the link.  I will put either 4 or 6 outriggers on the pipe, near the top and bottom to make the angle 12' and then 2 or 3 sets up along the pipe and put strained wires on the outer ring, to make a fat vertical.  I am hoping that these strained wires will give the whole thing much more strength/rigidity.

As a bi product they will make it electrically longer.

Intend to make a hinge point about 20 feet up, so am effectively only lifting 70 feet.
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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.
N4JTE
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Posts: 1154




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« Reply #8 on: September 27, 2012, 04:38:14 PM »

I would go with a 1/4 wl, the 70 foot length would be more than sufficent, there is nothing to be gained by making the vertical extra long on 80, especially considering the extra weight and support with 20 more feet.
The real neccesity will be the installation of a good ground radial system to acheive an efficent vertical, should be a killer on 80.
Good luck,
Bob
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ZL1BBW
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Posts: 355




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« Reply #9 on: September 27, 2012, 05:09:45 PM »

The ground system....  will put conventional radials down around it, probably 20 or so.

In addition..

1) will run some radials down into a wetland we have on the property.

2) run some down into a stream/mini river the abounds the property.

3) Put a switch in so I can couple the ground system into the extensive earthing network for the electric fence system on the property.

4) in the winter.  I will lay sheets of coro iron out and join them into the system round the base.

Comments?  Thanks  guys n gals ?
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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.
WX7G
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Posts: 5920




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« Reply #10 on: September 27, 2012, 06:54:49 PM »

A couple/few dozen 1/8 wavelength (11 meter) radials will get your antenna very close to ideal.
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AA5WG
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Posts: 494




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« Reply #11 on: September 27, 2012, 07:06:55 PM »

This sounds like a very nice antenna.  You may want to go all out and try elevated radials.

Chuck
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ZL1BBW
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Posts: 355




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« Reply #12 on: September 27, 2012, 07:18:18 PM »

This sounds like a very nice antenna.  You may want to go all out and try elevated radials.

Chuck
elevated is a problem here, we raise beef steers, and they would have to be at least 4m up to get the tractor underneath etc etc, suppose if I was in Texas would say its 4M to get the steers underneath   Smiley.

Will probably stick with ground level.
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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.
N8CMQ
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Posts: 353




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« Reply #13 on: September 27, 2012, 07:43:35 PM »

Hi Gavin!

If you are going to raise such a large, 90 foot mast, here are two suggestions.

The first is, install a radial field of 120 radials of at least 100 feet long.
Rather than put down sheet metal and worrying about bonding issues, radial wires are easter to install with less problems.

Second, guy the mast with eight guys from the top at a 45 degree slope. Half way down with wire, the bottom half with rope. At the half way point, have the wire go back to the base, so you have a skeleton monopole.

I would bet you end up with a 160 to 10 meter antenna with no traps or tuning, provided you can insulate the bottom of the mast from ground.

BTW, Hy-gain used to sell the 2012AA conical monopole which was a 71 foot height antenna that was 3 to 30 MHz bandwidth, a similar design.

That would be one chubby wideband antenna! The nice part would be the inverted cone operation at the higher frequencies.
What would make it better would be to add a wire from each insulator at the middle and running more skeleton wires for the monopole!

Good luck and have fun!
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ZL1BBW
Member

Posts: 355




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« Reply #14 on: September 28, 2012, 12:33:09 AM »

You might want to take a look at this link to see some of the problems and solutions of putting up a 90 ft irrigation pipe vertical.
http://www.n6rk.com/irrigation.html

Thanks for this link, it makes really good reading, but after 35mm of rain last night, things a bit wetter here than in those photos, ah well summer will soon be here.
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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.
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