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virtical dipole




 
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ab3al
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« on: October 27, 2007, 09:09:22 AM »

well The antennas have been down for about a week now.. we had a big wind storm while i was out of town on business.  My back yard is a 20x100 foot lot.. A townhouse with a decent yard for a townhouse.  I have been supporting a 80 meter full loop from 2 10 foot poles on the roof about 18 ft apart and 2 60 foot telescoping channelmaster (cua mau) masts at the far end.  Did Imention i forgot to guy them.  well we had a storm that brought 4 water spouts about 1/5 mile offshore  thats about 1 mile from my house.

the question.  I am gettin frustrated trying to keep wire up and in my hood  (no antenna restrictions) and a hoa that does not have control over my half of the hood (2 different builders and a county blunder lol).  I have been looking at several verticles.  Yeah i know low angle of radiation is best for am local stuff.  but most of you guys are at least 500 miles out.  Radials are my sore spot.  I actually have a machine that digs a trench 2 inches deep burries up to rg11 thick wire and backfills.. Invisible dog fence install machine.  Digging aint the problem  its the 20x100 yard. behind my yard is a stretch of woods owned by the state bordering a highway that i could use.  this would give me radials in 2 directions.

Now the real question.  In nec I modeled and figuredt that with 30 radials 40 foot long in 2 directions with the 43 foot zero five vertical and a homemade base load the antenna will be about 80 percent efficiant but the ground losses will be about half.  Elevating the radials is not really an option because of kids and pets that wander the woods.

When I modeled a 50 foot vertical dipole 2 feet off the ground with off center loading on 80 The efficiency of the ant still looked to be aobut 80 but with minimal ground loss no radials.   AM I MISSING SOMETHING.  Other than the mechanical issues and narrow bandwidth.  I know force 12 makes one like this with both capacity end hats and center loading  but its 800 bucks shipped for 80 meters. 

Is anyone else doing something like this In the forum

testing begins on 20 meters if it goes well Ill move to 40.  for 80 emt wont work ill have to order aluminum

73
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ab3al
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« Reply #1 on: October 27, 2007, 09:11:27 AM »

a typo  High angle radiation is best for local stuff
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W8EJO
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« Reply #2 on: October 27, 2007, 09:50:09 AM »

Try this:

http://www.cebik.com/gup/gup39.html

You could top & bottom hat to stretch to 75.
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Terry, W8EJO

Freedom and liberty - extremist ideas since 1776.
W8EJO
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« Reply #3 on: October 27, 2007, 11:51:15 AM »

Also try a 45' x 45' center fed (with open wire/ladder line) inverted L. It will load up on 80 - 10 with a good tuner. Try to get the bottom at least 5' off the ground (total height = 50').

I made a 90' x 90' version at my MI cabin & it worked quite well on 160 & up.

You'll have to play with feed line length.

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Terry, W8EJO

Freedom and liberty - extremist ideas since 1776.
Tom WA3KLR
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« Reply #4 on: October 27, 2007, 12:43:26 PM »

Well, a center-fed dipole as long as you can get (80-100 ft.) say 30 feet high or higher and ends coming down vertically to 10 foot off ground, fed with ladder line and a good 160 tuner will work 160 o.k., very good on 75 and 40 meters, and the 5 MHz. channels too.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
The Slab Bacon
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« Reply #5 on: October 28, 2007, 10:08:06 AM »

Mike,
         Are you talking about a vertical dipole or a vertical radiator?? A true vertical dipole would be center fed, and not require ground radials. A vertical radiator sitting on top of a buried ground radial system is actually a "ground plane" antenna.

With a vertical antenna and its low angle of radiation you would be piss weak to anyone close in. Why not try putting up some kind of balanced dipole out in the woods. Feed it with ladder line to a remote tuner in another tree, then run buried coass from the remote tuna into the shack.

build a remote tuna with motor driven caps or inductors and pipe the dc power out to them through the same coass as the feedlind. It is doable with the right combination of chokes and caps to isolate the dc from the rf. This would give you the best of both worlds.

Or try putting up an antenna like mine. It is only 60' long!! remember it doesnt have to be resonant (at 50 ohms) to work well!!

                                                                              The Slab Bacon
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"No is not an answer and failure is not an option!"
Steve - WB3HUZ
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« Reply #6 on: October 28, 2007, 11:52:03 AM »

Many of the stations I regularly work on 80/75 meter AM are 200-500 miles out. I use a dipole that seems to work well. As others have stated, I'd stick with the dipole. I've never heard a local (someone within 300/400 miles) that wasn't PW when using a vertical on 75 meter AM.
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w5omr
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« Reply #7 on: November 01, 2007, 11:51:43 AM »

Many of the stations I regularly work on 80/75 meter AM are 200-500 miles out. I use a dipole that seems to work well. As others have stated, I'd stick with the dipole. I've never heard a local (someone within 300/400 miles) that wasn't PW when using a vertical on 75 meter AM.

It someone has room enough for an inverted vee on 75m, then they've got room for a delta loop (just close up the bottom of the vee, with more wire).  More wire in the air + open-wire feed-line = better signal (xmit & rx)

Here's mine.



Since that photo was taken, the feed-point has been moved and is now at the apex (~55'), not that I could really tell much difference.

My lot is merely 60' wide, and 120' deep. 

It can be done.

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WA1GFZ
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« Reply #8 on: November 01, 2007, 12:03:37 PM »

Cebik put a bunch of 2 meter antennas in this issue of QEX. One looked interesting for my Beach QTH because my lot is 175 by 60 feet.
I thought I could do the same thing scaled to 160M.
He bent the ends of a dipole around to form a triangle. I could do the same thing by making a 60 foot dipole across the top of the lot then bend the ends down the hill to get the full length in the yard to a tree an the bottom of the lot. I sent him an email and asked what he thought. He responded that the input Z would be low so try to have the ends as far apart as possible to bring the Z up.  I have never had much luck with loops close to the ground. They kick butt up in the air though. gfz
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w5omr
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« Reply #9 on: November 01, 2007, 01:23:36 PM »

Cebik put a bunch of 2 meter antennas in this issue of QEX. One looked interesting for my Beach QTH because my lot is 175 by 60 feet.
I thought I could do the same thing scaled to 160M.

Loop it.
1005 / 1.985 = 506' 4". 

a 60' Support pole, planted on the side of the property, around the middle of the property, to hold up the apex, then stretch the wire out to the ends of the property, support 'em with 40' poles and pull the wire out to the opposite side of the yard. 

Or, 40' poles in 4 corners, feed the square loop in the middle... that's what, ~170 + 170 = 340'? Add another ~50 and 50 for the opposite side makes another 100' for 440'... merely around 50~60' shy, but 100' of open wire line will cure that problem.  AND, it'll work -just fine- for 80m and up..

Quote
  I have never had much luck with loops close to the ground. They kick butt up in the air though. gfz

AD5HR has had a square loop up on 80m, fed in the middle of one side, and has DXCC on CW on 10, 15, 20, 40, is 8 shy of 80m and has worked multiple countries on 160m(*), with one antenna.

(* = he connected both sides of the 450Ω windowed ladder line to one side of his tuner, grounded the other and loaded up on 160m)

The antenna is 30' up, on 4 corners.
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WA1GFZ
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« Reply #10 on: November 01, 2007, 02:07:59 PM »

I only have one tree at the lower end of the lot. Horizontal loop does work though. I have about 120 feet between trees so can't get a 170 foot run. My # 8 feedline is pretty heavy so needs a support close by or I get a big sag. May have to change over to #10. I want a balanced antenna because the neighbors are close. It also leaves room for a center fed inverted l in the center of the lot where there is a 70 foot hickory tree. 
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w5omr
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« Reply #11 on: November 01, 2007, 03:58:09 PM »

I only have one tree at the lower end of the lot. Horizontal loop does work though. I have about 120 feet between trees so can't get a 170 foot run. My # 8 feedline is pretty heavy so needs a support close by or I get a big sag. May have to change over to #10. I want a balanced antenna because the neighbors are close. It also leaves room for a center fed inverted l in the center of the lot where there is a 70 foot hickory tree. 

Ever seen this done?


Qty: (3) 20' 2x4's. per support.  Measure, Drill, use some naval primer and battleship gray paint for weather proofing.

Install -one- bolt, swing the top arm (pre-fit with pulley and rope) to haul up aforementioned antenna, then use the second bolt to 'pin' the swivel part in place, then simply slap a flat-washer, lock-washer and nut on the back side, prime it and paint it.  Repeat for each support.

There's more'n one way to skin that cat! :-)
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WA1GFZ
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« Reply #12 on: November 01, 2007, 05:17:53 PM »

that would look nice in the front yard next to the 26KV primary "ready kw lead"
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w5omr
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« Reply #13 on: November 01, 2007, 10:17:50 PM »

that would look nice in the front yard next to the 26KV primary "ready kw lead"

It's made of wood, and the strain will be -away- from the high-voltage lines, were something to happen to it.

Don't know about up there, but we have a 10' conveyance on the property.  City Code compliance dropped us a 'nasty-gram' when I had a 30' pole stuck in the ground, 5' away from the curb.  It was 5' too close to the street, and 5' too close to the neighbors property line.
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ab3al
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« Reply #14 on: November 02, 2007, 11:13:19 PM »

on an inverted L now 

remember guys my house is a row house  actual back yard is 20x89  20 wide  89 deep  100 deep from the peak of the roof


The l is 1/4 on 160 no radials yet.. works fair on 80..

experiments start soon with no radial gound mounted off center loaded vertical dipoles  whew thats a mouth full
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