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Author Topic: Radials  (Read 1550 times)
KF7ITG
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Posts: 82




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« on: November 04, 2012, 09:45:26 PM »

I am considering installing a vertical antenna in the 40 to 70 foot range??? I live in Tucson where soil conditions are poor at best. So a decent radial field is a must. First a little background to work with. My property is about 200 X 200. The optimum place for a vertical for aesthetic reasons would be 22 feet east of my single story home. Also that would place the antenna just N and outside of the parameter (25 feet from the trunk) of a 75 foot conifer. That's two large objects with in 25 feet. My radial field would be asymmetrical.
Starting at 330 degrees to 20 degrees I have 110 feet available. From 20 to 30 I have 80 feet from 30 to 140 I have 60 feet from 140 to 180 I have 50 feet from 180 to 200 I have 85 feet from 200 to 330 I have 25 feet. These measurements for each section is the shortest radial length for that section. Some will be longer by 20+ feet but none shorter. The reason I am considering a vertical now is that I was to lazy to dig several thousand feet of trenches just to throw wire in for radials. As a secondary project with trenches already open I'm not so opposed to the idea. I am installing an extensive drip irrigation system and would like to drop a wire in all trenches before backfilling them. If I were to use the irrigation trenches it would roughly resemble a spider web over the area described. The wire I have on hand is 2, 500 foot rolls of 14 gage insulated copper wire and 6, 500 foot rolls of 20 gage insulated copper wire. I would prefer to use the 20 gage if it is heavy enough and use the 14 gage for an NVIS antenna. I have the 4.0 EZNIC software but I'm not proficient with it yet .... so....

73
James, KF7ITG
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AC5UP
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Posts: 3870




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« Reply #1 on: November 05, 2012, 04:17:18 AM »

...That's two large objects with in 25 feet. My radial field would be asymmetrical.

The only folks with textbook perfect verticals are typically AM radio stations or Norwegian Bachelor Farmers on the barren plains of Minnesota. The rest of us compromise with the resources we have. 20ga wire is good enough for radials and the insulation doesn't matter, but might be somewhat fragile mechanically. Do the best you can, and remember that on a good day when the propagation is working in your favor the antenna will work like you did everything right..... And on a bad day the guys with the big towers and beams are listening to static. Same as you.

( Except the big antenna guys can hear static from farther away than you can..... )  Wink
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WX7G
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Posts: 6049




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« Reply #2 on: November 05, 2012, 06:42:50 AM »

Your plan sounds good and even better than another Arizonian tower vertical user, N7IR. He is the big QRP signal on 160 meters from the West so we know that this works well.
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KB4QAA
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Posts: 2372




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« Reply #3 on: November 05, 2012, 12:08:37 PM »

I'm sorry I can't make it thru the original post.

-Any radials are better than no radials.
-Do what you can.


Here are some oft repeated tidbits about radials:
Quote
Here is Rudy Severns' N6LF research condensed into a powerpoint show.
http://www.antennasbyn6lf.com/files/ground_system_tests.pps

N6LF has done extensive practical research which answers many questions that were debated for years before computer modeling came along  Here is his main website.   This is a treasure trove of info.
http://www.antennasbyn6lf.com/design_of_radial_ground_systems/

OK, what the heck i'll answer the remainder of your questions:   Smiley
-Always follow the manufacturers instructions for mounting height and radial installation
-It isnt' helpful to have radials with much vertical component running to the feedpoint

-Radials should run directly away from the antenna in a straight line without crossing or interconnecting, these can cause hysteresis currents and all sorts of problems
-Ground radials can lay on ground, be pinned down (super idea), or be buried to a depth of a few inches.
-Radial wire can be bare, tinned or insulated.  It does not need to be staked or grounded the far end except in unusual circumstances.  Radials are not intended to couple with the soil.
-If you come to an obstacle, terminate/cut your radial
-Ground radials do not need to be a specific length because they are detuned by the soil
-A few missing or short radials will not cause a 'black hole' effect in that direction
-The purpose of radials is to return the E/M flux current to the antenna
-Copper is over 1000 times better conductor than earth, so even a small conductor is better than earth, this is also why you don't need to carpet your backyard with solid copper, and why some short or missing radials are not critical
-How long?  A half wavelength would be ideal.  A realistic trade off is around 0.2-0.25 wavelength (1/4 wavelength), which probably also happens to be the height of your antenna on the lowest wavelength! 
-How many?  (personal opinion)
4-may actually be worse than just a vertical and ground rod.  Makes contacts but poorly
8-Just enough to stabilize impedance; somewhat better
16-Probably the minimum you should have
32-Should have good performance
64-Quite good performance, but plenty of effort to install
120-Open your own broadcash station!  The FCC smiles upon you.  Engineers come to your station for ground reference measurements.  Smiley
-
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N6AJR
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Posts: 9908




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« Reply #4 on: November 05, 2012, 01:26:12 PM »

yup, a decent verticle and a good radial feed will do fine. use rope guys to hold up the vert, and I use a "hedge hog" which is an edger with a steel blade, to cut groves in the ground, sutff in a wire, and stepp on it to close.  putting in with the  irrigation will do also, drop 2 in each run.  as many as you can and as long as you can is good.  bending ends and  zig zaging them is ok , just don't cross radials over radials.  have fun
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K2OWK
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Posts: 1061




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« Reply #5 on: November 05, 2012, 02:34:18 PM »

I used a half moon edger (manual) to cut groves for my radials. It worked well but is a little labor intensive. I installed 20 radials most at 26 feet 9 inches.

73s

K2OWK
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K3VAT
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Posts: 709




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« Reply #6 on: November 05, 2012, 03:02:47 PM »

I am considering installing a vertical antenna in the 40 to 70 foot range??? I live in Tucson where soil conditions are poor at best. ... 73 James, KF7ITG

Question: is a mounting a horizontally polarized antenna, simple dipole or derivative, simply out of the question?  Any possibility of using that conifer tree or erecting one or two tall supports such as what can be done with the many types of deployable telescoping masts (they make them to 60', good enuf for 40M thru the upper bands)?

The reason I ask is that for a vertical, the far field ground condx play an important role in determining the strength and elevation angle of your signals.  So just having a 100' copper disc below your vertical isn't in itself a guarantee of good performance.

73, Rich, K3VAT
« Last Edit: November 05, 2012, 03:11:40 PM by K3VAT » Logged
KF7ITG
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Posts: 82




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« Reply #7 on: November 05, 2012, 07:15:34 PM »

I do have an 80 meter dipole at 40 feet. The other side of my property away from the conifer is a 60 foot palm tree. Actually in the east to west orientation I am able to hang 350 feet of wire. While I live in the city we live in an area that was never annexed by the city so technically I live in the county. I could erect a 100 foot tower if I wished, no zoning issues. I believe it's $100 for the permit, just submit the manufactures tower specs and the footer specs. There is only one inspection for per concrete. After that you are on your own. No tower inspection. So there are many options. I just thought a low profile vertical might be fun if it would work with the limited radial area.

73
James, KF7ITG
« Last Edit: November 05, 2012, 07:18:50 PM by KF7ITG » Logged
K3VAT
Member

Posts: 709




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« Reply #8 on: November 06, 2012, 06:51:22 AM »

I do have an 80 meter dipole at 40 feet. The other side of my property away from the conifer is a 60 foot palm tree. Actually in the east to west orientation I am able to hang 350 feet of wire. While I live in the city we live in an area that was never annexed by the city so technically I live in the county. I could erect a 100 foot tower if I wished, no zoning issues. I believe it's $100 for the permit, just submit the manufactures tower specs and the footer specs. There is only one inspection for per concrete. After that you are on your own. No tower inspection. So there are many options. I just thought a low profile vertical might be fun if it would work with the limited radial area. 73 James, KF7ITG

OK, James.  I didn't see what your operating goals were: DX'ing, lowband operation, rag chewing with the 'locals', etc.?  If you are content with working with what your hear with your current setup, and just want some improvement, then you could add a 40M/80M vertical like the Butternut HF2V OR even their 4 or 5 band model and with a couple dozen radials and that would seem to be an improvement over the 40' high 80M dipole.  If you want to get into DX'ing (or continue DX'ing if you're already bitten), then the tower with yagi(s) is really the only way to go.  You might want to search around this Forum and also on the Antenna & Towers Forum to get an idea of what might work for your operating goals and your budget.  GL, 73, Rich, K3VAT
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