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Author Topic: radial installation on vertical's  (Read 27316 times)
N2BIX
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Posts: 24




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« on: June 15, 2011, 07:36:30 PM »

I have always used  either dipoles or beams and now i would like to try a vertical out. I had purchased a MFJ 1798 80-2 vert but with all the reports i have read since about it's wind survivability i have decided it won't last where i am. I want to use a s9v 43' vertical now carried by LDG. My question to you vertical guy's is this. Does it matter if you use insulated wire for the radials or should you use bare wire? I intend to bury the radials a few inches below the soil. Also , should i try to cut the radials for each band i intend to use or should i just make them for the lowest freq used? If i can't put the radials in a 360 degree pattern will it make a big difference in the radiation pattern?How many radials ,at the minimum would you recommend for good results? Where i am on the jersey shore, if you go down 5 feet you hit the water table. Would some long ground rods into the soil help as well? Thanks I am looking forward to hearing what you have to say.ps i realize i need a tuner with the s9v. Wink
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WB6BYU
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Posts: 17039




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« Reply #1 on: June 15, 2011, 09:15:57 PM »

Dirt is lossy at RF.  You want the RF to flow through the wires, not the dirt.  The shallower you can
put the radials the higher the efficiency on HF.  The simplest approach is often to mow the lawn
short, secure the wires to the ground with some sort of staples, then let the grass grow over them -
they'll soon be lost in the thatch.

Radial wires can be bare or insulated, and don't have to be very thick.  If you have 20 radials, then
each would carry 1/20 of the total feedpoint current, so  #20 wire should easily handle a kW (except
perhaps on 160m) and will loaf at 100W.

Because the radial wires are detuned by the dirt, cutting them to standard formulas won't make a
difference.  (In fact, a quarter wavelength in air may be a half wavelength on the ground, which
isn't a particularly effective length.)  More radials are better, longer radials are better (up to a point),
and there is some optimum combination for a given length of available wire, but you can start with
something like 16 radials each 20' long and get pretty good results.

Ground rods don't help much for RF:  if the soil is very conductive then the skin depth is pretty
shallow, so only the upper part of the rod is useful.  If it isn't very conductive, then the ground
rod won't make very good contact.  (They are useful for lightening or AC power protection, but
not particularly for RF.)

Most people have some sort of obstructions in their radial field - just do the best you can.  There might
be some minor changes in the pattern if the radials are bunched only in certain directions, but not enough
to worry about.



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W0BTU
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Posts: 2217


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« Reply #2 on: June 15, 2011, 09:45:48 PM »

...  The shallower you can put the radials the higher the efficiency on HF.  The simplest approach is often to mow the lawn short, secure the wires to the ground with some sort of staples, then let the grass grow over them ... Radial wires can be bare or insulated ... More radials are better ... Ground rods don't help much for RF...  only the upper part of the rod is useful. 

This is GREAT advice!   Smiley

I'd like to either quote it or link to this post from my web page concerning the importance of ground radials.
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AD6KA
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Posts: 2243




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« Reply #3 on: June 15, 2011, 10:06:05 PM »

Quote
i realize i need a tuner with the s9v
And the best place to put that tuner is at the base of
that 43' vertical, especially if you have a long coax run.
Look into remote auto tuners. Some hams have remoted
regular auto tuners in a waterproof enclosure. You can
easily run the DC up the coax with a simple insertion and
retrieval circuit. MFJ even makes an off the shelf version.

Consider a 1:1 UNUN and low loss coax if you are using
a shack tuner.

You know, the 5BTV and 6BTV are very good performers
and quite economically priced.
Especially compared so the
S9 43' Vertical, which is a little pricey for what you get.
LDG raised the price over what S9 charged, too, didn't they?
And the need for a tuner would be not so critical.
It's something to consider anyway.

Good luck with your antenna project.
73, Ken  AD6KA
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K5USF
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Posts: 83




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« Reply #4 on: June 16, 2011, 10:32:33 AM »

Hello,

I have the 31' and the 43' S9 Vertical.  I have 32 radials ranging from 10 feet to 120 feet in length.  Though most of the radials are 30-50 feet long.  My tuner is a MFJ-998 AT mounted in a NEMA box at the base of the antenna.  I use the bias T and run the power down the coax to the tuner.  There are a few pics on QRZ.  It gets windy here in the desert, so I like the option of swapping out the S9 antennas. I plan to get the 18 footer for those real windy days.  Also, I have a couple of home brew base coils so I can operate 160m (not that much) or 80m.  Although, I can tune the 43 footer on 80m without the base coil, I added one anyway to get the SWR down.  Jim
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W5WSS
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Posts: 2271




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« Reply #5 on: June 16, 2011, 04:23:28 PM »

N2bix, buried radials deteriorate rather quickly so I would suggest reading the dx engineering technical about why theirs lasts much longer than other insulated brands. 73
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KD8IWZ
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Posts: 56




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« Reply #6 on: June 16, 2011, 04:51:56 PM »

I have found the S9V31 at the dealer I frequent for $84.95, makes it a lot more affordable. (Wish they would have had it at Dayton)

73    Dale
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W0BTU
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« Reply #7 on: June 17, 2011, 01:38:02 AM »

buried radials deteriorate rather quickly...

Then don't bury them. :-)

From WB6BYU's post above:

"The shallower you can put the radials the higher the efficiency on HF.  The simplest approach is often to mow the lawn short, secure the wires to the ground with some sort of staples, then let the grass grow over them - they'll soon be lost in the thatch."

This is THE way radials should be installed.
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N4CR
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Posts: 1757




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« Reply #8 on: June 17, 2011, 03:02:57 PM »

...  The shallower you can put the radials the higher the efficiency on HF.  The simplest approach is often to mow the lawn short, secure the wires to the ground with some sort of staples, then let the grass grow over them ... Radial wires can be bare or insulated ... More radials are better ... Ground rods don't help much for RF...  only the upper part of the rod is useful. 

This is GREAT advice!   Smiley

I'd like to either quote it or link to this post from my web page concerning the importance of ground radials.

Link this: http://home.comcast.net/~k6mhe/GroundSystems.pdf

This guy did his homework.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
KB4QAA
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Posts: 3255




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« Reply #9 on: June 17, 2011, 05:37:19 PM »

N2bix, buried radials deteriorate rather quickly so I would suggest reading the dx engineering technical about why theirs lasts much longer than other insulated brands. 73
That is not universally true.  It is highly dependent on soil conditions.   Most hams have no problems with radials deteriorating for the length of time they use them.   I if it were a problem why do commercial radio station use them?  Certainly they want long life and economy.

Ben Franklin installed the lightning rod system on the Maryland State Capitol.  They finally renovated it about 5 years ago and pulled up his intact copper ground wire from the ground.  I'd say 230+ years is pretty good service life!    Wink
« Last Edit: June 17, 2011, 05:40:07 PM by KB4QAA » Logged
AA5WG
Member

Posts: 511




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« Reply #10 on: June 18, 2011, 03:50:56 PM »

Hi N2BIX:
Here is a link for you to check.  Elevated radials seem to have the edge.  
Good luck.
Chuck
http://amfone.net/Amforum/index.php?topic=27964.0Chuck
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N4JTE
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Posts: 1169




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« Reply #11 on: June 18, 2011, 10:24:46 PM »

Before you do anything check out N6LF website.
regards,
Bob
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W0BTU
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Posts: 2217


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« Reply #12 on: June 19, 2011, 01:41:30 AM »

Link this: http://home.comcast.net/~k6mhe/GroundSystems.pdf This guy did his homework.

Yes, that's a well-established study that was done many years ago. I linked to it at
http://www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html
Thank you.

And ditto on N6LF's work! I have a link to it from that page, also.
« Last Edit: June 19, 2011, 01:43:50 AM by W0BTU » Logged

W8JI
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Posts: 9749


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« Reply #13 on: June 20, 2011, 05:23:19 AM »

N2bix, buried radials deteriorate rather quickly so I would suggest reading the dx engineering technical about why theirs lasts much longer than other insulated brands. 73

Gosh, I have bare buried radials installed in 1998 and they look like new.

Back in Ohio, a person who bought one of my old houses tells me they still cuss as intact pieces of copper I installed in 1970 are pulled out of the garden.

At broadcast stations, radials installed in the 1920's are still as good as new, some systems almost 100 years old.

I don't agree with the idea a buried copper radial of adequate size deteriorates, unless it gets plowed through.

I do not think a 43 foot vertical would be my first choice. I would use a good trap vertical, like a 6BTV.

73 Tom
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N4NYY
Member

Posts: 4941




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« Reply #14 on: June 20, 2011, 08:06:45 AM »

I am going to try the reverse, going from a 5BTV to a G5RV, sometime in the fall.

I did it backasswards. I got my ticket in 2005, at least 4-5 months before I got a rig/antenna. Note, that I was out of any kind of radios and antenna theory for over 22 years. So I had to start from scratch.

I made the unfortunate installation of a 5BTV before I found eham. So I used the Hustler instructions to install the antenna. I ground mounted it in a wet swamp. I only put up a few radials. Then I found this place, and numerous engineers suggested the DX Engineering instructions, and various articles on ground fields. Bottom line, I have to add numerous radials (unburied). Now, the swamp must have helped as it works well on 80-40-20 (I mean works well making contacts), but still, it appears I screwed it up and might not be all that efficient.

So, I am going to try my hand at a dipole, specifically the G5RV in an inverted V. I don't think it can be any worse.

Regarding burial of radials, it appears to be a lot of work. Numerous people suggested that you just work the radials into the grass, and then let the grass grow over. DX Engineering recommends it. If you truly want to bury your radial, the easy route might be to lay them out on the ground, drop 1 inch of top soil on the radials, and then grass seed the soil. otherwise, If you are going to bury 20-40 radials, it will be alot of work.

BTW, the main reason I am going to try the G5RV, is that the wet swamp has enormous growth of vegetation, that requires me to cut it down twice per year. In addition, it is a filthy area full of pests, like ticks and so forth. After 6 years, I am pretty fed up with that.

  
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