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Radial Wire Installation

R

rfry

Here is my response to statements on this subject made on another board...

>Radials must be bare copper wire
>buried at least a few inches underground.

Quoting Edmund Laport's Radio Antenna Engineering (McGraw-Hill 1952) about installing radials for MW antennas:

"The depth of the wires is immaterial, whether the soil be moist or dry. They may be placed on the surface except that they are then subject to injury and prevent the use of the land for other purposes."

When the radials are not buried, it doesn't matter whether or not they are bare. The currents they carry are r-f currents, which enter the wires by radiation. The earth itself is a rather good insulator, and bare wires buried in the earth are therefore surrounded by "insulation," also.

>The longer the radials are, the better
>ground contact you will get.

The improvement in the performance of the ground system with added radial number/length comes not from "better ground contact," but from the fact that they then intercept more of the r-f current induced into the earth by the vertical radiator-- most of which is contained in a circular area around the radiator having a radius of about 1/2 wavelength.

If better ground contact was the only issue, that could be achieved by burying short coils, zig-zags, or loops of wire of the same total length, or copper plates having the same surface area as the normal radial system layout. But it wouldn't work well, because the r-f currents then have to travel through 1/2-wavelength or so of earth to reach those conductors, and in doing so they have encountered high r-f losses before they ever reach the buried ground conductors. Those losses are in series with the antenna current, and so the radiation efficiency of the antenna system is reduced.

//
 
> How thick should the wire be?
> Also what do you think about length and amount of radials?
___________

For these power levels the wire gauge can be quite small. Probably 18AWG is big enough for Part 15 AM.

The fewer radials you install, the shorter they might as well be, because their effective length depends on their number. An example:

For a radiator height of 0.1 wavelength, the r-f currents flowing in a system of eight ground radials falls to about 5% of its maximum value for radials that are about 0.13 wavelengths long. If 32 radials are used, current doesn't fall to 5% until radials reach 0.47 wavelengths.

This doesn't mean that 8 radials are as good as 32 -- it means that extending a few radials for long distances doesn't do much good. The r-f currents reaching them have to travel through a lot of lossy earth to get there, so antenna system efficiency is reduced.

//
 
If you could, please put it in terms I understand.
If i have a signal on 1610am, how long should my radials be?
How many do you suggest

thanks
simcha
 
> If you could, please put it in terms I understand.
> If i have a signal on 1610am, how long should my radials be?

Many short radials are better than a few long ones. The radials need not be much longer than the antenna is tall, since the near field of a short vertical antenna is much more compact.

10 or 20 bare copper radials 3 m - 4 m long and made of solid copper wire #18 gauge or larger are fine for your frequency. Information Station Specialists use radials of this size for TIS (Travellers Information Stations) on the high end of the AM band. Paving the whole back yard with copper sheet will work better, but the amount of performance gain isn't worth the effort. -- JasonW
 
When you speak of antenna height are you referring to the actual antenna or how high i mounted it? My antennas are about 12 to 25 feet high.

Also when you say 18# or larger is that mean 18 or thinner or thicker like in 12 gauge?

Also I read some guy writing that he has an interesting irrigation drip system over each of is grounds that seems to help is signal, that sounds good because my listeners always tell me the signal is great in the rain.
 
> When you speak of antenna height are you referring to the
> actual antenna or how high i mounted it? My antennas are
> about 12 to 25 feet high.
>
> Also when you say 18# or larger is that mean 18 or thinner
> or thicker like in 12 gauge?
>
> Also I read some guy writing that he has an interesting
> irrigation drip system over each of is grounds that seems to
> help is signal, that sounds good because my listeners always
> tell me the signal is great in the rain.
>


Simcha... try using 12 guage insulated wire from HomeDepot, it's $26.00 for a 500 foot roll and for radial systems this works great, also when you install the radials in the ground.. surround each 'bare' wire with clay cat litter, this binds the wire and gives it the equivalent of a larger diameter rod as the clay compacts itself. This is why ground rods work so well... as it's driven into the earth it compacts the clays around the copper rod, thereby increasing it's electrical capabilities.

Rock salt used for water softeners also work well sprinkled on the soil and
watered down using the sprinkler system or some other method, increasing it's conductance.

Radiopilot
 
> When you speak of antenna height are you referring to the
> actual antenna or how high i mounted it? My antennas are
> about 12 to 25 feet high.

I'm referring to the distance from the ground up to the tip of the antenna (I assumed the antenna sitting on the ground to make the description simpler).

> Also when you say 18# or larger is that mean 18 or thinner
> or thicker like in 12 gauge?

#18 to #12 gauge--larger diameter than #12 is a hassle to solder and won't noticeably improve the performance. I'd use an 8 foot ground rod as the center tie-point for the radials, as the rod will give you a good DC Earth ground to bleed off static charges.

> Also I read some guy writing that he has an interesting
> irrigation drip system over each of is grounds that seems to
> help is signal, that sounds good because my listeners always
> tell me the signal is great in the rain.

One Australian crystal radio DXer used to tie his security dogs to the ground rod, and what they did to mark it *did* improve his reception. A late ham radio friend of mine (he was also a local Miami talk radio host) told me that if he ever built an AM radio station, he would set up windmills to pump water and flood the radial field. Yes, wet soil is your ally. -- JasonW
 
Simcha... try using 12 guage insulated wire from HomeDepot,
> it's $26.00 for a 500 foot roll and for radial systems this
> works great, also when you install the radials in the
> ground..

When you say insulated wire where is bare that i can surround it with kittylitter ?

thanks
 
Thanks the only thing is that the radials are going to be quite long. Rangemasters antenna tips are probably 20 to 40 feet off the ground each.
By the way one cant use the same ground and radial system for two rangemasters or can they?

The dog story is very funny, maybe that is another reason why the kitty litter works to, I have plenty of stray cats in my area.
 
> Simcha... try using 12 guage insulated wire from HomeDepot,
> > it's $26.00 for a 500 foot roll and for radial systems
> this
> > works great, also when you install the radials in the
> > ground..
>
> When you say insulated wire where is bare that i can
> surround it with kittylitter ?
>
> thanks
>


The wire must be stripped, I mentioned the insulated wire is because it's the cheapest way to buy for that gauge, bare copper wire is usually sold by the foot and it cost more.

This is what I used on my 64 radial system, this Christmas holidays, I will install the other 64 radails and try to improve my system.. it's very good now, but like Rfry said the RF at the antenna must 'find' the radials for it to be effective...

Radiopilot
 
Unless the soil is sand or some other very poor conductor, bare copper wire is preferable to insulated wire for radials.

The antenna ground current return losses in the soil around and under the antenna occur because the soil is like a bunch of resistors in series. The radials function to "short out" these resistors and create a low-resistance ground return path. If they're insulated, they can't do that. However, if the radials are lying on or in sand or volcanic soil, the soil conductivity is so low that it won't make much of a difference whether they're insulated or not. -- JasonW

> > When you speak of antenna height are you referring to the
> > actual antenna or how high i mounted it? My antennas are
> > about 12 to 25 feet high.
> >
> > Also when you say 18# or larger is that mean 18 or thinner
>
> > or thicker like in 12 gauge?
> >
> > Also I read some guy writing that he has an interesting
> > irrigation drip system over each of is grounds that seems
> to
> > help is signal, that sounds good because my listeners
> always
> > tell me the signal is great in the rain.
> >
>
>
> Simcha... try using 12 guage insulated wire from HomeDepot,
> it's $26.00 for a 500 foot roll and for radial systems this
> works great, also when you install the radials in the
> ground.. surround each 'bare' wire with clay cat litter,
> this binds the wire and gives it the equivalent of a larger
> diameter rod as the clay compacts itself. This is why ground
> rods work so well... as it's driven into the earth it
> compacts the clays around the copper rod, thereby increasing
> it's electrical capabilities.
>
> Rock salt used for water softeners also work well sprinkled
> on the soil and
> watered down using the sprinkler system or some other
> method, increasing it's conductance.
>
> Radiopilot
>
 
> Thanks the only thing is that the radials are going to be
> quite long. Rangemasters antenna tips are probably 20 to 40
> feet off the ground each.
> By the way one cant use the same ground and radial system
> for two rangemasters or can they?

I'd ask Keith Hamilton. If both RangeMasters are on the same frequency I wouldn't think it would be a problem, but if their frequencies are different it might matter.

> The dog story is very funny, maybe that is another reason
> why the kitty litter works to, I have plenty of stray cats
> in my area.

Urine is a great electrolyte. If you could borrow my neighbor's draft horse (who makes rivers of the stuff), you'd have it made! :) -- JasonW
 
yes it is two different channels.


> Urine is a great electrolyte. If you could borrow my
> neighbor's draft horse (who makes rivers of the stuff),
> you'd have it made! :) -- JasonW
>
We could put the stuff in jars and sell it on ebay

"Mr Ed's Broadcast Tonic"


Note - Do not drink.
 
Hi Guys,

Last I looked in our local Home Depot they had 100ft and 500ft spools of bare copper wire in various heavier gauges (14, 12, 10). The bare-wire spools were cheaper than the insulated wire spools. Electricians use the spooled wire to pull thru plastic conduit. The bare copper wire is for ground and the white and black wires are for neutral and hot. If your local Home Depot (Lowes, or whatever) doesn't stock spools of bare copper wire, go to any local electrical supply store. They will have it and it will be cheaper than insulated wire. Stripping long lengths of insulated wire is a daunting task!


<P ID="signature">______________
Phil B
</P>
 
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