Shon,
The radials can be installed on the ground to several inches under the
ground. I would run 30 or more radials 50' or longer. That is three 500'
rolls of THHN wire. In the directions where you don't have this length don't
bother to bend the longer radials, simply install shorter radials. Yes #14
or #12 standed THHN house wire is great. Easy to work with and it will last
forever being copper. One or two 8' ground rods at the antenna base will
provide a measure of lightning protection. The radials also help with this.
Don't worry too much about the ground system. The difference between a dozen
25' radials and sixty 50' radials will be roughly 3 dB.
If you are interested - and it would be good data to distribute - you can
measure the ground resistance as you install radials. Install 4 radials.
Measure the antenna input impedance at resonance on 80 meters. Now 8
radials. 16 radials. And so on the radiation resistance of the 53' vertical
on 3.5 MHz is 20 ohms. Measure the resistive part of the input impedance and
subtract 20 ohms. That is the effective ground loss resistance at 3.5 MHz. I
do this when I install verticals and it gives a good feel for how little is
gained for much effort in radials. Where the extra 1 or 2 dB matter is on
weak signal low band DXing where signals are at or below the noise level.
This is the kind of DXing I do every day. I need that extra 1 dB.
An MFJ-259 antenna analyzer or similar can be used for measurements. You
might check that the measurements remain the same before and after sunset.
If they change after sunset it means a local AM BC station is overloading
the MFJ-259 during the day. At night AM BC stations drop their power.
I have never used a balun with a ground mounted vertical. I don't think you
will need one. I can examine the hytower assembly manual to see how to add
30 and 60 meters. Or, make do with a tuner in the shack.
Check the loss of RG-213 and LMR-400 coax for the length you will run and
decide from that. For best lightning protection run the coax to the house AC
service entrance and bond the coax shield there. Then run the coax to the
shack. This eliminates a lightning current path through the house wiring.
I think the Hytower connects the coaxial cable shield to the GND.
This is the antenna I plan to use when I move to a non-CC&R neighborhood. Be
aware that this antenna will not run 1 kW on 160 meters without modification
of the base insulators.
Dave WX7G
On Thu, Mar 4, 2010 at 12:19 PM, Shon Edwards <sre.1966@gmail.com> wrote:
> Hello all, I'm getting a Hy-Gain AV-18HT and have several questions about
> it, especially about a radial system. I am very new to HF and so am quite
> clueless, but would be grateful for any help possible.
>
> How deep do the radials need to be underground? Is 2 or 3" OK?
>
> I wonder if it's necessary (as some say) to put down radials only at a
> percentage of the wavelength of the lowest frequency you plan on working
> on,
> or (as others say), do you need to put down radials at a percentage of the
> wavelength of all frequencies you plan working on? How many radials should
> be put down for each band, if it is necessary to go this route?
>
> Also, how long should these be? I have lately read Rudy Severn's article in
> QST this last month, which was excellent, but it doesn't always answer all
> my questions. Also, his 7 articles on the Internet he refers to don't
> readily answer all these questions, although very good articles, all of
> them. Is it .4 wavelength if I plan on doing 60 radials or .25? .2?
>
> I'm also wondering if I have a space problem, if I must absolutely, put out
> my radials in a straight line, or if I can bend them, and go around things
> in my yard at angles of around 70 degrees, if need be. Will that have a
> negative effect on my radiation pattern? I have about a 90 degree section
> of my antenna radial field, where I will need to be bending lots of radials
> up to 70 degrees. Unfortunately, this is the exact direction that I want
> to
> focus on most for most of my communications, toward the east and northeast,
> southeast.
>
> What is the best type of coax to use if I want to minimize losses the most
> at 1-30 MHz? It doesn't matter if it is expensive. I'd just like to get
> as
> many dB of gain as possible.
>
> Also wondering how best to ground the antenna. This might be for a person
> who is familiar with this particular antenna. Apparently, an SO-239 is
> provided and connected to the antenna already. I understand that the braid
> of the coax needs to be soldered to the ground rods and that they should
> all
> be connected together, but if I am connecting a PL-259 to an SO-239 on the
> antenna, how would I do this? Solder some part of the SO-239 to the
> ground?
>
>
> Also, if I want to add 30 M and 60 M capability to this antenna, which is
> 53' high (so it should be possible, I would think), how do I do it? I
> probably wil not be too good here with the technical terminology, but I'll
> do my best.
>
> Does the size/type of the wire of the radials matter? I've heard that it
> does not, but I imagine that stranded wire, though more pliable and easy to
> deal with, would deteriorate faster than solid wire. Also, am thinking of
> using #14 wire. It seems to be the best I can get for the price at Home
> Depot. I've heard of people using chicken wire, but I want something more
> permanent than this. Also, I'm thinking if I use plastic-clad wire it will
> last longer than bare wire. That is, it would not rust or fall apart over
> the years as fast as wire that is bare.
>
> Also, any other things that I might need? Like a balun or anything else
> that I'm not thinking of.
>
> Thank you and sorry I have so many questions. As I say, I'm just getting
> into this. Thanks, Shon Edwards, sre.1966@gmail.com.
>
> --
> Shon R. Edwards,
> Radio:
> Amateur Call: KO3U
> Commercial radio licenses:
> GROL: PG00016801
> GMDSS/O/M: DB00000391
> GMRS: WQKW341
> 2nd class radiotelephone: T2GB064388
> Accredited VE: W5YI, ARRL
> ARRL Instructor
> 1039 N 2575 W
> Layton, UT, 84041-7709
> USA
> e-mail: sre.1966@gmail.com
> phone: (801) 444-3445
> cell: (801) 336-7635
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