Well, not so quick.
High end academic research on radials and related ground interactions
effectively ceased in the 1940's when commercial broadcasting got their
solution in FCC standards for commercial MF AM broadcasting antennas. It
ceased when the money for research predictably dried up. The research
buck had reached the point of severe diminishing returns on improving radio
station power bills. Attention went elsewhere.
Further, researchers had exhausted their tool's capabilities, and I could
see where they could have gotten to with the tools of their time, because I
used most of them going to work for AT&T as a 20 year old in 1963.
One subject never explored was comparisons of less than optimum radial
density for SKY wave, because the cost of 120 5/8 wave buried #4 copper
radials was only a drop in the bucket of the capital expenditure for a
working AM station, and AM bread and butter was ground wave, not sky wave.
There is nothing out there about getting the most out of necessarily
suboptimal situations in which we hams find ourselves, where our land
purchases do not include the acreage for commercial BC antenna solutions.
Tools capable of an extension of this science, AND affordable by average joe
ham, did not appear until the 21st century, effectively really the last 5
years, give or take.
Far more expensive tools have been around for 25 years, BUT there was NO
MONEY for the research, since the commercial AM was all settled in the
1940s, and nothing to be gained by spending money. AND you can see why,
given what measurements we are discovering now.
MEASUREMENTS of the effective feed resistance of wire in/on
dirt/sand/swamp/seawater/manmade materials, will give you effective series
resistance PER RADIAL of anywhere from half an ohm to 150 ohms. The latter
is found over sand and some backyard dirt, and over paving materials. The
chemical explanation of that is beyond our budget and need. Just that the
condition exists and is nearly impossible to predict, and requires
MEASUREMENT to know, should give anyone pause about blanket statements about
someone else's UNmeasured situation, and using the results of an experiment
run in only one place. MEASURE, THEN DECIDE.
We found places where the resistance varied between 40 and 95 ohms depending
on where the wire was placed on the SAME piece of property. Sea water and
salt water marsh was predictable. Nothing else. Well, maybe sand a lot of
the time, but that too is inexplicably variable. Plenty of SWAG on that and
some of it probably right, too, but unproven.
But let's take the nasty 150 ohms worst case. A very ugly 150 ohms divided
by 120 is 1.25 ohms effective series resistance as the current sink for the
non-radiator connected half of the feedline. For an antenna that is 32 ohms
resistive feed at the base, the power loss is 20*(log(32/33.25)) or merely
one third of a dB. Quite respectable, particularly given that the 150 is
the evil worst case. So 120 #4 blows away the problem with certainty. 120
evenly spaced good radials leaves one with no possible improvements in the
power bill by piddling with the radials.
The radials are #4 for survivability. Lightning currents evaporate even
heavily paralleled #18, while #4 sticks around. #18 corrodes through a lot
quicker than #4. Raised #18, where you can see it, is one thing. BURIED
#18 is another. It may or may not work long term for an individual
situation. That depends on the dirt. If #18 was commercially feasible, they
would have used it. There are very pragmatic reasons for the commercial
standard.
Measuring locally, velocity factor came out between 40% and 80% for
insulated wire buried or laying on ground, again with large variability in
the same back yard or area. The suspicion, impossible to prove, is water
table, septic fields, and variation and layering of natural soils type
deposits (like sand and clay in mine), or fill dirt brought in to level out
property prior to building construction.
What we hams have done is to extrapolate this VERY NARROWLY construed
commercial standard into significantly deficient situations from whatever
unavoidable local restrictions, property, budget, whatever. It turns out
that there clearly are fall-off-the-cliff points where this extrapolation
goes invalid, which start when you abandon "dense" radials.
My antenna for the 2011 CQ 160 CW contest, at 100 watts, netted me claimed
927 contacts, 38 countries and 58 states/provinces. The antenna had **NO**
radials. Comparisons with another station in the Raleigh area using the
comparative analysis tools of the Remote Beacon Network were compelling. He
was also running 100 watts using 20-some miscellaneous radials on the ground
in his miscellaneously shaped back yard. His 160 setup was very typical of
many reported on this reflector and sometimes praised for "how well" they
work. In the RBN graphs, my friend was consistently down ten dB in any
direction, and sometimes worse than 10 dB.
Read that again... A non-typical 160 vertical antenna with **NO** radials
was consistently 10 dB or more better than a commonly reported ham
radials-on-the-ground solution.
What in your understanding of how these things actually work explains that?
The common "wisdom" says you cut back on the radials to "fit" either the
budget, construction time available, and you lose a few dB from the
commercial standard.
NEC4, with all the issues regarding the effect of dirt, given any ground
construct, duns my 160 antenna 2 db from the commercial standard. That in
turn estimates my friend's antenna at 12 dB down from the commercial
standard in the model, given his MEASURED 10 dB down from mine. 12 dB is a
pretty severe penalty for going to miscellaneous radials. That's like
turning off the big amp.
The common understanding of miscellaneous radials "estimates" a few dB down
from a commercial standard, but is in fact saddled by 10 dB MORE than
whatever my no-radial antenna is in fact down from a commercial standard.
As to concrete, high level academic grade research into these measured
contradictions, there isn't any, and the contest results exceed my knowledge
about exactly how they work, and leave the typical extrapolated radial
nonsense in the dust. I was quite surprised by my success. You can't explain
the score by superior operating, as I can give you a list of some dozens of
contest operators, usually at the top of results, who leave me in their
dust, contest after contest, year after year.
Number 5 USA low power in a major contest is not where you find me single
op. My big numbers over my lifetime are as a team member multiop. And 100
watts is 100 watts.
It ain't the operator, ain't the power, requires receiving well which IS
true here, which leaves only the antenna as major diff. To be truthful,
beyond the AM BC commercial standard, we really understand dink about 160
antennas in less than optimal situations, and we mostly are trapped in a
seventy-year-old invalid extrapolation of experience with mandated
commercial AM BC radial overkill.
We need to fess up we really DON'T know how and why it works, other than
with dense radials, and get on with finding out how it DOES. We have really
neat tools these days, that those gents back in the 40's would have killed
to get their hands on.
Do tell somebody to do dense radials, because that DOES really work. But
beyond dense, we start working without reliable predictors. Beyond dense,
things start to fall off the cliff.
73, Guy.
On Thu, Aug 18, 2011 at 9:16 PM, Gary K9GS <garyk9gs@wi.rr.com> wrote:
> Hello Jorge,
>
> There is very little current flowing in each radial wire so the wire
> size matters very little. In your example you would be much better off
> with the 120 radials than 40. Keep in mind though that 120 radials is
> way too many and a waste of wire.
>
> For a great discussion on radials see:
>
> http://www.antennasbyn6lf.com/design_of_radial_ground_systems/
>
> There are a lot of other great articles on this site as well.
>
> See you on the air..........
>
> On 8/18/2011 8:13 AM, Jorge Diez - CX6VM wrote:
> > Thanks all for the answers...
> >
> > I am working on collection the materials for the project, so all feedback
> is
> > very important for me, thanks.
> >
> > Just was thinking, is the same or better to have 120 radials of AWG18
> than
> > 40 radials of AWG8? What´s the idea? This is the same amount of copper,
> but
> > the distribution over the ground is different.
> >
> > 73,
> > Jorge
> > CX6VM/CW5W
> >
> >
> >
> > -----Mensaje original-----
> > De: topband-bounces@contesting.com [mailto:
> topband-bounces@contesting.com]
> > En nombre de Jon Zaimes AA1K
> > Enviado el: Miércoles, 17 de Agosto de 2011 05:42 a.m.
> > Para: topband@contesting.com
> > Asunto: Re: Topband: soldering radials
> >
> > Jorge,
> >
> > Perhaps your friend's concern was that the solder joints would corrode
> > with time and galvanic action. Some have suggested using silver solder
> > to avoid this problem.
> >
> > I used just regular solder when doing radials on my 160-meter parasitic
> > array a dozen years ago and haven't observed any problem with corrosion.
> > But this may vary from climate to climate and with varying soil
> conditions.
> >
> > A simple and cheap method I have used for some verticals is to drive a
> > short scrap of copper pipe into the ground at the base of the vertical,
> > and use an all-stainless hose clamp to clamp the wires to this pipe. No
> > solder required.
> >
> > 73/Jon AA1K
> >
> > On 8/15/2011 8:12 PM, Jorge Diez - CX6VM wrote:
> >> Hello,
> >>
> >>
> >>
> >> a friend told me to not solder radials to the vertical ring/plate and
> >> between them if I am installing an array, like a 4 square. That´s
> because
> >> can catch some noise.
> >>
> >>
> >>
> >> That´s true?
> >>
> >>
> >>
> >> If yes, how can I solder them? Also if I use a DXE plate to atacch the
> >> radials, I need to solder the wire to terminals, so what type of solder
> > may
> >> I use?
> >>
> >>
> >>
> >> Do you have a type/model (or ebay link) to see what to use?
> >>
> >>
> >>
> >> Thanks,
> >>
> >> Jorge
> >>
> >> CX6VM/CW5W
> >>
> >> _______________________________________________
> >> UR RST IS ... ... ..9 QSB QSB - hw? BK
> >>
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> >
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> >
>
> --
>
>
> 73,
>
> Gary K9GS
>
> Check out K9NS on the web: http://www.k9ns.com
> Greater Milwaukee DX Association: http://www.gmdxa.org
> Society of Midwest Contesters: http://www.w9smc.com
>
> ************************************************
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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