In a message dated 8/30/01 9:30:11 PM Pacific Daylight Time,
richard@karlquist.com writes:
<< K7GCO wrote:
>I've run patterns of verticals with radials 10 or more WL long and it
shows
>some promise. I have a location where I will be able to do that. Has
anyone any experience with this?
I don't know what program you used, but I ran
a bunch of simulations on NEC3-GS. The results
are fairly discouraging. With 10 WL long radials,
you need thousands to be effective. And even
then, you don't get all that much advantage over
an FCC ground (120 1/2 wave radials). It never
approaches the proverbial desert island surrounded
by salt water.
I also built a 20 meter vertical with closely
spaced radials 4 WL long. It didn't do anything
amazing in terms of DX performance. It is
documented at: http://www.karlquist.com/ground.pdf
Let me know if you get results that either agree or
disagree with mine.
BTW, I can make you a real good deal on 90 lbs
of magnet wire on a single spool if you want
to put out "disposable" radials!
Rick N6RK
>>
Rick: One of several favorable examples of "long radials" I know of was in
Bremerton,Wa again 35 years ago. I worked with him in Seattle--he rode the
Ferry. He wanted to compete with W7DND who was on salt water with 1/2 waves
and made them famous around here. He burried a large amount of wire into his
lawn under the road and into a big lawn of a school further on to the east
only--at night over a long period of time. He used a large full size
multiband vertical and he started working the East coast with highly improved
signal reports--no other direction. W7DND still had an edge on him most of
the time. There is no way one can equal salt water for a ground for
verticals. The Janitor was commenting one time to this ham across the street
"he was having a lot of trouble with molls."
I've heard of some other installations that have kept my interest up to give
to a try. That's why I asked for other inputs. If an idea is based on a
good concept it could or should work and doesn't, I don't get discouraged
right away and keep trying and most of the time it works out. This combined
with 1/2 wave verticals could give an edge over the rest on the ground.
Every dB less ground reflection loss and degree of lowering of the angle
helps in a contest.
In a recent post I suggested raising the base of 1/4 wave verticals 1/4 wave
or more which means you would have a 1/2 wave at least and going even higher
like with a dirigible. A 5/8 wave requires radials again and they can be
sloped down.
ka4inm@qsl.net (Ron KA4INM) replied to me with the idea of on 40M using a
100' grounded tower and J feeding it which is a great idea--no radials needed
for resonance. I want to try this on 160&80M with a wire supported by a
dirigible. It would be great for a contest. One can tap arosss the J or
feed it at the bottom of the 1/4 wave J if the right Zo. This all gets away
from all this radial dependency which had burdened hams since Brown, Lewis
and Epstien had their paper in IRE and hundreds of papers since. Enough is
enough. Lets try something new and creative. Lets try a new TT attitude of
finding what's right with a new idea rather than with all that one thinks is
wrong with it.
With the resources of many hams today they should be able to afford 1/2
waves on 160-40M as they are more effective. So many seem to locked on to
base feeding 1/4 wave verticals and supporting Anaconda Copper. Raising the
base improves performance even more. The higher the base, local radials do
far less and it may result in long radials doing far more. It's worth a try
and no one else has suggested any other possible improvement in this century.
Another idea I want to try is to drop a L network fed 160M 1/2 wave vertical
from a hot air balloon and see how well it does at different heights (miles).
The balloon doesn't have noise makers and away from the ground it could be a
quieter vertical on receive. It's certainly quiet without any jet or motor
noises. Has anyone done that? That could be very interesting. Every idea I
have tried has worked--so far. I'm on a roll.
Base feeding 1/4 waves is another dumb dumb--it's only convenient. The SWR
is around 1.5:1 without losses-lower with losses. Higher with shortened and
loaded verticals when necessary due to lot size or resources. Another
concept is to make the vertical longer which lengthens the current loop, can
raise the Rr to 50 ohms and add a selsyn driven variable capacitor to tune
out the inductive reactance--all over the band. I suggested this 50 years
ago.
Al Christman k3LC had an article in 8/98 QST of a 70' tower vertical with a
top load (he called a parasol) for resonance on 160M. The base Z's were a
bit low requiring an L network. He fed it at the top of the tower where the
Z was higher that few Mfgs have ever done. (GAP has a form of it and a rare
design improvement--finally. I have one and it works great without all these
damn radials.) I found that an 80' tower (10' longer) and a shorter Parasole
top loading would give the illusive 50 ohms feeding it at the top (tower
grounded to radials). The efficiency is about 1 dB down from a full size
vertical. This is a great design for single verticals or 4 Squares on a
budget. I'll check it out in Eznec and see if the increased mutual coupling
from the Parasols does to upset or improve the pattern.
My next project is to increase the tower height more than 80' on 160M with
the Parasol top loading (1/4 wave+) until I get the 50 ohms Rr "at the base"
at 1.9 MHz. This gives the lowest average SWR as the Rr goes lower at 1.8
and higher than 50 at 2 MHz. Likewise adjust lengths for 50 ohms Rr at 3.75
and 7.15 MHz when "longer than a 1/4 wave" using the series variableXc driven
by a selsyn. This is a way to improve efficiencies with higher Rr values.
You can cover the whole band on 80/75 by resonating a 1/4 wave at 3.6 MHz and
using the variable Xc in series at the base. Another technique I've done on
40M is to use 33' of tubing with top loading similar to the Parasol of such
length that I got 160 ohms Rr at the base. I fed it with a 1/4 wave of 92
ohms coax to match it and it used 3 short radials--that's all it needed. It
had low SWR across the band. With a 160 ohm Rr any radial Rlosses are
greatly minimized as the current is lower at the feedpoint. This is a
practical design also on 160/80M. More on that later when I compare it side
by side to a conventional 1/4 wave. It's time for hams to be a lot more
creative with their designs instead of the same old way all the time. One
way is to increase the Rr of the antenna. Think about it. It works every
time. k7gco
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