Yes, FCP *was* originally designed to get small-lotters on top-band. My
buddy Jack downsized and tore my heart out with his moaning about what he
had done to his 160 results. But watch out when you say "just". FCP has
opened Pandora's box on the murky area of counterpoles for 160. We have
the Reverse Beacon Network. And you will be hearing 160 4 squares built
with FCP's, taking up less space than one conventional 1/4 wave vertical
with 1/4 wave radials, eliminating the issue of what to do with crossing
radials. And yes, there is a way to do this with grounded towers. There is
a lot of stuff going on and gaining speed.
Cat is out of the bag, boys. No going back.
Short version:
1) All NEC based modeling programs have issues estimating ground losses.
They are indemic, and may be unsolvable.
2) Using NEC based programs generating antenna patterns to estimate radial
or counterpoise efficiency is NOT reliable.
3) Skywave comparisons using USA-wide and world-wide Reverse Beacon Network
(RBN) ARE available and are increasingly pointing toward results that NEC
programs currently poorly estimate.
4) Method for viewing RBN results
5) There is hope.
Long version:
The difficulty in comparing these antennas, comes in the weakness of either
NEC2 or NEC4 based programs, including the professional version of EZNEC
running the NEC4 engine, to properly estimate ground losses. The problem
is that the ground method (Norton Sommerfield) can only use a monolithic
completely uniform and homogenous ground material in its calculations, and
cannot deal with layering or miscellaneous variations in real ground, nor
with increasing water content with increasing depth, or a water table, all
nearly universal components in any actual dirt beneath our feet, especially
in building lots that have been graded and filled with "leftover" fill from
other locations to provide a flat building surface or lawn area.
Roy Lewallen, the author of EZNEC, finally was the source of my
confirmation on this, though I suspected as much for quite a while. He
simply states that the model UNDERESTIMATES the ground losses. He has real
work with W8JI on this which he has not published, for whatever reason. I
suspect that if he had the issues identified to his academic standards, he
would publish, but that is a guess.
In my mind, the original overwhelming persistent anecdotal indicator of
such a modeling problem is the inability of any NEC model to predict the
usually excellent success of an end-fed 80m halfwave L. In fact the models
portray the EFHW as a significantly inferior choice to an inverted vee with
the apex at the same height as the bend in the EFHW. Experience does not
bear that out. I will rest easier when something in the modeling world
shows what has gone on all my life with that antenna.
In the mean time we are stuck that we don't have properly calculated losses
for dirt underneath. Where there is this much smoke there is fire
somewhere. Draw conclusions from NEC modeling programs embedding losses in
gain figures at your own risk.
We actually do have sky wave comparisons of different types of
radials/counterpoises via the Reverse Beacon Network.
Hard to say how many FCP based antennas are out there now, but the
commercial FCP isolation transformer from Balun Designs is selling well.
Last look, W0UCE's web page that describes the FCP (
http://www.w0uce.net/K2AVantennas.html) continues to average 70 hits a day
from all over the world including such places as China and Indonesia.
Wireman sold out all his double polyimide #14 wire used for hand-winding
the transformer and had to scramble to restock. I've answered well over a
hundred direct inquiries on variations on its use. It's clear that people
are adapting the FCP to their own circumstances.
*
*
If you want to see measurements, go to the reverse beacon network and look
up K2AV, N1LN, N4XD, WX4G, W4KAZ for Jan 28 and 29 2012 (CQ160CW). All
were QRO except W4KAZ who was running 100 watts. So adjust KAZ up 13 dB.
All are in the general Raleigh area. AV and KAZ are over FCP's. XD and
4G are over radials, XD for sure a decent set of radials, not sure of
WX4G's system. LN was multi-op, and has two phased verticals using ON4UN
style loaded 1/8 wave elevated radials. WZ7I is the reverse beacon site
which seems to have least amount of fading from our Raleigh area and is
probably the best "first hop" RBN for measuring plain sky wave power. The
"poor propagation" high absorbtion night of 28 Jan and WZ7I gives you a
very steady all night comparison. There was almost no Europe heard by
anyone in SE US Jan 28Z. Jan 29 was much better for Europe and seeing
spots from here. Spots from GW8IZR are telling for transatlantic
performance. To see how modest antennas stack up against the "best of the
best", add K3ZM to your comparisons. His contest station has a 160 meter 4
square over a salt marsh at the edge of salt water in directions north
through east through south. There are some comparisons where you can see
him switching the direction of his array.
To see this, go to http://www.reversebeacon.net/ Mouse over "DX Spots"
pulldown, then click on "Spot Analysis", pick a date, a continent then
spotting station from that continent, then type in stations lower left.
160 meter spots are at the bottom.
What you have is a robot that is just writing down call signs and signal to
noise ratios. It is all sky wave. They have no way to discern whether the
transmitting antenna is a K3ZM monster or a super cooled wet noodle. All
it has is signal to noise when it copied the call sign.
Get good at using RBN before you decide how good an FCP (or any other
antenna configuration) is or is not. Some of us are scrambling to explain
some altogether too good results. The readers can draw their conclusions
on RBN.
There IS some progress in getting something useful for ground estimation in
NEC. The technique is to summarize underground near field values from the
program times cubic meters underneath and do the integral calculus in
EXCEL, going on the basis that for a given set of dirt, what you want to do
is to minimize the field in the ground. That will compare ground losses,
and possibly allow some useful interpolation with perfect ground
comparisons. I am working on that and will hopefully have something out
before too long.
73, Guy.
On Sat, Feb 11, 2012 at 3:51 PM, Rik van Riel <riel@surriel.com> wrote:
> On 02/11/2012 01:12 PM, k2qmf@juno.com wrote:
> > Hi Jack,
> >
> > Are you saying that the FCP works just as well as
> > an elevated or buried radial field???
> >
> > I was under the impression that the FCP was just a way
> > to get on 160 when there wasn't room for a radial field...
>
> The FCP, and also the double L antenna, work as well
> as the (poor) radial systems that many people can put
> up.
>
> It will not outperform a proper radial field with many
> dozens of quarter wave radials.
>
> According to NEC (which I know is not very accurate),
> both the vertical with FCP or a double L antenna are
> about 6dB below the output of a vertical over perfect
> ground - which a vertical with 120 quarter wave
> radials gets fairly close to.
>
> If you cannot fit a large radial field in your yard,
> and would be making do with a small one anyway, it
> may be worthwhile to just lift the whole antenna off
> the ground.
>
> This may lose you 1-3 dB over a good vertical with a
> smaller radial field, with the benefit of coming
> relatively close without having to dig up your yard.
>
> If you have the space and care about your signal
> strength, you'll probably be better off with a full
> radial field.
>
> --
> All rights reversed.
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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