Topband: FCP model

[Tom W8JI]

Hi Guy,

> The FCP is not resonant because it is designed specifically to
> self-cancel fields, not to be resonant.  Said another way, it's
> DELIBERATELY not resonant.

A counterpoise that fully cancels its own fields, by definiton, cannot be a 
counterpoise.
Following that logic, because it is true, the lowest loss counterpoise or 
counterpoise with lowest external field is actually no counterpoise at all.

>The May/June 2012 NCJ article on this
> counterpoise explaining how and why can be found at:
>
>   http://www.w0uce.net/Olinger_FCP_article_as_published_in_NCJ.pdf

Read it yesterday after a search. :-)

> Your assessment of the roughly opposite and equal reactances is
> certainly correct, as are the toroid vagaries. I would expect no less
> from you. So far that toroid issue hasn't mattered. People are pruning
> all shapes of inverted L, or even inverted U, into somewhat longer
> than 1/4 wave wires, to get the zero reactance point adjusted.

My thought was the toroid, because of reactance, helps cancel the 
counterpoise's reactance. Pruning an antenna is fine, so long as we are 
aware of the problems or potential problems of using a high impedance 
counterpoise system. More on that later......

> The choice of the #2 powdered iron was suggested by Sevick's work,
> picked for low loss with voltage across the winding, and has worked
> out well.  Yes, the #2 beasties DO vary on inductance with turn
> inconsistency.

I was pointing out it is a poor transformer because of leakage reactance, 
and that the resulting inductive reactance compensates the mistuned 
counterpoises capacitive reactance.

> version is uniform, of course, and we have 80 meter four squares out
> of these in what otherwise would be impossible circumstances.  I
> figure it's just a matter of time until we see 160m four squares over
> FCP's in less space than required by a single commercial method
> vertical. I tell people to use the commercial isolation transformer
> for a four square, to keep them all the same.

You would never see a recommendation from me to use one, even though there 
are many four square systems that work through sheer dumb luck. Phased 
verticals depend on equal currents in elements for null depth. In order to 
have equal currents, the Marconi type antenna MUST be fed at a current 
maximum. 1/4 wave away, the feed system requires equal voltages.

What you told me earlier is the current maximum is shifted up away from the 
antenna base to resonate the antenna system. By definition, this moves the 
current maximum away from the feedpoint.

Now with enough system loss, especially with a hybrid, you could have F/B 
ratio. But it is a very sloppy system working only by luck, and no sensible 
person would want to sell a system that depends on a series of fortunate 
accidents to work.

Four squares work best, and are optimized to work best, when the elements 
have equal currents. That means port to antenna feed distance is 1/4 wave, 
the antenna is around 30-40 ohms before mutual coupling effects, losses are 
low, and the feedline terminates exactly at the current maximum.


> The evidence of "working well" is largely anecdotal but quite
> compelling, and so far consistent. It may be that a 3 dB down
> "failure" in a comparison against a commercial grade installation is a
> brilliant success where 160 was otherwise impossible.

Most properly built antennas with small ground systems, if properly 
installed, will be within 3-4 dB of the largest systems. I find very few 
that are not.

The idea massive radial systems, even systems over 20-30 radials, are 
several dB ahead of others is just fictional....unless something was 
actually wrong with the initial system.

I see nothing compelling or concrete in any of the claims, especially 
postulations that higher scores or more RFI means we have a new verified 
science.

These are the same verifications that appear over and over again, with 
antennas like fractals, E-H antennas, CFA antennas, and so on. For example, 
one test compares a low dipole to a vertical on 160. Another compares a 
random collection of various very short wires, probably with no ground 
isolation, with a new isolated system.

I have no ADSL or RFI issues at all. Maybe that means FS levels are low? 
:-)


> It strikes me that chez W8JI might be one of those fortunate venues.
> I would be more than happy to travel to Ga with materials to put up a
> comparison supervised by both a careful skeptic and an advocate. The
> opportunity to do an academic grade comparison with known good
> antennas, including an L and other vertical radiators over the FCP,
> would be irresistible.  Wonderful NCJ article material, however it
> comes out. "The Great Georgia FCP Shootout"  :>)

Well, that's fine if it is your construction time. :-) One field strength 
test is worth 100 contest results, or comparisons to known "less than" 
antennas.

By the way, with four T-radials maximum nearfield e-field within 15 feet of 
the antenna base in all directions with 1500 watts is 27.2389 V/m RMS and 
Max H field = 0.580037 A/m RMS.

With the FCP, 97.8353 V/m RMS and Max H field = 0.0394844 A/m RMS.

That isn't etched in stone, but is a quick look. I'll expand the search 
distance and look more..... sometime.

What always happens with fields is we can change field impedance by moving 
fields around. Overall E-field goes up, overall H-field goes down.

For example a small magnetic loop moves the electric field up near the gap, 
and concentrates it in that area. If we move just 1/8th wave from the loop, 
the E and H fields are equal. Beyond that for some small distance the E 
field is actually stronger, but eventually it is like any other antenna.

We have the magnetic loop people telling us that mag loops have less ground 
loss because they have no electric field, and can be mountyed almost 
anywhere without much loss. Now it seems we have a conflicting idea that a 
magnetic field null eliminates ground losses.

I hardly know what to believe.  :-)

I think what we are really going to find is there are many ways to have 
about the same field strength in the same area, provided we don't do 
something wrong. It is more about not making mistakes, or fixing mistakes, 
than any sort of magic.

73 Tom