Hi All,

This is a variation on themes being played out. As the title
suggests, you too can force your modeler to give you phenomenal
results in just 5 minutes! Think of it, 20 dBi from a short Dipole -
but first the story:

While I was pondering the coil current flow tricks, I mused over the
thought of instead loading a short antenna with the inverse of
inductance, capacitance. Instead of using suspect lumped loads, I
instead chose to load the wire with insulation. And not just any
insulation.

Insulation found on typical wire comes in a vary small range of
values. They exhibit dielectric constants from 2 to 4, and rarely
that high. If I were to take a load of it, say in the form factor of
a Texas Bugcatcher coil - what would happen?

Not much it seems. However, I am not one to let that slow me down and
I considered a list of elements and materials to examine them for the
highest DCs available. I was thinking of waxes primarily. The
thought ran that I would turn a small HF antenna into a candle and see
if that would slow the Vf.

Waxes do offer higher DCs, but not markedly so. I started to think
salts next, considering that the common round salt box was about the
same size as a large coil. Salts have a high DC (up to the teens),
but even there, not much effect.

Then I turned to what is commonly available, and exhibits a very high
DC - water (dielectric constant of 80). I started with a meter high
tube of 4 inches diameter (been thinking a lot about plumbing this
week when contractors built a French drain in the basement) and
plunked a short (5M) vertical antenna into it.

THIS made a difference. (OK, so did others, but not like THIS).

What the hell, I started to make the diameter bigger to see where the
limits of failure were. Turned out to be around 12 inches thick water
jacket. This was for a monopole in a truck bed I though (fair amount
of weight and sloshing in this linear load). However, it had the
intended consequence of providing 5.6dBi gain.

Now, this gain has to be taken in the perspective of the unjacketed
radiator that exhibits -4.85dBi gain. More than 10dB gain by adding
this water jacket! Hosanna! Of course, if I trimmed this thickness
to goose up the gain, THEN the modeler failed with reports of negative
resistance (due to possible problems that could not possibly exist).

Well, time to reduce complexity and do the same thing with a short
dipole in space (10M long excited at 3.8MHz). This antenna is
constructed with 10 wires so that only the first wires closest to the
feed are insulated. I increased the size of the water jacket and
noted results for drive point impedance, average gain, and best gain.
The binomial progression is edited from a longer list. The results
are as follows:

Thickness Zfeed AvGain Gain
mm Ohms dB dB
0 4.1 - J 1646 -0.02 1.77
10 3.726 - J 1437 0.039 2.17
20 3.498 - J 1305 0.66 2.45
40 3.2 - J 1133 1.05 2.83
80 2.848 - J 930 1.55 3.34
160 2.46 - J 705.8 2.19 3.98
320 2.051 - J 469.5 2.98 4.77
600 1.67 - J 249.5 3.87 5.66
1211.67 1.238 - J 0.0013 5.17 6.96
2200 0.8685 + J 213.2 6.71 8.5
4000 0.4971 + J 427.7 9.13 10.92
8000 0.0656 + J 676.9 17.93 19.71

As you can see, a water jacket 16 meters wide around the first
meter(s) of the dipole offer considerable gain and nothing suggesting
that further enlargement was going to upset this trend. I wasn't
going to push it anyway because it looked exceedingly suspicious.

As suspicious as it may appear, it shows a rather smooth progression.
It was pleasing to note how the load reactance shifted from capacitive
to inductive. I posted a note to Roy who confirmed the intent for the
insulation entry was to limit it to common coating dimensions.
However, there is nothing in the data to suggest a logic breakdown in
my progressions.

On the other hand, when I pushed this further by reducing the wire
size (10 wires per element instead of 5, while keeping the same total
length), I noticed the effect was more remarkable:

Thickness Zfeed AvGain Gain
mm Ohms dB dB
1000 0.2847 + J 139.9 10.98 12.76

A 1 meter water jacket on a shorter wire induced more gain than the
former 4 meter water jacket from the series of results above.

To me, this suggested a boundary violation more so than a thickness
failure mechanism. There are cautions or prohibitions in connecting
different size wires, it seems that extends to insulations' diameter
mismates even when the wires' diameters (25.4mm) are identical
throughout.

So, the object lesson seems to be
Do not try this at home,
or
in the back yard;
or
Do not fill your truck bed with water flooding your HF antenna

73's
Richard Clark, KB7QHC

p.s.
Just in case there is nothing wrong with the model, I hereby cede this
to the public domain and this is notice of prior art.