John Smith wrote:
Gene Fuller wrote:

...
The patent, US 7187335, is a real hoot. I especially like the part
where he describes doubling the bandwidth by adding a parasitic
winding intertwined with the base coil helix.

Do you suppose his antenna is in equilibrium? Could proper application
of Artsian-Gaussian theory improve it even more?



73,
Gene
W4SZ

What? You don't see cutting the capacitance between winding turns as
causing some measurable effect which in turn affects a property of the
antenna proper?

Thicker conductor(s) usually means a measurable gain in bandwith, with a
parasitic element in such close proximity to the major element, a gain
in bandwidth is not that difficult to propose and attempt to
prove/disprove.

Regards,
JS

John,

The effects you mention may have some impact on bandwidth, but they
don't double it. And the capacitance probably increases, not decreases.
Placing an extra conductor between two capacitor plates increases the
capacitance. At the same time placing a grounded shield between two
capacitor plates reduces or eliminates the coupling between the original
plates. It is not clear to me which effect would dominate in this case.
In either case it is unlikely to be very important.

Lots of people understand how to make an antenna broadband; simply add
resistance. This is not always "bad". It is merely a choice.

Just for grins I did a little EZNEC experiment. I started with a base
loaded monopole that used a generated helix as the loading coil. I
adjusted and resonated the system to SWR = 1 and took a look at the
bandwidth. I arbitrarily took SWR = 2 as the bandwidth limits. I then
added a parasitic winding between the turns of the helix. This winding
was not connected to anything. I reran the simulations.

What I found was interesting, but not surprising.

When the wires were treated as lossless, there was virtually no
difference in bandwidth or any other parameter. The parasitic winding
had essentially no impact.

When I changed the wires to copper, the bandwidth increased in both
cases. However, in the case with the parasitic winding the new bandwidth
was 2.5 times as large as the case without the extra winding. The
resonant input impedance was also about 2.5 times larger.

There is only one plausible explanation for this observation. The
parasitic winding adds loss to the antenna system. I won't claim this is
"bad". Depends on the characteristics desired.

The bottom line is that there is no wondrous invention here. Either
Vincent knew about this effect and chose to ignore it, or he did not
understand what was happening. The capacitance explanation is just baloney.

73,
Gene
W4SZ