"Dave" wrote in message
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Dave wrote:
finally someone said something that makes sense in this thread... but no
one
has addressed my original question directly... but i guess that is par
for
the course in here when this group gets wound up, everyone goes off on
their
own little tangent and starts attacking each other.

I tried to, but I see it did no good at all.

I have a Force 12 80 and 40 meter linear loaded Yagi.

The Q of the loading sections are terrible. They are thin aluminum wire
of some sort of alloy that makes them hard.

For the typical reactances produced by that loading system Q (reactance
over ESR) is well in the sub-100 range.

That's why you can take even a fairly poor loading coil, replace the
linear loading, and have the same perfromance. Or you can make a good
coil, like airdux or BW stock with number 12-14 wire, and make the
antenna work better (IF you can keep it from falling apart in the
wind).

The results of linear loading depends on where the linear loading is
installed and how it is constructed, but the general rule is if you
take the very same size and material conductors and wind a coil it will
work better.

Now I suppose we can talk about UHF antennas, 1/2 inch copper tubing
stubs, Cecil's imaginary reflected waves, quote Harrison's book
collection.....but that's how the Force 12 linear loaded 80 and 40
meter antennas I have work.

That's why they are laying in a pile with waddled out holes near the
rivets and all that lossy linear loading wire wrapped up in a ball,
waiting the be rebuilt into good antennas.

73 Tom

so why would a company like m2 go with linear loading over the much
simpler to build coil? and how in the world do you measure the Q of the
loading section when it is a large percentage of the size of the element?
Does Q even really mean anything in a system that is radiating? Since
some of the energy is being radiated along the length of the loading
segment i would expect it to look very lossy compared to a small coil.



Dave,

it boils down to the "problem" we were rehashing here - distribution of
current along the antenna element. I tried to highlight that, but it gets
lost in the "contributions" of the "same current worshippers".
If you would model loaded element with 1. lumped inductance, 2. real
solenoid and 3. loading stub - wires folded back onto element, you would see
the variations of current distribution along the element and its effect on
the design or optimization of multielement Yagi (cancellation in overlaps).

The reason why antenna manufacturers used loading stubs to shorten the
elements, was the idea that it would be less loss (it's "just" a wire) and
would be more efficient than "some" lossy coil. You hardly find commercial
loaded Yagi with coils as a loading element. They all used "nice, efficient"
loading wires until W6 - I forgot the call, wasn't happy with performance of
his 80m KLM loaded Yagi, replaced the "efficient" loading stubs with good
quality coils and found that antenna performed much better. Better gain,
better pattern, F/B (Richard can search for that "no good" article in CQ
Mag. and query them). Few other hams did it too later and found the same.

This is another proof of difference in performance when considering the
proper loading and proper treatment of load in the standing wave (antenna)
environment.
The effect gets magnified in multielement arrays and has significant impact
on the pattern and F/B. This is why we are arguing about proper treatment of
the current distribution along the loaded element. How can it be the same in
a coil, when it is demonstratively different in the loading stub (EZNEC
shows THAT). When you have "wire" folded on itself three times and affecting
currents (cancellation) along them - it gets worse than just current drop
along the loading coil. The unbelievers would try to tell you that there
can't be drop of current along the coil, much less along the loading stubs
(it's just a piece of wire), but if you consider standing wave environment
along the antenna element, then it all becomes clear and explains the
behavior of various loading elements, current distribution in them and
effect on the element and array. So replacing loading stubs with good
quality coils WILL improve the performance of loaded Yagi, gain and
especially give you better pattern and F/B. The same goes for Beta match at
the center of element as used by i.e. Hy-Gain 402BA, replace it with few
turns of copper tubing to get 50 ohm match to the coax. Now there is good
fiberglass tubing available that can be used for strong insulators and forms
for the loading coils.

Standby for W8JI mumbo-jumbo, bla, bla, bla.... he has to be the last
standing "trutz" man! You can verify and decide.

73 Yuri, K3BU