"Dave" wrote in message
news

wrote in message
oups.com...

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

On Thu, 20 Apr 2006 22:18:31 -0400, "Yuri Blanarovich"
wrote:

Richard can search for that "no good" article in CQ
Mag. and query them

Hi Yuri,

That's got to be a recommendation! You can't remember the
particulars, you can't remember the name, and I have to carry your
water. You sound like a Washington bureaucrat in the White House -
"Trust me! I'm here to help you with your Social Security." [It will
be made as easy as the new drug benefit.]

Now THERE's a standard of efficiency and performance that has been
"proven." ;-)

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 20 Apr 2006 22:18:31 -0400, "Yuri Blanarovich"
wrote:

Richard can search for that "no good" article in CQ
Mag. and query them

Hi Yuri,

That's got to be a recommendation! You can't remember the
particulars, you can't remember the name, and I have to carry your
water. You sound like a Washington bureaucrat in the White House -
"Trust me! I'm here to help you with your Social Security." [It will
be made as easy as the new drug benefit.]

Now THERE's a standard of efficiency and performance that has been
"proven." ;-)

73's
Richard Clark, KB7QHC


That's right, for me it was enough to remember the results. If you want more
info, you can Google it or SeeeKeeew it. You ain't paying me and for free
advice this should do it.

If I wanted to get details and build the coils, I would dig for it. For now
I have better idea for loaded loop antenna, so it is on the back burner.
Now you are mixing Washington in addition to Fractals - not very good
picture of your "fakultys" if you have to rely on social security. Any
constructive ideas besides filibusters and "Bush- baaad"?

Sayonara!

73 (doesn't need 's - they are included) - if I was nitpicker like you :-)

Yuri, K3BU/m

On Thu, 20 Apr 2006 23:17:51 -0400, "Yuri Blanarovich"
wrote:

That's right, for me it was enough to remember the results.

Hi Yuri,

Folks remember dreams pretty much in the same way. You wake up
astonished with the revelation, and forget the details before you
throw back the covers.

73's
Richard Clark, KB7QHC

Michael Coslo wrote:



Is there a beer called Budweiser now? Hopefully one to replace that old
PeeWaa that was sold under the same name! ;^)




darn stuff could give me a headache and make me queasy after one
can..... ick.


- 73 de Mike KB3EIA -

That's the additives. Lots of people get headaches from AB products.
I'm not sure which additives might do it, but boss probably does. He is
very much into making homebrew. Even has a kegging system.

Odd as it may sound, the pumpkin beer he made last fall was absolutely
delicious.

tom
K0TAR

"K7ITM" wrote in message
oups.com...
So Dave, have you built a NEC model of the antenna? Do you know that
the loading stub really has unequal currents on its two legs? Since
that current is fairly close to the element itself, is the net current
(the antenna current) on the stub in phase with or out of phase with
the element current? What about the efficiency reported by NEC--if you
use zero loss conductors versus the loss of the actual aluminum used in
the antenna?

no, i don't own nec, and don't know enough about it's methods or limitations
to trust just throwing together a model to play with on any free version i
could get. i have done enough modelling professionally with tools like
ansoft/maxwell (for quasi static e-fields), EMTP (for power line
transients), TFlash (for lightning transients on power lines), Simulink and
EASY5 (electro-mechanical control systems), and some other tools, that i
know that if you don't know your tool and it's limitations that any result
you generate is questionable. besides, i have enough other things to do
this summer putting up new antennas and using them... not enough time to
second guess every design out there, I made my choice and I'll take my
chances... but the 40m4LLDD i put up last year at 105' seemed to work well
over the winter, and much better than the 40-2cd it replaced.... (compared
over almost a year now against another 40-2cd that hasn't been moved)... so
now i'm replaceing the other 40-2cd with a second 40m4LLDD at 175'. if
nothing else it will look impressive, and thats worth 3db or more in the
operator's belief that they are loud.