"Richard Clark" wrote in message
...
On Sat, 15 Apr 2006 12:06:45 -0400, "Yuri Blanarovich"
wrote:
As far as acting as loading element, it is another form of (real life)
loading inductance, so it is similar to loading coil, but worse performer
in
the loaded Yagi situation. Have look at the end of my article
http://www.k3bu.us/loadingcoils.htm
Hi Yuri,
Now, when we actually "look" at the design at your link, we find we
don't know much about:
Here is the information from my web site as described by Barry, W9UCW:
"Here are some actual measurements of current below and above loading coils.
92" mast, using a HI-Q coil (openwound airdux, 2 1/2"d) with small
thermocouple type meters mounted on the insulated coil support. First for
40m, moving the coil in the mast from base to center to top (with hat) and
reresonating.
Base --100ma below & 66ma above
Center --100ma below & 45ma above
Top --100ma below & 37ma above
Then, same test but for 30m
Base --100ma below & 75ma above
Center --100ma below & 60ma above
Top --100ma below & 52ma above
On a long, skinny 160 resonator with 25pf of top hat and whip, mounted on an
8' mast, I read 100ma below and 65ma above the coil.
Because of the constant claim that this must be due to the fact that the
coil is so big compared to a wavelength, I measured the in and out current
on a TOROIDAL loading coil used on a 20m mobile antenna. It was a 78" base
mast (including spring and mount) with a 38" top whip (including 12" of
alum. tubing for adjustment).
Below --100ma & Above --79ma
When I moved the coil to the top of the mast and made a horizontal "X" top
hat to resonate it back on the same freq, I got
Below --100ma & Above --47ma
So, It happens even in a totally shielded loading coil with miniscule power
going thru it! Kirchoff has no laws about current being the same on both
ends of inductors. His current law is about one POINT in a circuit and his
voltage law is about a closed loop."
.... and some significant difference W9UCW in field strength measured between
the base and center loading coil:
"The actual difference in signal strength between top and base loading of a
9' antenna is about 16 db (measured) on 75m, but Tom calculates 8db on 160.
That's because he assumes the same current in the coil. Actually it's worse
on 160 than 75."
1. How tall the antenna is (never said);
He said - 92" simulating mobile whip.
2. How long the radials are (never said);
Radials laid on the ground are non resonant, doesn't matter much, but there
were enough of them (I remember him mentioning at least 32)
3. How many turns in the coil (have to squint and count and hope);
Coild is of good quality (aka Texas Bugcatcher), what is important that it
was adjusted to bring antenna to 90 electr. degrees - RESONANCE.
4. How long the coil is (you gotta guess);
Same as 3, in each test, enough to resonante on band of test (40, 30, 80)
5. What frequency this resonates at (well, actually it doesn't say it
resonates anywhere);
Ham bands 40, 30, 80 and 160 is where they measured the currents.
6. What the drive point Z is (as if that mattered)
Not important as long as antenna is resonant on frequency in question. The
power was adjusted to show 100 ma full scale on the bottom of the coil and
read on the same type of meter on the top.
But we do know that some one can find
7. The current into the coil and;
8. The current out of the coil;
9. which according to breathless reports makes all the difference in
the world,
Picture of REALITY vs. phasors, distributed baloney, pink electrons, bla,
bla ... why it "could not be".
More appropriate assesment would be "significant", which you can judge by
his comment about 16 dB vs. 8 dB "calculated" by W8JI
Anyone can duplicate the test and verify the results and claims, instead of
displaying their ignorance of reality.
until
10. I threw away that trash coil, replaced it with a distributed load
(aka shorted transmission line) and boosted the performance.
And you did that, and measured it, right?
It has been proven in real life and measurements that "trash" coil performs
better in the loaded Yagi design that loading stub (distributed load). It
has been done, described and measured by at least three happy owners of
modified KLM 2 or 3 el. loaded Yagis on 80. Improved gain and pattern, F/B.
Interesting that the "problems" with loading coils and same current
affcionados "know it" based on their (faulty) theories. W8JI attributes his
mental state to others to "prove" his "right" which will end up being big
egg in his face.
Interesting, that question about loading stubs has "matured" to this also,
instead of providing some answers for David.
This is my last contribution to this thread.
73's
Richard Clark, KB7QHC
73 Yuri, K3BU