On 09 Feb 2004 01:12:18 GMT, oUsama (Yuri Blanarovich)
wrote:

About as much as current taper in a coil.

Uh, Huh, Huh
yeah, I thought that was good too. ;-)

Mark Keith wrote:
"Start with a center load. Note the current taper. Then place the coil
below the midpoint level. Note the current taper."

Mark may want an indication of the better site on a too-short whip for a
loading coil. John Devoldere, ON4UN shows what he`s found in his book
"Low-Band DXing". On page 9-14 John says:
"It is clear now that the real issue with short verticals are EFFICIENCY
and BANDWIDTH. -----Therefore maximum attention must be paid to these
terms by:
Keeping the radiation resistance as high as possible
Keeping the losses of the loading devices as low as possible"

John gives radiation resistance formulas for base loading, top loading,
center loading, combined top and base loading, and linear loading.

John says on page 9-19:
"The rule for keeping the radiation resistance high is simple:
Use as long a vertical as possible (up to 90-degrees)
Use top loading

Low-Band DXing is worth checking out.

Best regards, Richard Harrison, KB5WZI

Cecil Moore wrote in message
Then you disagree with the guys who say it has no taper. Guess what,
Mark? That puts you on my and Yuri's side of the argument.

Maybe so, but I place much less importance on this than he does.

You may also place less importance on strawberry ice cream than
he does.

I probably would. There are many other flavors I like better...

To me, it means very little, if anything.

Yuri was accused of "Repeating misleading information". Here is
a typical response to one of Yuri's postings:

"You like to call names, insult people, and argue rather than take
the time to learn basic electronics. ... If you look at HOW an inductor
works, the current flowing in one terminal ALWAYS equals the current
flowing out the other terminal."

Note the word "ALWAYS". The ad hominem attacks upon Yuri is probably
one reason he considers the subject to be important.

Thats fine, as long as he doesn't try to convince me it is. I have no
problem with anything he is doing. My only objection is to the early
claims that this amounts to gross error when modeling. It surely does
not. I'm not sure if he still believes this gross error exists or
not... MK

oUsama (Yuri Blanarovich) wrote in message
So now it's 0.51% efficient instead of only 0.49% right? [g]


Nope, more like going from not getting answers to my calls or CQ (S0 or less
:-) to getting reports from W6, through P4 to Eu of S6 to S9. Even getting hell
from W8JI for wiping out - QRMing the DX window.

The noise has been fairly low lately. How was the noise with the old
version? How long ago was that?
An A/B test would be needed to form an accurate conclusion. But I
don't doubt you saw an improvement if you raised the coil or added a
hat...

You learned heads figure out the efficiency improvement in dBm, uV or dB or S
units. It may not jive with your decimal points, but is OK with me.

In the past Cecil showed some results from mobile antenna shootouts, where
simple change in position of the loading coil can mean dBs or tens of dBs
difference. Might not be reflected in your modeling results, but reality
speaks. Those who built and used the stuff know it. Those who calculate it
"know better"?

But! What does this have to do with the "current taper" debate? All
you are doing is applying practices that have been in use for years. I
was doing what you are doing about 14 years ago when I first got a
mobile radio. I've been using lower "add on " masts to boost coil
position since nearly day one. It was common knowledge even back then.
It doesn't really matter what the taper is across the coil, you still
are probably trying to get it as high as you can before coil losses
get too severe, and use as much top hat as you can. "If you use a
hat". I think appx 75% up is about as high as you would ever want to
go with a coil. You can use Reg's vertload and find the best position
to a degree of accuracy that would never be noticed on the air. 50% up
is very close behind in performance. Mine is 55% up " 10 ft center
load" when driving, and about 64% when parked and using the extra 3 ft
mast at the bottom. "13 ft with coil about 8.5 feet up". Sure, I could
jump it up to 70-75% , but it's not worth the hassle of whacking the
coil on every tree I pass. My coil is over 9 ft off the ground even in
the shorter 10 ft driving mode. Add three to that when parked.
I fully agree with elevating the coil position of short low band
verticals, but this is ancient news. What does the current taper, or
you knowing about it or measuring it, do to further improve the
antenna over what it would be anyway? It wouldn't effect me. I've
already got mine as high as I can get it without a major mast
overhaul.


This is getting amusing and eye opening how many flat earth society members are
out there. Keep on harping!

I'd rather be a flat earther than have delusions of a small current
taper across a loading coil really amounting to anything important,
other than maybe settling a ****ing match with Tom. :/ It's not going
to change a thing in the real world because the optimum coil positions
are already known, and have been real world tested with FS tests.
Taper, or no taper. Just because you declare we have current taper
across the coil, does not mean anything is going to suddenly change.
It's just something to think about.
It's like worrying about the current taper on a dipole. Knowing about
it doesn't mean you can really do anything to further improve the
antenna. Some say CCD antennas are better, but I'm not convinced after
listening to quite a few over the years. I usually had a better
overall signal with my old fashioned "flat earth" coax fed dipoles,
than they did with their "new fangled" CCD antennas. Coil placement
can effect loaded dipoles and yagi's, but again, ancient news.
But anyway, glad to hear you are finally getting around to applying
these old commonly used practices to improve your antenna.
They haven't kept you locked away in a closet the past few years have
they? I keep getting visions of mushrooms... :/ MK

On 8 Feb 2004 22:41:28 -0800, (Mark Keith) wrote:
I keep getting visions of mushrooms... :/ MK
And a Hookah smoking caterpillar? [a nod to "Jefferson Airplane" and
Lewis Carrol]

In any case, we went round over this moving the load in the opposite
direction many months ago (nothing's changed since then either):
My model took no more than a minute to offer (in comparison to the
like data already offered in response to your other post):
1 W2E1 1 0.00
2 .94658 0.00
3 .90287 0.00
4 .86518 0.00
5 .83014 0.00
6 .79686 0.00
7 .76486 0.00
8 .73383 0.00
9 .70357 0.00
10 .67393 0.00
11 .64482 0.00
12 .61614 -0.01
13 .58783 -0.01
14 .55984 -0.01
15 .53212 -0.01
16 .50463 -0.01
17 .47734 -0.02
18 .45021 -0.02
19 .42323 -0.02
20 .39637 -0.02
21 .36959 -0.02
22 .34288 -0.02
23 .31623 -0.02
24 .2896 -0.03
25 .26298 -0.03
26 .23634 -0.03
27 .20966 -0.03
28 .18292 -0.04
29 .15608 -0.04
30 .12912 -0.05
31 .102 -0.07
32 .07466 -0.09
33 .04706 -0.14
34 .01911 -0.32
35 .00929 -179.4
36 .03832 -179.9
37 .06839 180.00
38 .10011 180.00
39 .12989 180.00
40 .15719 180.00
41 .17431 180.00
42 .18799 180.00
43 .19776 180.00
44 .20299 180.00
45 .20331 180.00
46 .19816 180.00
47 .18701 180.00
48 .17804 180.00
49 .17045 180.00
50 .16365 180.00
51 .15741 180.00
52 .1516 180.00
53 .14614 180.00
54 .14097 180.00
55 .13604 180.00
56 .13133 180.00
57 .12679 180.00
58 .12241 180.00
59 .11817 180.00
60 .11405 180.00
61 .11005 180.00
62 .10614 180.00
63 .10233 180.00
64 .0986 180.00
65 .09494 180.00
66 .09134 180.00
67 .08781 180.00
68 .08434 180.00
69 .08091 180.00
70 .07754 180.00
71 .0742 180.00
72 .0709 180.00
73 .06764 180.00
74 .06441 180.00
75 .06121 180.00
76 .05804 180.00
77 .05488 180.00
78 .05175 180.00
79 .04863 180.00
80 .04553 180.00
81 .04243 180.00
82 .03935 180.00
83 .03626 180.00
84 .03318 180.00
85 .03009 180.00
86 .02699 180.00
87 .02387 180.00
88 .02073 180.00
89 .01754 180.00
90 .0143 180.00
91 .01096 180.00
92 .00748 180.00
93 Open .0035 180.00

The solenoid was dropped 10 inches between the two models.
Best gain = -15.33dBi @ 29 deg for this
Best gain = -9.52dBi @ 29 deg for the former

Lowering the coil led to nearly a 6dB drop - real world stuff and part
of the ham lore as you point out.

All this data pointed out then the current "peak" as has been
confirmed recently.

73's
Richard Clark, KB7QHC

Richard Harrison wrote:
John says on page 9-19:
"The rule for keeping the radiation resistance high is simple:
Use as long a vertical as possible (up to 90-degrees)
Use top loading

I arrived at the same conclusion many years ago by assuming the
current taper in a 75m loading coil would be maximum when the coil
was as far away from the feedpoint as possible. Using that assumption
and a few free parts from my junk box, my top loaded mobile equaled
the best of the best (and most expensive) at one of the CA 75m
shootouts. And that was with a pretty small capacitive top hat.
--
73, Cecil http://www.qsl.net/w5dxp



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Mark Keith wrote:
My only objection is to the early
claims that this amounts to gross error when modeling.

Again, you two may be using a different definition of "gross".
I would say a 20% error in the estimation of current at the
top of a loading coil is a pretty gross error. Your opinion
may differ.
--
73, Cecil http://www.qsl.net/w5dxp



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