An 1/2WL end-fed with 1/4WL matching section is a Zepp.


Well yea, I realize that...But I think it's a silly
way to do things, if height is an issue...Unless maybe,
it's some kind of parallel stub as in a J pole...But
I would think that would be sort of silly too...
MK

The SlimJim resembles the J-Pole. The 1/4 wave section is a matching
network and it is probably not critical that it be vertical so the
height may be reduced by about 1/3. I am not sure what the folded
section does for it. but without the 1/2 wave section coming back
down from the top, the antenna is just a J-Pole.

Yea, I finally realized that, after Cecils reply.
I would still prefer a gamma loop feed I think...MK

On Mon, 28 Mar 2005 18:21:52 -0800, "John Smith"
wrote:

Interesting... so electrical length is affecting gain and EZNEC supports
it--that will probably silence those who claim the physical length is all
important... ya suppose?

Hi "Fred,"

It will take more than supposition and superstition.

So back to rote:
The physical size in relation to wavelength dominates launch
characteristics, NOT electrical length.

73's
Richard Clark, KB7QHC

"Richard Clark"
So back to rote:
The physical size in relation to wavelength dominates launch
characteristics, NOT electrical length.
__________________

I don't know who wrote your rote, but here is part of what Terman says on
this topic in his Radio Engineer's Handbook, p 795, referring to vertical
radiators driven against ground:

"Top loading has the same effect on the field distribution in a vertical
plane as a greater height. Thus an antenna for which H = 0.45 lambda can by
suitable top loading be made to have a field distribution in the vertical
plane that is substantially the same as for a vertical wire of H = 0.6
lambda."

Or is that what you meant?

RF

"Richard Fry" wrote So back to rote:
The physical size in relation to wavelength dominates launch
characteristics, NOT electrical length.
__________________

I don't know who wrote your rote, but here is part of what Terman
says on
this topic in his Radio Engineer's Handbook, p 795, referring to
vertical
radiators driven against ground:

"Top loading has the same effect on the field distribution in a
vertical
plane as a greater height. Thus an antenna for which H = 0.45
lambda can by
suitable top loading be made to have a field distribution in the
vertical
plane that is substantially the same as for a vertical wire of H =
0.6
lambda."

=============================

No, it doesn't !

But you could stretch "substantial" (a non-engineering term) a bit
more.

You have been warned once before about quoting Terman as the Bible.
(smiley)
----
Reg.

John Smith wrote:
Interesting... so electrical length is affecting gain and EZNEC supports
it--that will probably silence those who claim the physical length is all
important... ya suppose?

The important point is that the web page claim of bettering
three end-to-end 1/2WL dipoles misses by about 3 dB and a few
degrees on TOA.
--
73, Cecil http://www.qsl.net/w5dxp


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"Reg Edwards" wrote about the elevation pattern of a loaded vertical against
ground as being ~ the same as that of a longer, unloaded vertical, per
Terman:

No, it doesn't ! You have been warned once before
about quoting Terman as the Bible.
______________

I wonder, then, what your basis is for saying so.
At least I give a source.

Terman also publishes a formula to calculate the elevation pattern of a
shortened vertical with a top-mounted capacity ring, driven against
ground -- but it's too much to post here without mathematical notation. The
formula was credited by Terman to George H. Brown from his "A Critical Study
of Broadcast Antennas as Affected by Antenna Current Distribution" published
in the Proceedings of the I.R.E.

Terman also says that inserting a coil a bit down from the top of a
shortened vertical gives results equivalent to using a top mounted capacity
ring.

RF

On Tue, 29 Mar 2005 10:38:49 -0600, "Richard Fry"
wrote:

Terman also says
nothing about a Helical wound slim jim. Of course, this begs the
question "Why would he?"

The results are predictable, boringly so, and several have already
been down that road to no net gain. However, common sense in these
matters can be discarded if only someone offers validation, however
slim that may be from any jim. Such inventors stand on the shoulders
of dwarfs. Sorry for the allusion, as it again reprises the obvious
that physical height in relation to a standard (wavelength) dominates
the principle. However as principles and seeking validation go, no
doubt the topic will drift towards top loading dwarfs....

73's
Richard Clark, KB7QHC

Apparently, I am not like you, I don't have all the answers and am just
sitting here ready to educate all the poor ignorant masses who have
questions.
I am amazed my motives can even be brought into question, to the
intelligent, I have suspected would be obvious.
I am interested in what others know, or think they know--I am interested in
things I do NOT yet know..
While if I am able to help someone with information in my possession--I will
quite willingly do so, however, I first need to gain this information.
Somehow, from all your posts, I am left with the impression you were
probably born knowing all the answers and, if not, you are now in the
possession of such and, all others serve only as an anoyance to you--so I
can see how you would puzzle over some ignorant A$$ such as myself.

Regards
--
Hay, if'n ya'll cun't konstructivly partecipete in this disscusion, haw
aboot speel-checkin it fer me?


"Richard Clark" wrote in message
...
On Sat, 26 Mar 2005 18:00:30 -0800, "John Smith"
wrote:
Rather, back to my original question (your ADD--attention defecit disorder
is showing), "Anyone ever done a helical wound "Slim Jim?""

Hi "Jack,"

I suppose it has to be said if this is going anywhe Yes.

Is this 20 questions, or do you have any answers for yourself?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote:
Sorry for the allusion, as it again reprises the obvious
that physical height in relation to a standard (wavelength) dominates
the principle. However as principles and seeking validation go, no
doubt the topic will drift towards top loading dwarfs...
_____________

So far you have not provided support for your statements on this subject
from any recognized antenna authority. Do you really believe that your
understanding of this, and your statements about it are better/more accurate
than those of Frederick Terman and George Brown?

RF