Below is a link to a performance comparison of a DLM antenna with two other
electrically short radiators, and to an unloaded 1/4-wave monopole.

http://i62.photobucket.com/albums/h8...omparisons.gif

RF

Richard Fry wrote:
Below is a link to a performance comparison of a DLM antenna with two
other electrically short radiators, and to an unloaded 1/4-wave monopole.

http://i62.photobucket.com/albums/h8...omparisons.gif

RF

Interesting.

What URL did you get this data from, exactly?

And, I take it you are comparing a 1/4 wave DLM against a 1/4 reference?
Why not compare a 1/2 DLM against a 1/4 wave reference, there physical
lengths are MUCH MORE similar?

Regards,
JS

"John Smith" wrote
Interesting. What URL did you get this data from, exactly?

The data for all but the DLM I generated myself in NEC. As I wrote in the
study, the DLM data came from the U.R.I. test report, of which I have a
printed copy.

And, I take it you are comparing a 1/4 wave DLM against a 1/4 reference?

The physical height of the 3.5 MHz DLM was not 1/4 of a free-space
wavelength. The test report states that it was only 33% as tall as that.
This is the reason that the other two short radiators in the study were set
to that height.

Why not compare a 1/2 DLM against a 1/4 wave reference, there physical
lengths are MUCH MORE similar?

Because the claim has been made that the standard DLM is the equivalent of
an unloaded, 1/4-wave monopole when both are used with the same r-f ground.
Investigating that was the purpose of the exercise.

RF

Richard Fry wrote:

...
Because the claim has been made that the standard DLM is the equivalent
of an unloaded, 1/4-wave monopole when both are used with the same r-f
ground. Investigating that was the purpose of the exercise.

RF

The first DLM I constructed was 1/4 wave, it convinced me I should
attempt the 1/2 wave version ... the 1/4 wave version DOES make a great
stealth antenna--10m version 2'+" .

The 1/2 wave version 5'+" , a 1/4 10m reference = ~8'.

Due to the lower takeoff angle of the 1/2 wave DLM, it compares much
more favorably with the physical length of a 1/4 wave reference
antenna--and is actually of a shorter physical height.

No single antenna is the solution for all real world situations.
However, I have no bone to pick with any particular antenna(s) or
personalities ... I only have needs which particular designs may offer me.

Strange how the DLM is a VERY GOOD solution to some real world
problems/situations and that, since it is considered "unconventional",
causes so many to turn a blind eye.

Who says the DLM is the best construction in this particular direction
of physically short antennas, perhaps it can be engineered to even
greater performance--however, to do so would require an atmosphere of
experimentation, trial-and-error, etc. which was in the ORIGINAL
purposes of the amateur radio service ... too bad so many forget.

Regards,
JS

On Wed, 28 Nov 2007 08:56:12 -0800, John Smith
wrote:

Strange how the DLM is a VERY GOOD solution to some real world
problems/situations and that, since it is considered "unconventional",
causes so many to turn a blind eye.

Hi Brett,

Strange you should say that... is more the issue.

Who says the DLM is the best construction in this particular direction
of physically short antennas, perhaps it can be engineered to even
greater performance--however, to do so would require an atmosphere of
experimentation, trial-and-error, etc. which was in the ORIGINAL
purposes of the amateur radio service ... too bad so many forget.

Generally "who" at the start of a sentence introduces a question which
here above seems to have trailed off into weepy sentimentality.

I don't suppose you have any metrics for any of these observations you
purport to have made? Like how many have forgotten? Or naming "who"
of "who says the DLM...." (now that is certainly strange as it is so
obviously Vincent, Art and yourself).

Stranger yet is how it can be engineered to even greater performance
when it claims to better a radiator that achieves efficiencies in the
90s of percent. The dewy-eyed adulation of "greater" celebrates a
munchkin as goliath where this pygmy performer is gnawing on ankles to
keep our attention.

I simply wonder if you put RF to it, and unfortunately used hollow
tubes to construct it, what size fuse would Arthur claim it would
blow? You guys certainly struggle to support your observations with
practical, technical details.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

...
73's
Richard Clark, KB7QHC

As always Richard, let others who have gone before you tell you what is
possible/impossible, works/does-not, what-is-to-be-done/what-is-not, etc.

And further, let those of such a weak mind as to listen to you, follow
you--I choose my own path ... the universe is, undoubtedly, unfolding as
it should.

Thank you kindly ... ;-)

Regards,
JS