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Old December 30th 08, 02:00 PM posted to rec.radio.shortwave
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Default Shortwave Radio Listener (SWL) Antennas -versus- Amateur RadioAntennas

Telamon wrote:
In article
,
Telamon wrote:

In article ,
Dave wrote:

John Smith wrote:

However, in side-by-side comparisons on 10-6-2m antennas I have built,
comparing a 5/8 against the 1/2 (construction methods/materials and
matching components identical) ... the actual difference, in the real
world, must be less than the width of a meter needle in the readings ...
or, put simply, I no longer deal with the extra length required of the
5/8 ... your mileage may vary ...

The advantage of a physical height (antenna length) between 180 and 215
degrees (see previous post regarding the magic number being around 195
degrees) is improved take-off angle and reduced skywave-groundwave
interaction, not dramatic nearfield voltage increases.

Regarding Mr. Smith's comments above my experience and others is the
opposite. 5/8 is a much better performing antenna than a 1/2 wave for
local VHF and UHF communications. Well worth the effort to build a 5/8
wave antenna over a 1/2 wave. The 5/8 had some kind of series load coil
part way up the whip where the 1/2 wave match/compensation was done at
the base so the whip was solid. Sorry I can't more specific then that as
those experiments were many years ago.

Mr. Smith is still lost in space.


Here is an example of the 5/8 wavelength antenna I recall using in the
center of the page. The one I used was permanent mount not magnetic
though. The van roof it was installed on was the ground plane.

http://www.new-tronics.com/main/html/mobile_vhf.html

When this antenna was changed for a 1/2 wave a lot of coverage was lost.
This was before cell phones so I had to start using pay phones a lot.


The one with the center coil is a collinear. It is 2 stacked verticals
with a "delay" between.
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Old December 30th 08, 06:25 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Nov 2006
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Default Shortwave Radio Listener (SWL) Antennas -versus- Amateur RadioAntennas

Dave wrote:

...
http://www.new-tronics.com/main/html/mobile_vhf.html

When this antenna was changed for a 1/2 wave a lot of coverage was
lost. This was before cell phones so I had to start using pay phones a
lot.


The one with the center coil is a collinear. It is 2 stacked verticals
with a "delay" between.


If I remember correctly, from running comparisons thought antenna
prediction softwares, 1.5db is about the most "gain" which can,
theoretically, be had between a 1/2 and a 5/8; and, not even "all that
gain" (i.e., max 1.5db) is gained in such a narrow point or swath of
pattern so as to account for "a lot of coverage lost." And, rarely, if
ever, is the theoretically reached, in my humble experience.

Something is obviously wrong with that whole statement ... perhaps a
"chit poor" 1/2 is being compared to a reasonable performing 5/8?

Regards,
JS
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Old December 31st 08, 09:47 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Jul 2006
Posts: 4,494
Default Shortwave Radio Listener (SWL) Antennas -versus- Amateur Radio Antennas

In article ,
Dave wrote:

Telamon wrote:
In article
,
Telamon wrote:

In article ,
Dave wrote:

John Smith wrote:

However, in side-by-side comparisons on 10-6-2m antennas I have built,
comparing a 5/8 against the 1/2 (construction methods/materials and
matching components identical) ... the actual difference, in the real
world, must be less than the width of a meter needle in the readings ...
or, put simply, I no longer deal with the extra length required of the
5/8 ... your mileage may vary ...

The advantage of a physical height (antenna length) between 180 and 215
degrees (see previous post regarding the magic number being around 195
degrees) is improved take-off angle and reduced skywave-groundwave
interaction, not dramatic nearfield voltage increases.
Regarding Mr. Smith's comments above my experience and others is the
opposite. 5/8 is a much better performing antenna than a 1/2 wave for
local VHF and UHF communications. Well worth the effort to build a 5/8
wave antenna over a 1/2 wave. The 5/8 had some kind of series load coil
part way up the whip where the 1/2 wave match/compensation was done at
the base so the whip was solid. Sorry I can't more specific then that as
those experiments were many years ago.

Mr. Smith is still lost in space.


Here is an example of the 5/8 wavelength antenna I recall using in the
center of the page. The one I used was permanent mount not magnetic
though. The van roof it was installed on was the ground plane.

http://www.new-tronics.com/main/html/mobile_vhf.html

When this antenna was changed for a 1/2 wave a lot of coverage was lost.
This was before cell phones so I had to start using pay phones a lot.


The one with the center coil is a collinear. It is 2 stacked verticals
with a "delay" between.


I don't think it works that way. The coil is just a way to shorten the
total whip length. I haven't looked at the design but I would be
surprised if what you posted was true.

--
Telamon
Ventura, California
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