Helical wound slim jim?
 

Anyone ever done a helical wound "Slim Jim?" Since this is a 1/2 wave
antenna with a 1/4 matching section (3/4 overall), helical winding of this
form into a 3/8 overall height (approx. 12 ft. @ 28Mhz) might be possible.
The extremely low angle of radiation (approx. 8 degrees) would make this
vertical antenna desirable...

Regards

On Sat, 26 Mar 2005 08:18:39 -0800, "John Smith"
wrote:

The extremely low angle of radiation

Hi John,

Rote learning comes through repetition:
The physical size in relation to wavelength dominates launch
characteristics, NOT electrical length.

As slim jims are generally applied to UHF/VHF use, line of sight
dominates both - that is why helically wound resistors (HT rubber
duckies) work as well as they do.

73's
Richard Clark, KB7QHC

On Sat, 26 Mar 2005 13:37:12 -0800, "John Smith"
wrote:

The rubber duckie antenna is certainly useful for some situations, however,
it is better if it stays on the walkie-talkie and we use another design for
portable or base use.

Hi John,

Given this opprobrium, what makes its cousin for 20M more suitable?
[20M is not noted for being line-of-sight either.] The principle
annoyance to erecting antennas is in matching them, beyond that, any
radiator from 0.1 to 0.625 wavelengths pretty much has the same gain
in the same direction. The difference being that some are harder to
interface to a transmitter than others.

73's
Richard Clark, KB7QHC

Hey, have you ever built any antennas? I know it is tempting to go buy a
standard issue one and ask everyone else why they bother, sometimes, I am
even tempted myself...

Regards

"Richard Clark" wrote in message
...
On Sat, 26 Mar 2005 13:37:12 -0800, "John Smith"
wrote:

The rubber duckie antenna is certainly useful for some situations,
however,
it is better if it stays on the walkie-talkie and we use another design
for
portable or base use.

Hi John,

Given this opprobrium, what makes its cousin for 20M more suitable?
[20M is not noted for being line-of-sight either.] The principle
annoyance to erecting antennas is in matching them, beyond that, any
radiator from 0.1 to 0.625 wavelengths pretty much has the same gain
in the same direction. The difference being that some are harder to
interface to a transmitter than others.

73's
Richard Clark, KB7QHC

On Sat, 26 Mar 2005 17:43:53 -0800, "John Smith"
wrote:

Hey, have you ever built any antennas?

Hi John,

Hoist your own petard, bucko. I display my call, I am among my peers
and do not post anonymously (not that your veil hasn't been penetrated
Brett).

Now, the question again:
Given this opprobrium, what makes its cousin for 20M more suitable?

73's
Richard Clark, KB7QHC

Rather, back to my original question (your ADD--attention defecit disorder
is showing), "Anyone ever done a helical wound "Slim Jim?""

Regards


"Richard Clark" wrote in message
...
On Sat, 26 Mar 2005 17:43:53 -0800, "John Smith"
wrote:

Hey, have you ever built any antennas?

Hi John,

Hoist your own petard, bucko. I display my call, I am among my peers
and do not post anonymously (not that your veil hasn't been penetrated
Brett).

Now, the question again:
Given this opprobrium, what makes its cousin for 20M more suitable?

73's
Richard Clark, KB7QHC

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:
... any radiator from 0.1 to 0.625 wavelengths pretty much
has the same gain in the same direction.
________________

This will be news to the FCC and AM broadcast stations, all of whom
understand that the ground wave from radiators of the heights you mention
above varies WIDELY, as demonstrated by empirical measurements going back
some 70 years.

For example, a 0.1 lambda radiator has about 54% of the groundwave field as
one of 0.625 wavelength, assuming a very good ground system for each (1 ohm
or so).

A matched radiator of 0.1 lambda height would need about 3-1/2X as much
input power as a 0.625 lambda matched radiator in order to generate the same
ground wave field strength over the same radio path.

RF

On Sun, 27 Mar 2005 15:29:59 -0600, "Richard Fry"
wrote:

This will be news to the FCC and AM broadcast stations


Hi OM,

Send them a singing telegram.

73's
Richard Clark, KB7QHC

.....Anyone ever done a helical wound "Slim Jim?"
yes.
Since this is a 1/2 wave
antenna with a 1/4 matching section (3/4 overall),

Why the 1/4 matching section? Seems that takes it
nearly to the full half wave length...or close
enough not to matter much...
Myself, I would probably prefer a "gamma loop"
type matching scheme, which adds no height.
To me, 16 ft tall is no more trouble than 12 ft tall
in the real world.
I've had a lightweight 32 ft self supporting radiator
up, which was no hassle at all...And the base of that
was at 36 ft on a mast. "68 ft tall total".
That was a dual band 40m GP/ 17m 5/8 GP....Full size
on both bands, relay switched.

helical winding of this form into a 3/8 overall height
(approx. 12 ft. @ 28Mhz) might be possible.
The extremely low angle of radiation (approx. 8 degrees)
would make this vertical antenna desirable... ......................

The angle of maximum radiation will vary fairly
drastically depending on height above ground.
For a "like" sized vertical, the height above
ground will have more of an effect, than any
extra electrical length. To my way of thinking,
the advantage of the extended winding should be
the largest, the closer to ground it is.
The higher above ground, approaching 1/2 wave up,
the lesser the advantage.
Note that at high heights above ground in WL,
the 1/4 wave ground plane, and the 1/2 wave
vertical have nearly the same gain for practical
purposes. "maybe .3 -.8 db difference..."
You should consider decoupling of the antenna
from the feedline also. Radiation from the line
will skew the pattern upwards off the horizon.
This will ruin even higher gain collinears.

I like my antennas full size if at all possible.
I'm a radio bully. :/ MK