Brian Reay wrote:
The explanation is a fairly standard one, although Walt does express it
well. If Walt is the originator of the idea I suspect he has a many more
turns on the coil than he is admitting ;-)

From "Radio Handbook" by Bill Orr, 20th edition, copyright 1975,
section/page 27.9: "The feedpoint impedance of a ground plane may
be raised to about 50 ohms by drooping the radials down at a 45
degree angle." Anyone got an earlier edition?
--
73, Cecil http://www.qsl.net/w5dxp


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Brian Reay wrote:

"Cecil Moore" wrote:
From "Radio Handbook" by Bill Orr, 20th edition, copyright 1975,
section/page 27.9: "The feedpoint impedance of a ground plane may
be raised to about 50 ohms by drooping the radials down at a 45
degree angle." Anyone got an earlier edition?

Not of that book, but similar wording in ARRL's 1972 "VHF Manual". I found
it, but not the book I was looking for.

You're right, page 179: "Another matching trick with the ground-plane
is to droop the radials downward, adjusting their angle below the
horizontal until the antenna feed impedance becomes 52 ohms. This
usually occurs at about a 45-degree angle."
--
73, Cecil http://www.qsl.net/w5dxp


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Radials function as a counterpoise, and, when there are enough radials, a
ground plane.

If you wish to attenuate ground losses, then it is best to make the most of the
surface by using as many radials as possible. The first dozen+ are the most
critical in reducing ground losses. Even a dozen or so helps substantially or
over 3, for example. Several dozen reduces ground losses substantially.

Elevating radials always helps.

73,
Chip N1IR

"Fractenna" wrote

Radials function as a counterpoise, and, when there are enough radials, a
ground plane.

If you wish to attenuate ground losses, then it is best to make the most
of the
surface by using as many radials as possible. The first dozen+ are the
most
critical in reducing ground losses. Even a dozen or so helps substantially
or
over 3, for example. Several dozen reduces ground losses substantially.

Elevating radials always helps.

73,
Chip N1IR


Welcome back to the group, Chip! Where have you been?

Jack Painter
Virginia Beach, Virginia

On 11 Jan 2005 22:26:54 GMT, (Fractenna) wrote:

Radials function as a counterpoise, and, when there are enough radials, a
ground plane.

If you wish to attenuate ground losses, then it is best to make the most of the
surface by using as many radials as possible. The first dozen+ are the most
critical in reducing ground losses. Even a dozen or so helps substantially or
over 3, for example. Several dozen reduces ground losses substantially.

Elevating radials always helps.

73,
Chip N1IR

Well, Chip, as the inventor (Dr. George H. Brown) said, two radials
are sufficient for a ground plane, but the RCA sales dept thought they
would sell better with four. But a ground plane antenna suffers no
ground losses, so using as many as possible only applies to radials on
or in the ground.

Walt, W2DU

"Brian Reay" wrote:

:
: I'm sure it is much older than 15 years- it was around when I did my RAE
: (more than 15 years !). I'm pretty sure it is the the old Admiralty
: Handbook, but I can't lay my hands on mine. You see a similar effect when
: making a dipole into and inverted V.
:
: It is certainly taught on at least one Advance RCE course ;-)


anyone else notice how Brian comes to the aid of
his faultering/slipping anonymous comrade ?

On Wed, 12 Jan 2005 14:41:33 -0000, "Airy R.Bean"
wrote:

Discussed in the "Antenna Manual", by Woodrow Smith,
pub "Editors and Engineers Ltd " dated 1948.

He refers to the "Brown Ground Plane Antenna" and separately
to the "Drooping Ground Plane Antenna"

But does he refer to the 'drooping' as an impedance-matching device?

If not, what reason does he give for the technique?

wrote:

: On Wed, 12 Jan 2005 14:41:33 -0000, "Airy R.Bean"
: wrote:
:
: Discussed in the "Antenna Manual", by Woodrow Smith,
: pub "Editors and Engineers Ltd " dated 1948.
:
: He refers to the "Brown Ground Plane Antenna" and separately
: to the "Drooping Ground Plane Antenna"
:
: But does he refer to the 'drooping' as an impedance-matching device?
:
: If not, what reason does he give for the technique?

capacitance is prop to gap between plates.

On Thu, 13 Jan 2005 20:05:24 GMT,
(ZZZPK)
wrote:

wrote:

: On Wed, 12 Jan 2005 14:41:33 -0000, "Airy R.Bean"
: wrote:
:
: Discussed in the "Antenna Manual", by Woodrow Smith,
: pub "Editors and Engineers Ltd " dated 1948.
:
: He refers to the "Brown Ground Plane Antenna" and separately
: to the "Drooping Ground Plane Antenna"
:
: But does he refer to the 'drooping' as an impedance-matching device?
:
: If not, what reason does he give for the technique?

capacitance is prop to gap between plates.


I think you meant that it's inversely proportional to the gap between
the plates.

Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

W9DMK (Robert Lay) wrote:

(ZZZPK)
wrote:
capacitance is prop to gap between plates.

I think you meant that it's inversely proportional to the gap between
the plates.

I've made the same mistake - said "capacitance" when I really
meant "capacitive reactance".
--
73, Cecil http://www.qsl.net/w5dxp


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