Antenna Question
 

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

Any special considerations?

How can I predict the band width?

Roger Gt wrote:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

Any special considerations?

Mechanincal considerations more probably a problem than
electrical considerations.


How can I predict the band width?

Numerology gives about as good a result as others...
'Doc

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

How long?

Any special considerations?

How long you are to make your dipole, and what frequency do you intend to
operate?

How can I predict the band width?

In general wider and thicker produce wider bandwidth. Short dipoles or long
ones in terms of wavelength may have reduced bandwidth because of limitations
of matching devices.
As you know, bandwidth does not mean a good antenna. A resistor can have a
huge bandwidth, but radiate very little.
73 Gary N4AST

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

Any special considerations?

How can I predict the band width?

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

None. And no need to predict bandwidth. It will be more than wide enough.

"JGBOYLES" wrote in message
...
Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

How long?

Any special considerations?

How long you are to make your dipole, and what frequency do you intend to
operate?

How can I predict the band width?

In general wider and thicker produce wider bandwidth. Short dipoles or
long
ones in terms of wavelength may have reduced bandwidth because of
limitations
of matching devices.
As you know, bandwidth does not mean a good antenna. A resistor can
have a
huge bandwidth, but radiate very little.
73 Gary N4AST

40 meters is the primary, there is enough space to do a full length dipole
with folded ends (about 12 to 15 feet. If it works I wanted to put a 20
meter dipole in the other side about three feet higher up the rafters.

I am familiar with wire antennas, and matching, but have never tried using
sheet stock as an antenna below 10 meters, and that was is an apartment.

Reg Edwards wrote:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.

Any special considerations?

How can I predict the band width?

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

None. And no need to predict bandwidth. It will be more than wide enough.

None? Unless this is an attic antenna, wind will be a big consideration,
and possibly noise (acoustic) as well. I don't know all the laws of static induction
into
an antenna, but it seems to me that you might also want to watch for arcing
in connectors etc.

Irv VE6BP
--
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Beating it with diet and exercise!
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Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

"Irv Finkleman" wrote in message
...
Reg Edwards wrote:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.
Any special considerations?
How can I predict the band width?
========================
None. And no need to predict bandwidth. It will be more than wide
enough.

None? Unless this is an attic antenna, wind will be a big consideration,
and possibly noise (acoustic) as well. I don't know all the laws of
static induction
into
an antenna, but it seems to me that you might also want to watch for
arcing
in connectors etc.

Irv VE6BP

IN the attic... Of course, and there will be no connectors.
Direct termination to the Sheet via lugs.
Insulated by plastic dowels, about 4 inches (~100mm) long.

I will also install two feet above the House wiring, ducts etc.

So I'll let you know how it works. In a while.

Thanks, Every one!

On Wed, 14 Jan 2004 04:08:06 GMT, "Roger Gt"
wrote:


"Irv Finkleman" wrote in message
...
Reg Edwards wrote:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.
Any special considerations?
How can I predict the band width?
========================
None. And no need to predict bandwidth. It will be more than wide
enough.

None? Unless this is an attic antenna, wind will be a big consideration,
and possibly noise (acoustic) as well. I don't know all the laws of
static induction
into
an antenna, but it seems to me that you might also want to watch for
arcing
in connectors etc.

Irv VE6BP

IN the attic... Of course, and there will be no connectors.
Direct termination to the Sheet via lugs.
Insulated by plastic dowels, about 4 inches (~100mm) long.

I will also install two feet above the House wiring, ducts etc.

So I'll let you know how it works. In a while.

Thanks, Every one!


Just in case the concern about a fire hazard from arcing or
corona discharge is a possiblity, it might not be a bad idea to blow a
few bucks on a smoke detector up there.

On Tue, 13 Jan 2004 22:51:35 GMT, Roger Gt hath writ:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.
Any special considerations?
How can I predict the band width?

At 1296 MHz?

On Wed, 14 Jan 2004 11:28:01 GMT, wrote:

Just in case the concern about a fire hazard from arcing or
corona discharge is a possiblity, it might not be a bad idea to blow a
few bucks on a smoke detector up there.

and as a benefit, if you work CW, you might get sidetone.

73's
Richard Clark, KB7QHC

"Lou DeChris" wrote in message
...
On Tue, 13 Jan 2004 22:51:35 GMT, Roger Gt hath writ:

Aluminum strip, 10 inches wide and .006 inches thick as a dipole.
Any special considerations?
How can I predict the band width?

At 1296 MHz?

My tome is brief, scarcely a page in the sands of time.

It would make a lot of Bow-ties and reflectors, but I was tying to make an
indoor antenna for 40 / 20 Meters.

While the average wind is only 10 mph. Seasonally the winds get to 35 mph
with maximum gusts to over 85 mph. My 10 / 15 wire antenna's are the most
used, and require frequent maintaince. The indoor antenna's (also #17
Aluminum electric fence wire) are always available. I wanted to add more
bands, and have an entire roll of this sheet stock which is just taking up
shelf space.

In reply to other suggestions, all fasteners are Aluminum, and the
insulators are PVC. The support lines are 40lb monofilament fishing line,
and the tensioners are Screen door springs at the extreme support points.
Coax feeds are all RG8U. I bought a roll! 2 meters and up are covered by
a Radio Shack discone.

160 and 80 Meters are (very) spiral wound on 20 foot of 4 inch drain pipe
forms. ( works but NOT real good IMHO)

Roger wrote:
"Any special considerations?"

A dipole in the HF range using aluminum strip 10 inches wide and .006
inches thick has a small length to width ratio and that`s good for
bandwidth. The width is sufficient for good surface conduction and that
is good for efficiency.

Most data are for copper but aluminum is only 1.6X as resistive as
copper, so there is not much electrical difference in performance. .006
inch is sufficiently thick to prevent significant RF penetrationat at
HF, and if RF did penetrate it would not be detrimental.

Bandwidth of an antenna may be determined by acceptable directional
character or it may be determined by acceptable drivepoint impedance.

Ed Laport in "Radio Antenna Engineering" has made a "Free-Space Dipole
Characteristics" table for bandwidth as limited to the region where the
antenna`s reactance is less than its radiation resistance at resonance.

At 10 MHz, a dipole made of Roger`s aluminum strip would have an
equivalent length over diameter (L/D) of about 59.

From Laport`s Fig. 3.1 on page 248, a dipole of L/D of 200 would be
resonant at an electrical length of 168.3-degrees. Its 3 dB bandwidth is
11.2% and its 1 dB bandwidth is 5.6%. The aluminum strip dipole at 10
MHz has a smaller effective L/D and produces a wider bandwidth than any
shown in Laport`s table.

Consult "Radio Antenna Engineering" for more information.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Roger wrote:
"Any special considerations?"

A dipole in the HF range using aluminum strip 10 inches wide and .006
inches thick has a small length to width ratio and that`s good for
bandwidth. The width is sufficient for good surface conduction and that
is good for efficiency.

Most data are for copper but aluminum is only 1.6X as resistive as
copper, so there is not much electrical difference in performance. .006
inch is sufficiently thick to prevent significant RF penetrationat at
HF, and if RF did penetrate it would not be detrimental.

Bandwidth of an antenna may be determined by acceptable directional
character or it may be determined by acceptable drivepoint impedance.

Ed Laport in "Radio Antenna Engineering" has made a "Free-Space Dipole
Characteristics" table for bandwidth as limited to the region where the
antenna`s reactance is less than its radiation resistance at resonance.

At 10 MHz, a dipole made of Roger`s aluminum strip would have an
equivalent length over diameter (L/D) of about 59.

From Laport`s Fig. 3.1 on page 248, a dipole of L/D of 200 would be
resonant at an electrical length of 168.3-degrees. Its 3 dB bandwidth is
11.2% and its 1 dB bandwidth is 5.6%. The aluminum strip dipole at 10
MHz has a smaller effective L/D and produces a wider bandwidth than any
shown in Laport`s table.

Consult "Radio Antenna Engineering" for more information.

Best regards, Richard Harrison, KB5WZI


Thanks, that is the kind of reference and information I was seeking. I'll
get the book too!