"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!