2M horizontal polarized mobile antenna?
 

Any ideas for an omni directional antenna for 144.200 that could be
mounted above the topper of my pickup? Something like a halo/squalo?

Scott
N0EDV

Why not a Halo!

acepilot wrote:

Any ideas for an omni directional antenna for 144.200 that could be
mounted above the topper of my pickup? Something like a halo/squalo?

Scott
N0EDV

Dale,
I'm not disputing your claims, but what does "slightly
more integrated gain", mean?
'Doc

Oops, my fault! I should have elaborated just a bit more. I'm looking
for something to build on the cheap because it will be basically a
one-time use. A halo would be fine if I can build one. I have plans
for something similar from the RSGB VHF/UHF Manual, but it doesn't show
the feedpoint matching detail, so I'm not sure how to match it to 50
Ohms...something made of copper pipe or some 3/16" (I have a source)
steel wire that is copper clad (power pole ground wire) that could
handle 70 MPH.

Scott
N0EDV

Dave Shrader wrote:
Why not a Halo!

acepilot wrote:

Any ideas for an omni directional antenna for 144.200 that could be
mounted above the topper of my pickup? Something like a halo/squalo?

Scott
N0EDV

"'Doc" wrote in message ...


Dale,
I'm not disputing your claims, but what does "slightly
more integrated gain", mean?
'Doc

We sent all the commercially available omnis to the Motorola anechoic
chamber in Boynton Beach FL. Traditional shortened dipole type omnis (
loop/haloes) showed an elliptical AZ pattern- about 3dB "out of omni" as I
recall. If one only measured the gain off the front or rear this style
antenna had more gain than the isosceles triangle style omni- whose
electrical length is longer than a half wave. However if one looked at the
gain every 10 degrees or so of azimuth and averaged this over the full 360
degrees, the triangle style had more gain- again, from memory, it was about
0.5 dB better- not a lot, but in the right direction. Modeling confirms both
the pattern and gain.

Dale W4OP

Scott, N0EDV wrote:
"I have plans for something similar from the RSGB VHF/UHF Manual, but it
doesn`t show the feedpoint matching in detail, so I`m not sure how to
match it to 50 Ohms."

Mine is the 3rd edition with Halo Aerials starting on page 7.29. Make
the shorting bar (A) adjustable in distance from the PL259, instead of
brazed to the brass tubes. Adjust for minimum reflected power in your
50-ohm coax.

Best regards, Richard Harrison, KB5WZI

Dale, W4OP wrote:
"We sent all the commercially available omnis to the Motorola anechoic
chamber in Boynton Beach, FL."

My first concern would be horizontal polarization, not eccentricity in
azimuth. In a mobile station, I first would want to work other local
mobiles.

Best regards, Richard Harrison, KB5WZI

My book is the 4th edition, so I'm not sure which antenna you have. Is
its circumference listed as lambda/2 or 0.7536 lambda? If it's the one
I suspect (0.7536 lambda) where do you feed it and where does the
shorting bar that you mention go?

Thanks!

Scott
N0EDV

Richard Harrison wrote:
Scott, N0EDV wrote:
"I have plans for something similar from the RSGB VHF/UHF Manual, but it
doesn`t show the feedpoint matching in detail, so I`m not sure how to
match it to 50 Ohms."

Mine is the 3rd edition with Halo Aerials starting on page 7.29. Make
the shorting bar (A) adjustable in distance from the PL259, instead of
brazed to the brass tubes. Adjust for minimum reflected power in your
50-ohm coax.

Best regards, Richard Harrison, KB5WZI

Scott, N0EDV wrote:
"Here it is---."

The 1/2-wave circumference halo at the top, is fed at points A-A and
uses a typical gamma match.

The one-wavelength loop doesn`t use a gamma match. It is in effect a
quad loop antenna. It really shouldn`t need much impedance adjustment to
match 50 or 70 ohms. In free-space, a full-wave loop has a feedpoint
impedance of near 45 ohms. That may not have satisfied the designers. I
don`t know the impedance of the 0.2 wavelength stub shown as a
connection at points A-A for the feedline. With the line spacing shown,
it probably has an intermediate impedance between that of the loop and
the intended feedline. No gamma match and shorting bar are involved.

The one-wavelength loop is not really omnidirectional. It has a 1-dB
gain perpendicular to the plane of the loop in free-space.

Best Regards, Richard Harrison, KB5WZI