For horizontal polarization, picture a rectangular driven element with
the narrow end down. It is about .1274 wavelengths at the bottom and
top. It is about .40266 wavelengths tall. It is fed at the center of the
bottom wire.

Put a reflector behind it. The reflector is .2643 wavelengths at the
bottom and top. It is .305 wavelengths high.

The geometric center of the reflector aligns with the geometric center
of the driven element.

The feed impedance is about 48+j0 ohms but can be adjusted based on
other requirements, if necessary. The max gain is 12.9dBi when about 3
wavelengths above earth. I can reduce the wavelengths above earth with
an attendant increase in max radiation angle, but that's another study.

I might use this one on 434MHz for a 1000ft link. I don't really need
the gain so much as the matching and the desire to minimize radiation in
useless directions as well as max signal at a low angle.

Thoughts?

John S wrote:
For horizontal polarization, picture a rectangular driven element with
the narrow end down. It is about .1274 wavelengths at the bottom and
top. It is about .40266 wavelengths tall. It is fed at the center of the
bottom wire.

Put a reflector behind it. The reflector is .2643 wavelengths at the
bottom and top. It is .305 wavelengths high.

The geometric center of the reflector aligns with the geometric center
of the driven element.

The feed impedance is about 48+j0 ohms but can be adjusted based on
other requirements, if necessary. The max gain is 12.9dBi when about 3
wavelengths above earth. I can reduce the wavelengths above earth with
an attendant increase in max radiation angle, but that's another study.

I might use this one on 434MHz for a 1000ft link. I don't really need
the gain so much as the matching and the desire to minimize radiation in
useless directions as well as max signal at a low angle.

Thoughts?

That is about 7 feet at 434 MHz; hope there is nothing in the way.



--
Jim Pennino

On 11/26/2014 12:28 PM, wrote:
John S wrote:
For horizontal polarization, picture a rectangular driven element with
the narrow end down. It is about .1274 wavelengths at the bottom and
top. It is about .40266 wavelengths tall. It is fed at the center of the
bottom wire.

Put a reflector behind it. The reflector is .2643 wavelengths at the
bottom and top. It is .305 wavelengths high.

The geometric center of the reflector aligns with the geometric center
of the driven element.

The feed impedance is about 48+j0 ohms but can be adjusted based on
other requirements, if necessary. The max gain is 12.9dBi when about 3
wavelengths above earth. I can reduce the wavelengths above earth with
an attendant increase in max radiation angle, but that's another study.

I might use this one on 434MHz for a 1000ft link. I don't really need
the gain so much as the matching and the desire to minimize radiation in
useless directions as well as max signal at a low angle.

Thoughts?

That is about 7 feet at 434 MHz; hope there is nothing in the way.

The target application is for a remote water level sensor in the
countryside. No problem with height there.

"John S" wrote in message
...
Thoughts?

That is about 7 feet at 434 MHz; hope there is nothing in the way.

The target application is for a remote water level sensor in the
countryside. No problem with height there.

HI
At UHF total and permanent clearance of the Fresnel zone
is the rule for reliable results.
Directional antennas at both sides helps a lot too but higher is always
better
At such low height rain ,snow and even cutting the grass will produce
variations.

On 11/27/2014 9:06 AM, bilou wrote:
"John S" wrote in message
...
Thoughts?

That is about 7 feet at 434 MHz; hope there is nothing in the way.

The target application is for a remote water level sensor in the
countryside. No problem with height there.

HI
At UHF total and permanent clearance of the Fresnel zone
is the rule for reliable results.
Directional antennas at both sides helps a lot too but higher is always
better
At such low height rain ,snow and even cutting the grass will produce
variations.

You don't know the particulars.

The angle of maximum radiation is about 6 degrees. At 1000 feet, I will
need a height of about 104 feet to be in the lowest (max radiation)
area. The remote site is about 80 feet below my receiver (a flood plane)
and the receiver antenna is about 20 feet above the point of reception.
It is why I chose the height of the antenna. Of course, this all remains
to be tested.