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UoSAT antenna pattern?


Can anyone do better than this?

I am trying to model the radiation pattern from the UoSAT (eg UO-22, KO-23,
KO-25 etc) satellites on the 70cm downlink.  Unless anyone can do better,
I'm going to use;

Radiation Intensity F(theta) = ( sin(theta) ) ^3

i.e the sin of theta all raised to the third power, where theta is the angle
of radiation away from the z-axis.

This equation gives a null straight through the z-axis (the radiating
element being along that axis), and a maximum at 90 degrees, which means a
maximum straight toward the horizon (assuming the satellite always has it's
z-axis pointing towards the centre of the earth, which it does).

The -3dB beamwidth works out to about 54 degrees, which is about right for a
halfwave dipole.

Also, in the program that uses this, I am proposing to put a 12dB ceiling on
the loss of signal straight along the z-axis, as this reflects the worst
case loss I have seen when looking straight up into the -z axis of the
satellite on direct overhead passes...  any comments on whether 12dB is a
suitable figure?

73 Chris VK6KCH

 |  Chris Hill            email : vk6kch@amsat.org |
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