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Dipole Antenna's for Jupiter Radio Astronomy
The preferable setup for observing Jupiter without having to spend hundreds of dollars for
a 3 to 5-element yagi is a dual dipole. There are two operation modes - in-phase and anti-phase.
As you can see in the charts below, those two modes have significantly different patterns.
In in-phase mode your antenna array is most sensitive to signals from the zenith.
In anti-phase the pattern of the dipoles is split into two opposite less sensitive beams.
Conclusion:
- If Jupiter is high in the sky at the time of observation use the in-phase mode.
- If Jupiter is low in the sky when radio storms occur, use the anti-phase mode.
If you live in a high latitude region, the anti-phase mode is probably the only suitable mode,
since Jupiter won't get high in the sky anyway.
East-West or North-South ?
If you have a portable RadioJove dipole system, just align the dipoles perpendicular (90 degrees) in direction
of Jupiter at the time of the predicted radio emission events.
If you use fixed standards for your RadioJove dipoles it is probably best to align the four
standards to the cardinal points and just switch the dipole wires in E-W or N-S direction.
OK, now when do we use east-west or north-south alignment ?
If Jupiter will produce radio noise
- just after rise or before set, use north-south alignment in anti-phase
mode. So the two lobes will point to east and west.
- when the planet is high in the sky, you can use east-west or north-south alignment as long as the dipoles
are in in-phase mode, so the lobe will point to the zenit.
| Dual Dipole |
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| Dual Dipole in anti-phase mode 3m above ground |
top: x ... ground plane - z ... zenit
right: top view |
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| Dual Dipole in in-phase mode 3m above ground |
top: x ... ground plane - z ... zenit
right: top view |
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Since Jupiter is quite low in the sky for northern latitiudes in the next few years, the use of a lambda/4 phasing cable is
recommended.
| Dual Dipole in in-phase mode with lambda/4 phasing cable 3m above ground |
top: x ... ground plane - z ... zenit
right: top view
Running the dipoles in anti-phase mode just mirrors the lobes on the z-axis |
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| Dual Dipole in in-phase mode with lambda/4 phasing cable 5m above ground |
top: x ... ground plane - z ... zenit
right: top view
Running the dipoles in anti-phase mode just mirrors the lobes on the z-axis |
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Single Dipole Antenna for Jupiter Radio Noise Observations
It is also possible to observer Jupiter with a single dipole, but be warned that only strong bursts will
stick out of the noise floor. While the antenna pattern of two dipoles is rather constant with height, a single dipole
dramatically changes the pattern. Since it is rather difficult to mount a dipole at heights of 5 or 7 meters above
ground, the most common operation height will be at 3 meters, like the dual dipoles above. At this height the
pattern goes straight to the zenith, albeit at a lower sensitivity than the dual dipole in-phase mode. Therefore it
is only recommended to observe with a single dipole when Jupiter is high in the sky, except you can mount it at
bigger heights.
| Single Dipole |
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| Single Dipole ~3m (lambda 1/4) above ground |
top: x ... ground plane - z ... zenit
right: top view |
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| Single Dipole ~5m (lambda 1/3) above ground |
top: x ... ground plane - z ... zenit
right: top view |
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| Single Dipole ~7m (lambda 1/2) above ground |
top: x ... ground plane - z ... zenit
right: top view |
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Antenna patterns generated with: NEC2++
Plots generated with: Xnecview
NEC manual at nec2.org
Last-Modified: Sat, 30 Apr 2005 22:42:55 GMT
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