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I am currently getting my EE degree, and I'm trying to build my first antenna for a weather balloon.

I understand with a dipole, you want the feed line perpendicular to the antenna for at least l/4, but what about loop or quad antennas? It seems like people like to route the wire to the boom, then go perpendicular, then go parallel down the mast, which doesn't make sense to me.

What is the best direction to feed a loop, or more specifically a quad antenna?

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  • $\begingroup$ Unrelated to your question, but related to your application: you might want a circularly polarized system for the balloon, rather like that used for amateur satellite operation. I have worked with neither balloons nor satellites, so just take this as a suggestion to do further research. $\endgroup$
    – user2943160
    Jul 9, 2016 at 0:15
  • $\begingroup$ @user2943160 not only used by amateur satellites – you don't want all your satellite TV consumers to not only hit elevation and azimuth correctly, but also to properly align their feed for any linear polarization – especially if atmospheric effects might be randomly rotating that polarizatino! $\endgroup$
    – Marcus Müller
    Jul 9, 2016 at 14:05

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Why doesn't the configuration you described make sense to you?

The whole idea is that you want minimal interaction between current in the loop and current in the feedline. Consider the distribution of the magnetic field around the driven element in a quad antenna. Routing the feedline both radially and then along the axis of the loop are directions that are perpendicular to the field lines of the loop itself, providing zero magnetic coupling and zero induced current, which is exactly what you want.

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