Re: A few Helical Antenna question
Chris W. wrote:
"I am unclear which polarization to use if I want 2 helical antennas to
talk to each other."
Unless you are bouncing the signals off a reflector, use the same
polarization for both.
The axial-mode helical antenna is circulaly polarized and fires along
its axis away from its ground screen. It can be either left handed or
right handed depending on which way the helix twists. It responds to
vertical, horizontal or diagonally polarized waves. It does not respond
to waves with the opposite twist to its helix. Circular polarization of
the opposite twist is rejected.
This is like machine bolt threads. A bolt can screw into a nut from
either side if it has the same itch direction, but a left hand bolt
won`t screw into a right hand nut. Circular polarization of the opposite
rotation is rejected.
Refer to any edition of "Antennas" by Kraus for the details. Kraus
invented the helical antenna after other experts said it could not work.
Best regards, Richard Harrison, KB5WZI
.
Relevant Pages
- Re: Radio Photons...
... relatively small antenna. ... Does polarization really occur and create THAT much of an effect at ... What he's describing isn't a helical antenna, it's a helically wound, ... It's operating as a monopole. ...
(sci.physics.electromag) - Re: Oddball Antenna Question?
... Roy, won't a c-pol signal remain c-pol after a low-angle terrain reflection, except that its rotation sense is reversed? ... This has been applied with good results in analog TV broadcasts using c-pol, because a c-pol receiving antenna rejects reflections of the transmitted signal -- which effectively reduces the multipath "ghosts" seen on a TV set when linearly polarized receive antennas are used. ... If you look at a higher angle where the horizontal and vertical fields are equal, that's an angle at which you'd maintain circular polarization if those same two antennas were spaced and phased for circular polarization. ...
(rec.radio.amateur.antenna) - Re: Polarization Loss?
... I'm trying to get it to have circular polarization, ... An elliptically polarized wave can be mathematically split into left hand and right hand circular components just like a linearly polarized wave can be split into orthogonal ... A right hand circularly polarized antenna will respond only to the right hand component of the elliptically polarized wave, and a left hand circularly polarized antenna will respond only to the left hand component. ...
(rec.radio.amateur.antenna) - Re: The motion of waves
... No [what makes you think atoms are circular?]. ... In which case the receiving antenna dipole should be parallel to ... your screen uses circular polarization. ...
(sci.physics) - Re: The motion of waves
... No [what makes you think atoms are circular?]. ... In which case the receiving antenna dipole should be parallel to ... your screen uses circular polarization. ...
(sci.physics.relativity) |
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