I've been receiving satellite signals in the L-band (~1.7GHz), recently.

These signals are RHCP. So far, I've been using a DIY helical antenna in axial mode, and a patch antenna with cropped or clipped corners.

My favorite tool to calculate the latter, is btw. this: http://kempbros.github.io/antennas/Patch_Antenna_Generator/

Anyway, when a signal is RHCP, I need an RHCP antenna to receive it, that's quite logical, and I can visualise in my head, how the propagation works, etc.

But now I'd like to use a dish as a reflector, but as I imagine things, the reflector works like a mirror, and will change the polarity of the circular polarized signal. So to receive a RHCP signal with a parabolic dish antenna (receiving element pointed at the dish, similar to how the LNB is mounted on a Ku-band antenna for satellite TV), I'd need a LHCP antenna in the focal point of the dish.

At least that's how I understand it, but like I said, at this point I'm super confused.

up vote 9 down vote accepted

A parabolic reflector reverses the sense of circular polarization. so your feed must have the opposite sense or "handedness" to the incoming signal to avoid significant polarization loss.

A way to avoid rebuilding an existing RHCP antenna would be to use a second, planar, reflector which would re-invert the polarization's handedness. If the satellite is close to the horizon, for example, the reflector could be tower mounted at a near 45 degree angle to beam the signal to a ground mounted dish, which may also be more convenient than a tower mounted dish.

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