In my previous post I elaborated somewhat on Outernet being merely
a ‘nerdy’ technological project. Adam 9A4QV designed a L-band patch antenna
a while ago. Cutting two diagonal opposite corners yields circular polarization.

The two diagonals differ 90° in phase, the longer diagonal +45°
(so the antenna is inductive), the shorter -45° (so the antenna is capacitive).

+45 – (-45) = +90°, exactly what is needed for circular polarization (CP).
InmarSat L-band transmits with Right Handed Circular Polarization (RHCP).

This posting attempts to illustrate an utter simple patch antenna built
(in 20 minutes).

Dimensions of 9A4QV’s L-band patch antenna are:

Reflector Size: 170 x 170 mm
Patch Size: 98 x 98 mm
Corner Trim: 21 mm from top right and bottom left corners
Coax Connection (Probe): 25 mm from bottom edge
Height of patch from reflector: 7 mm

Step 1. My reflector is made from 1mm thick aluminium sheet.
The patch is made from 0.5mm thick double sided FR4 PCB. I had some spacers and
cut one with a saw to 7 mm length. Anything else will do, as long as reflector and patch
are ~7 mm separated and electrically connected (the impedance Z = 0 Ω in the middle!).

I chose a N-type chassis connector instead of SMA, but your mileage may vary.
See picture below (click on it to enlarge in a new tab).


Step 2. Create correct dimensions with a caliper, drill holes accordingly . . .
and . . . ready ! See picture below (click on it to enlarge in a new tab)
Note: Fingerprints on the patch element are not mine ; -)

Side view depicted below (click on it to enlarge in a new tab).

Finally, one picture to summarize all (again, click on it to enlarge in a new tab : -)
Yes, I know I made a typo, it has to be corneRs instead of cornes ; -(