Increasing L-Band Active Patch SNR by using it as a Feed for a Satellite Dish

Recently RTL-SDR.COM reader Bert has been experimenting with our active L-band patch antenna product. He's written in to share that he's found that using it as a feed for a satellite dish works well to improve SNR on those weaker 10500 AERO signals which Bert found that he could not decode from his location due to insufficient SNR. Our active L-band patch antenna receives signals from 1525 - 1637 MHz and can be used for signals from Inmarsat, Iridium and GPS satellites.

To use the patch as a feed Bert used a 40mm drain pipe and mounted the antenna on the end of the pipe. The drain pipe fits perfectly into the LNB holder, and once mounted the distance and polarization rotation can easily be adjusted for best SNR. He also found that adding a secondary sub-reflector about 17x17cm in size helped to boost SNR by about 3-5 dB too.

Build steps to use the Active L-band Patch with a Satellite Dish
Build steps to use the Active L-band Patch with a Satellite Dish

Bert has tested the active L-band patch as a feed on a 65cm satellite dish and a smaller 40cm dish, both with good results.

SNR Results
SNR Results
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I am using a similar setup using a discarded dish network partial disk antenna and a tripod setup beside the horn feed gizmo to hold the patch antenna. Improves the SNR to almost double what it was before with a terrific improvement showing after I tilted the Patch counterclockwise to maximize the SNR on EGC via Multipsk. Can’t beat the price for the antenna OR the Patch! Hope to do some more cool things with the freebie dish! Can anyone tell me what an ideal distance from patch to the dish at 1541 mHz? What is the formula? Maybe I can create a more permanent fixture for the patch. Thanks!


The formula i use for 1545MHz is, moving the L-band patch to the Dish to get the best overall SNR value 🙂


Tested using a 600 BPS AERO signal the patch stand alone without dish the SNR level = +/- 18
Turning the patch 360 degrees the SNR level drop to 0,0 = ZERO
Move the patch towards or from the dish, give some extra SNR level
The final result, started with SNR level = 18 and using a dish the SNR level = +/- 30 and using the sub-reflector SNR level = +/- 35

Martin Ehrenfried

OK sounds good.

The approx 17dB improvement in SNR indicates you are achieving close to the predicted gain of the dish, so the polarisation would seem to be correct.


I am not on toplevel, dish only 2 meter above ground level. Today i replace the ALU foil sub-refector for a 3mm copper plate 17×17. Now i know the exact direction and the tuning seem okee, the next step be move dish higher in the mast.

Martin Ehrenfried

If the patch antenna is circularly polarised (which I think it is) then the sense of polarisation will be swapped around by the reflection from the dish.

Incorrect or cross polarisation can result in 20dB or so signal reduction.

You may need to introduce a further sub-reflector between the dish and the feed in order to obtain the required polarisation.