Thanks for the info. An A&P & experienced avionic installation centre will be doing the install and xpdr test so it will be their call at the end. I am just trying to understand why there are varying ground plane recommendations between the trig manual, RAMI antenna mfr and what Scheichler typically recommends. Mpa-Thank you for the explanation. I know understand a bit better the trade-offs in the ground plane sizes. I saw the L-2 antenna. Seems nice.