What is the Beam Width of My Moxon Yagi?

I had homebrewed a Moxon Yagi some time back and have been using it for LEO Amateur Radio Satellite operations for the past few months. Being an antenna with only a single Moxon Rectangle for VHF, I knew the beam width will be rather high. When I checked the M1GEO/G8OCV page, the design which I had used, there were plots of radiation pattern for both VHF and UHF as well as the resonant frequencies. Resonant frequency at VHF was 145.825 MHz and that at UHF around 437.25 MHz. Both were quite suitable to work Amateur Radio on International Space Station. From radiation pattern chart, I could gather the approximate beam width on VHF at 140 degrees and that at UHF around 80 degrees. Lower beam width at UHF was expected as it had 5 elements for UHF as a Yagi. Gain was mentioned as 3.95 dB at VHF and 8.06 dB at UHF.

Today night I decided to check how it worked practically for me on a 15 degree elevation pass of Space Station. I pointed my antenna towards the beginning of the pass and tried listening in on stations on the Space Station pass. I could hear couple of local stations well when the Space Station was almost 90 degrees away from the direction in which I had pointed the antenna. I had noted similar reception earlier also. So that tallies fairly well with the estimated beam width of the antenna. Higher beam width helps me to receive stations for a longer period during each pass. On the down side, I am unable to work satellites with weaker power output because of the lower gain. But that is a trade off between gain and beam width for a fixed elevation azimuth antenna.