[amsat-bb] Antenna design considerations

[Hans BX2ABT]

I'm slowly working towards building my own cross yagis for my home 
setup. I started learning to use MMANA-GAL in order to model the 
antennas and also looking for materials to build them. I found 8 mm 
aluminium round tubing for the elements and 3/8" square tubing for the 
boom. The cross boom is going to be 2" fiberglass, so I don't 
necessarily have to choose for foremast installation.

I decided to settle on loop fed array yagis (LFA) because they are 
directly fed with coax cable. First question: any reasons for not using 
LFAs for cross yagis?

Second question: what is the sweet spot between number of elements, beam 
width and boom length (for both 2m and 70cm antennas)? A lot of elements 
means more gain, a narrower beam width, but also a longer boom and more 
careful tracking. I haven't got any experience with working sats and I 
wonder what is better: a couple of more dB gain, or a slightly wider 
beam and a more compact antenna?

So far I modelled a 4-element and 5-element LFA for 2 meters. The 
5-element has a 1 dB gain advantage over the 4-element one, a 3 dB 
better F/B ratio, but is 2 meters in boom length, so that is quite 
substantial. Any input appreciated. Cheers. --Hans (BX2ABT)