I wanted to find a nice and easy formula to find the wavelength in air if I entered the frequency in MHz so I did the math:
light = 30000000000cps / 2.54cpi = 11811 - the number I was looking for.
11811/27.185 (center of band) = 434.5"
434.5 x .64 = 278"
434.5 x .625 = 271.5"
If the Imax comes in at 270.5" then it is 1 inch short for a .625 (5/8) which I bet is made up for by the fiberglass medium slowing the velocity factor a bit.
I believe the imax is a 5/8 not a .64
Another anecdotal comparison was done last weekend. I helped erect a Sirio Gainmaster in place of a good working Imax on top of a 36' telescoping mast from the ground up, in a backyard, 80' from the house, and using dacron guy line, no metal.
Coax was LMR-400.
The Gainmaster was actually lower in transmit signal strength to a couple stations about 35 miles away.
I wonder if the lower angle of the Gainmaster didn't get his signal up and over local hills as well as did the Imax with it's higher toa.
Maybe the Gainmaster doesn't like being right at one wavelength above ground
Basically they performed almost exactly the same nearby, a few stations in the distance saw improvement and a few others in a different direction saw a decline.
Overall his receive is improved but only a little bit and not in all directions.
Surprisingly, for his
application, the Imax might be the better performer.