Join Date: Jun 2011
Location: Central Illinois U.S.
Wave Guide to propagate a 213 MHz signal?
Judging by online waveguide calculators much smaller and channel 13 frequencies won't propagate in a circular waveguide much smaller than 33 inches.
I tried to model a waveguide enclosed yagi for uhf (like a yagi in a garbage can.) and it proved to me how hard it is to "shield" your way into a high front to back ratio.
My frustrated attempts to get these models to report a F/B or F/R at least as good as a stagger stacked yagi made me try fully enclosing the yagi just to see if the mesh was bleeding signal (holes to large maybe?).
That is not allowed by 4nec2 (it freaked) but it proved the holes in the mesh were small enough.
It was like the garbage can (waveguide) was conducting the signal around to the front. If I remember right there was not only a poor F/B but an actual rear lobe! I abandoned the concept, though I may revisit it sometime.
Heed holl_ands warning to model it first!
my gain reports and models are here
Last edited by stampeder; 2012-05-07 at 04:03 AM.
Reason: moved into its own thread