Dale Parfitt wrote:

PS I would like to build 2 of these one is for 2.4ghz wireless network


and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz
version will likely never see more than 100 mW but could see as much as 1
watt. The 432 mhz version could see as much as 1000 watts, but if I did
that it would be to an array of 4 of them so I guess each one would only
see 250 watts?

--
Chris W



EME on 432 is linearly polarized (although switching polarities to make up
for Faraday rotation can be advantageous) - you'll be throwing away a huge
3dB, have higher sidelobes than a well designed Yagi (nullifying the low sky
temp advantage of deep space) and less gain per boom length than a good
Yagi- all in all, a dismal choice for EME.

Dale W4OP




The calculation in the ARRL Antenna book say that a 12 foot boom with a
circumference of 1.33 wavelengths will give me a 19.9 dbi gain this
should make up for the 3 db loss I think. I haven't seen a yagi that
gives that much gain in with a 12 foot boom. The book also says that
the side lobe problem can be significantly reduced by creating an array
of 4 helical antennas. That should up the gain to 25.9 db. That's
pretty good for EME isn't it? Take it to 16 and you get over 30 db
gain. And the only need to be spaced at 1.5 wavelengths, that's only
3.4 feet.

--
Chris W

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