VA2GU
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Re:40M antenna survey - 2011/03/10 22:50
CGQ
BEST ANT PR 40M
BEST ANT. FOR LIMITED AND UNLIMITED SPACE AT LOW HEIGHTS and for
80m as well as for 40m is a pair of phased dipoles.
Space required on 40m is half wave long for each dp, spaced 33 feet.
Yes 30' high is plenty high, because the phasing will take off that high
worthless angle to put your precious watts in the low angle lobe. This
gives you great front to rear as well if you care for it.
And phasing for 2 dipoles is no black magic. You just add a quarter wave
piece of coax to the element you want to be the front of your array. You
then switch it to reverse direction. Be aware that that coax may not be 90
degrees long, due to the Z of your dipoles. It may end up being 115 or
120 degrees long for optimum results. You will hear the diff. in the
receive performance, even if you only listen to the noise!
For 40m, you can even put three phased dipoles in a square of 66feet
wide by 66' long (33' between each dp), for added gain and f/r. Phasing is
a little bit more fun here, but again no black magic.
As for verticals for lower angles AND NILL NOISE (YES VERT. POLAR. WITH
NO NOISE), you need 2 supports spaced 45' and about 35 feet high.
You then hang a CVA (sort of a shorted bottom bobtail to give you the
50ohms Z rather than the 2000 ohms of the bobtail). AND it could care
less about the ground under; so no radials needed: it wont help. Model it
you see.
BUT if you space those 30' supports at 95 feet, you can a real grass
burner made up of 3 verticals, shorted across their tops AND bottoms and
beating the four square (with its four supports and how many radials?).
Again 50 ohms Z and feed anywhere on ANY of the verticals. 50 ohms
anywhere. And because they are a dc short, you get nil noise and no static
build up. They are even quieter than a beverage; believe me i've done it!
Then the penultimate, add such an array 33 feet behind the first one and
get BETTER GAIN than a real 6 square with its six support and 120?
radials.
Again CVA needs no radials and could care less about the state of the
ground under.
To sum up, i'd use 2 CVA (six verticals) on any band (90'WX33'LX35'H on
40m).
roy, va2gu[size=4][/size]
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