With the exception of a very small multi-turn loop very high off the
ground, every receive antenna is ground dependent. Worst of all IMHO is
the EWE, where the earth forms one of the elements - leading to
unpredictable results and no directivity in a desert. Beverages are
also highly ground characteristic dependent - they don't work over salt
water - but they can work well in a desert setting with radials. Two on
each end, on the ground, is typically enough - approximately 1/8
wavelength long and perpendicular to the Beverage wire. Short verticals
require decent grounds. The phased verticals I've modeled and built all
required radials to work - a minimum of four per vertical is suggested.
Short-vertical systems typically use lots of series R and some series L
to maintain a flat SWR over the frequencies of interest - some of the
series R can be in the ground rather than a resistor. I am currently
using a K9AY loop here - one ground rod is usually enough to get one
working properly - a few short radials can be helpful if the soil is
really bad. N5OT has the right idea - phase a pair and you will have a
surprisingly good antenna. A good K9AY is not as good as a decent
beverage, but they take up nearly no space and can be built for $10 and
put up in an hour.
N4GG
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|