Russell Hill wrote:
> Welcome to Geekland!
> Put up the biggest antenna you can afford, just as high as you can get it.
------------------
Have to agree with the "biggest" part of Russell's message, but that
"high" bit is one of the worst things you can do. Unless, of course,
you're speaking of stacked yagis.
You must take into consideration that a very good wide spaced single
band yagi will begin to form lobes at higher angles once it is raised
above 1/2 wave above true ground.
Once you get the antenna very high, you will end up with about 5 or 6
lobes. Of course, the bottom one will be at a very good angle, around
10 degrees. But one must take into consideration that every lobe
radiates power. And while you may generate a full KW into the total
antenna, you can well wind up with only 300-400 watts into that low
lobe. Add in the back lobes, and power loss is significant.
It's hard to make a good compromise, but a little time spent computing
the "footprint"
of a lobe based on reflection at daytime or night levels of the
ionosphere will pay off nicely. And for some contests, such as the
SS,the very last thing you want is a 10 degree lobe. Not much in the
middle of the Atlantic when the first reflection occurs.
I once had a 80 meter triangle loop which had a take off of about 7
degrees. Antenna could absolutely kill on very long haul, but was
worthless for anything closer than the middle east.
73
Ed
---------------------------------------------------------------
The world's top contesters battle it out in Finland!
THE OFFICIAL FILM of WRTC 2002 now on professional DVD and VHS!
http://home1.pacific.net.sg/~jamesb/
---------------------------------------------------------------
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|