bloody 'ell,,, that was slightly more than I barganned for. oh well,
every little bit helps, and ultimately confuses.
shaun.
On 4/01/2008 11:58 PM, the old scribe known as Dale Putnam was able to
impart this pearl of wisdom:
What is needed is a good effecient, multiband antenna with a general
coverage pattern.
The old saying applies... higher is better. Ok.. now that means up is
good. Low isn't. Unless you are
intent upon working everyone, including the local tv, stereo, and
sometimes even the garage door opener, within a couple hundred miles.
So.. high is good.
Now.. lets take a little bite at a time. A finite amount of power out
of a transmitter.. that doesn't change much, or shouldn't at least. So..
power out.. now it radiates best from an antenna... ok... now, it seems
to me that the best way to get the power to the antenna is with a
feedline, and the more power that can get into the antenna, the better
it will get radiated. So.. best feedline, under the conditions...
installation restrictions apply. The best feedline in the world... won't
do a lotta good if it isn't installed correctly. Shorts.. poor
connectors... bends too tight,... too close to metal... all apply.
How about asking the feedline to transfer power outside of the
parameters that it was intended? Ok.. so what is best? We ask feedline
to transfer power over a range of freq. into an antenna that is asked to
radiate with high effectiveness over the same range. If you want to do
the math... go for it. There are others that do that rather well... I'd
drather spend time playing radio, but the math still applies. So.. what
works? Everyone has their own "best". Generally speaking, the most
effective is a rather high impedance transmission or feedline. Ok...
open line.. window line.. homebrew... high price... all are
considerations.. even consideration of a single wire feeder known as a
"G" transmission line will do rather well, if the previous
considerations are taken. So.. now we have a feedline. Next the antenna.
Oh boy, here it comes, to where the rope meets leather. The antenna
needs to radiate. Really well.. and that is generally measured at the
other fellow's s meter or ears. Ok, so first, where do you want to talk?
Lets break it down. Inside a 600 mile radius or outside that circle? Now
we all want to talk all over the world... and have the strongest signal
all the time.. That just isn't going to happen. If a good signal is to
be expected within the country.. the antenna needs to be able to radiate
in such a manner as to put a signal to right "there"! Ok, we can all
figure out which antenna has what radiation pattern.... on paper.
And that is a great start. Now... how about the ground effects... the
extra bends and twists? All those can be considered, sure, but the
overriding thought may well be that the antenna needs to accept the
power being brought to it, and radiate it. Resonance, or being "cut to
frequency" works well for the imedance match to the feedline, if that is
a choice to apply. If it is a low impedance feedline.. a small change
will be noticed, because a 5 ohm change referenced to 50, isn't the
same as the same 5 ohm difference referenced to 600 ohm. Bottom line?
Ok.. here it is.. an antenna that works over the range that is needed,
and radiates with the best chosen pattern, with the highest transfer of
power from the feedline to the ether. Pick one... there are many. Many,
many pages of very good information is available to help you choose.
That is applicable.. right now. With the winter weather upon us.. now is
the time for a bit of reading, consideration... and choose. And.. if you
really want that antenna to stay up?... better consider putting it up in
the winter too.. if you put it up in the winter, it will last longer..
and pretty much work well. Some of the best antennas I've used, have
been put up in the dead of winter, and some during blizzards. Not
necessarily recommended. Which would you rather do? Build it, or maybe
read about it and choose wisely, get everything ready.. and the first
warm day... get ready... get set... then build away!
See you in the pileups, foxhunts, and most importantly... in the log,
and that's a nice QSL too!
--... ...--
Dale - WC7S in Wy
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