http://elecraft.85.s1.nabble.com/dipole-antenna-efficiency-tp458071p458107.html
bloody 'ell,,, that was slightly more than I barganned for. oh well,
> 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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