[TowerTalk] End feeding a half-wave vetical

[Dennis O'Connor]

Jim,
My feeling is that this is much ado about very little... First, a 4 degree difference in MODELED takeoff angle on 160 is meaningless...The presence of power lines, house wiring, plumbing pipes, sewer lines, telephone wires, CATV cable, and on, and on, within the near field makes the model nothing more than a rough guide - very rough...   Everything metal out to 3 waves is going to have a major effect on your pattern...

Next the modeled TOA is only the peak point in the modeled wavefront... There is vertical spread to the TOA and I suspect that the TOA  -3dB points cover a 20 degree vertical angle, at minimum, so that would be roughly a 10 degrees to 30 degrees useable TOA ; a 4 degree change in the wavefront means nothing...  The percentage of time the arrival wavefront on 160 favors a TOA below 10 degrees is very small...

Third, the fable that an end fed half wave wire doesn't depend upon the local ground is just THAT, a fable... If you work the antenna against ground it doesn't matter a furry rodents fat pucker hole what the length of the antenna is - you are working the antenna against ground and the local ground is the major loss factor in gathering up the return currents, and the mid field ground of 1 to 10 wavelengths out has lesser importance only because the biggest bite on the signal has already been taken (not that the mid field is unimportant, it's just that we have zero control over it)...  

Now, if you feed the half wave vertical antenna as a doublet, then the local ground is shielded from having to supply return currents, to some extent but not completely, by the antenna balance, but ground at 1- 10 wavelengths out is still going to play a major role... TANSTAAFL
And, Mininec way over estimates the low angle gain of vertical antennas over ground... Take those gorgeous low angle patterns it shows with a large dose of salt...

My instinct here is that you will be far better served by sticking to quarter wave elements with smaller and cheaper balloons, and putting up a phased pair... Use Al Christman's phasing lengths for the coax... a tuner at the transmitter will allow you to move around the band with minimal losses...  And switching from broadside to endfire will allow directional gain, which will help you hear the stations answering you......

cheers  ...  denny - never at a loss for an opinion