[Lowfer] FW: 600MRG> Helically wound vertical on a city lot>NO WAY!!!

[Ed Phillips]

> By the way, optimum form factor of a inductor is NOT 2.5 to one or
> any other number. It typically ranges from about 1:1 to 4:1,
> depending on the required reactance at the operating frequency.
> High reactances require longer form factors, because the shunting
> capacitance must be minimized. Any capacitance across a high
> reactance inductor greatly increases circulating currents from end-
> to-end capacitance, and that increases losses while bandwidth is
> actually reduced!

	The optimum shape for minimum losses/maximum Q is so broad that it's
hardly worth bothering about.  I like "square" (1 x 1) coils just
because they are a convenient shape to wind, but usually just use
whatever form and wire I have.  IF you had a perfect ground then going
for the absolute maximum Q in the loading coil would be worth the
effort, and that's the way all of the "old time" LF antennas were
designed.  As much attention spent on the ground/counterpoise as on the
antenna part, although of course the suspension of the wires and the
cost of the towers was much larger than the cost of building the ground. 

> Efficiency might be more than a base-loaded vertical, especially if
> the ground system is poor. I sure think it would be less than a
> good center-or-higher loaded vertical, because the center loaded (or
> higher) vertical would have higher radiation resistance than the
> helical antenna.
> 
	The problem with moving the loading up the mast is that the required
inductance gets higher and (at 180 kHz) it's much harder to build and
mount a good high-Q coil way up in the air.  I know of a few local
attempts at doing that, particularly a lot of work done by K6QAY about
20 years ago, and it turned out not to be worth all of the bother.  Bob
built some really beautiful variometers which he mounted between the top
of his mast and the toploading cage, but didn't really put out a much
better signal.  Same setup with appropriate inductor did help quite a
bit on 160 meters, but that's at 10 times the frequency.
> 
> Many or most of the general population like to use cut-and-try
> rather than science and reasoning in antennas. Much of the time
> there is nothing wrong with that, because we often learn something
> we don't know from enough trial and error.

	True if, and only if, we're smart enough to understand what happened
and learn from it.  Not all are, hence some of the "magic" antenna
designs you see floating around.
 
> The only sad thing is when someone claims science or physics
> really doesn't quite understand how lumped components,
> resistance, reactance and radiators work. When that argument
> surfaces, it is time to bail out.
> 73, Tom W8JI

	Amen to that, including knowing when to bail.  When the nuts take over
the asylum it's time to move on.  I'd add to that the accusation that
"you don't have an open mind and aren't willing to welcome new and
brilliant ideas"!

Ed