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

[Tom Rauch]

I hope this post makes it. I've had trouble getting my mailer to send 
consistently under the right alias.

> Wouldn't there be a huge AC and DC resistance in all the wire??? That
> is what I was thinking. I believe that it takes close to 1/2
> wavelength of wire to wind a helical 1/4 wave vertical. That would 

That 1/2 wavelength requirement mostly a myth. The actual length 
of wire varies quite a bit depending on the form-factor of the helice, 
but it *always* takes more wire than properly designed lumped 
loading. Because of that, efficiency of a helical vertical will almost 
certainly be less than any lumped-loaded vertical when the ground 
losses are minimal and the lumped components are designed 
properly.

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! 

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.   

> about 2811' of wire. I suggested the typical 50' Lowfer vertical and
> got clobbered for saying so. 

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. 

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
W8JI@contesting.com