[Elecraft] Semi OT: vertical wire antennas

[WILLIS COOKE]

I will give you one more perspective Lew.  I run an inverted L for 80/160 which 
is suspended at the top about 60 feet high from my tower.  The wire is about 10 
feet from the tower at the ground and maybe 3 feet at the top.  I use 12 gauge 
insulated wire and at 60 feet from the ground I have a 80 meter coax trap and 
use a descending wire to tune it for 160.  I use 5 radials each 50 feet long.  
My ground is old sea bed and later rice farm so it is very 
conductive.  Sometimes there is a lot of standing water.  The antenna is fed 
withabout 200 feet of RG8X with a 6 turn decoupling coil.  The antenna will 
resonate without a tuner on 160, 80 and 10, but I used it as my only antenna for 
a few months after my other antennas were destroyed by hurricane Ike in 2008.  
It is a couple S units or more less effective than my SteppIR, but gave me a lot 
of nice contacts till I could get the beam back in operation.

I would recommend the inverted L.  The only band where 43 feet is significant is 
20 meters where it is 5/8 wavelength and will give you the biggest lobe at a 
very low angle.  The low radiation angle on all bands depends a lot on the 
ground conductivity for the first several wavelengths from the antenna.  Much 
farther away than it is practical to run radials, even for commercial 
installations.  The radials in the near field are very useful for lowering the 
ground resistance to improve the radiation efficiency, but are not so effective 
on the take off angle.  The 43 foot vertical will have a very low radiation 
resistance on 80 meters, about10 ohms, so it is difficult to tune and requires a 
very good counterpoise for good efficiency.  The L with a 40 foot or so vertical 
leg will give a similar low take off angle, but the horizontal part will 
resonate the antenna and bring the radiation resistance up to 35 or 40 ohms and 
greatly increase the band width.   Having the horizontal part horizontal is not 
at all important and sloping it downward will not hurt much at all.  If you can 
get a pully and halyard high in the tree and pull the wire up with a rope it 
makes the antenna easy to work on for tuning, etc.  Having the dead end 
suspended and with a high voltage insulator in open air will take care of the 
problem of arcing mentioned earlier.

I have seen no evidence that bare wire is more effective than insulated wire.  I 
think it depends mostly on what is available to you at low cost.  I like to lay 
the radials on the surface of the ground and hold them down with the aluminum 
tie wires sold for tying chain link. When the grass grows over the wire it will 
protect the radials from the lawnmower.  There is no advantage in trying to tune 
the radials and if your field is limited run them to the property line of the 
house or other limiting boundry or structure.  If you get tired of running 
radials, go make some contacts and see how it works.  Wait until you can't work 
some station that you really want to contact then get inspired to run a few more 
radials.  


Expect your tuning to change from day to day with the amount of rain and the 
amount of folage on the tree.  A tree may not be the ideal antenna support 
unless it is the only support available.  If it is all you have, then it is 
ideal.

Good luck and have fun.!
Willis 'Cookie' Cooke 
K5EWJ