[CQ-Contest] delta loop question 80m

[Tony Brock-Fisher]

Darrel-

I have a pair of delta loops in a phased configuration. They are very 
effective. Here are my thoughts:

-There are two ways of feeding them which result in either horizontal or 
vertical polarization. For low-angle DX work you want the vertical 
polarization (unless you can put?? the loops up higher than a half 
wavelength above ground).

-For the vertical polarization, feed the equilateral triangle full 
wavelength of wire at a point 1/4 wavelength down from the apex, near a 
corner.

-For vertical polarization, the loops need not be very high off the 
ground. The base leg of mine are only about 6-10 feet off the ground.

-An advantage is that this gives you?? a vertically polarized antenna 
that needs no ground radials! The base leg acts as a radial.

-The natural resonant impedance of a single full-wave loop is around 100 
ohms. Use a 1/4 wavelength (electrical) of 75 ohm coax to match to 50 ohms.

-You asked about bandwidth. In any given configuration, 2:1 SWR 
bandwidth is NOT large enough to cover both phone and CW. Pick one.

-Seeing as you posted this to the CQ-Contest forum, I'll give you the 
contesting answer to tuning:

 ?????? Tune the loops for phone. Then when a CW contest comes along, walk 
out to your back yard and add about a 13' stub to the middle of the base 
leg. This is easily accessible from the ground. This stub is run at 90 
degrees to the base leg and parallel to the ground. It will tune the 
loop down to the CW band. If you want to get clever it could be done 
with a vacuum relay.


Enjoy!

-Tony, K1KP