At PJ2T we built them for phone and we add length to make them work on
CW. In that installation we have ceramic knife switches installed as
insulators that we just go out in the yard and change over. Problem
solved. If it was me at N5OT I would cut it for CW but keep a matching
network in the circuit. Problem solved. I would be loud and make a lot
of contacts.
73 - Mark N5OT
On 7/29/2019 7:47 AM, Tony Brock-Fisher via CQ-Contest wrote:
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
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