[CQ-Contest] delta loop question 80m

[Fco. Luis Delgadillo]

Tony,

Great valuable information!

I will build  one to test it. Would you mind send a photo and more details of the stub.

I  shared the previous  info to our club, and some members are already interested on building it.

73

Luis XE2B

________________________________
De: CQ-Contest <cq-contest-bounces at contesting.com> en nombre de Tony Brock-Fisher via CQ-Contest <cq-contest at contesting.com>
Enviado: lunes, 29 de julio de 2019 05:47 a. m.
Para: reflector cq-contest <CQ-Contest at Contesting.COM>
Asunto: Re: [CQ-Contest] delta loop question 80m

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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