CQ-Contest
[Top] [All Lists]

Re: [CQ-Contest] delta loop question 80m

To: Tony Brock-Fisher <barockteer@aol.com>, "cq-contest@contesting.com" <cq-contest@contesting.com>
Subject: Re: [CQ-Contest] delta loop question 80m
From: Edward Sawyer <EdwardS@sbelectronics.com>
Date: Mon, 29 Jul 2019 09:17:18 -0400
List-post: <mailto:cq-contest@contesting.com>
I no longer do this at my current station but used to have an 80M delta loop 
(single) and did exactly what Tony suggests.  I used open wire - 450 Ohm line 
as the stub and I just had a shorting clip to short circuit the stub at the 
base of the delta loop for SSB and unclipped it for CW.  Vertically polarized 
exactly as Tony describes.  For 2:1 Bandwidth, I have never seen a way to use a 
delta loop from 3850 - 3500 vertically.  It might be possible horizontally but 
if so its only because the low height above ground is making it so ineffective 
for DX the impedance is broad.  Not a good way to achieve the desired results.

73

Ed  N1UR

-----Original Message-----
From: CQ-Contest [mailto:cq-contest-bounces@contesting.com] On Behalf Of Tony 
Brock-Fisher via CQ-Contest
Sent: Monday, July 29, 2019 8:47 AM
To: reflector cq-contest
Subject: 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

_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest

<Prev in Thread] Current Thread [Next in Thread>