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Jul 12th
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Home HAM Radio HF Antennas 80m vertical deltaloop

80m Vertical Deltaloop

With the apex at 27meters (!), this vertical deltaloop is an interesting alternative to the quarter wave vertical I have been using most of the winters. Main reason for trying out this antenna, is the fact that it doesn't require any ground system/radials. A great advantage in my situation, where most of the antenna's are deployed in a farm field during the winter, but all must be removable within 24 hours upon notice. The loop is strictly equilateral, all three sides measuring 1/3Lamba, which at 3.8Mc equals 26.32meters. The feedpoint is located at precisely .25Lambda (19.74 meters)  from the top. Feeding the loop at this point gives maximum suppression of NVIS-signals. I made this loop using 1.6mm aluminium wire: cheap, light and very strong. Two disadvantages: can not be soldered, and kinks very easily.

photo 1: the loop, apex at 27 meters

the 80m deltaloop in its full glory

 

photo 2: the tower carrying the wire deltaloop

the tower - a surplus mast from the Bundeswehr

 

photo 3: yet another photo of the loop. Note the black top-section, being a spare mast from a surfboard ;)

and yet another photo ...

 

photo 4: professional self-clamping guy-wires

self-clamping guy-wires

 

Measuring the loop's parameters

Using the AIM4170 the following plots could be made.As can be seen, the loop is resonant at 3.807Mc, which is very close to the calculated value of 3.8Mc?!
The impedance at the resonant frequency is roughly 150Ohms.

80m vertical deltaloop

 

Modelling the loop using 4NEC2

To get a better feeling for this antenna, I also modelled it using the great 4NEC2 program of Arie Voors, check it out at http://home.ict.nl/~arivoors/.
Here are some screenshots you may find interesting:

figure 1: wire model 80m vertical deltaloop

wire-model 80m vertical loop

 

figure 2: vertical radiation pattern - this is a DX-performer!

vertical radiation pattern

 

figure 3: 3D radiation pattern

3D radiation pattern

 

figure 4: impedance plot (based on model!)

4NEC2 model-based impedance plot