Delta Loop for the 20m band

A delta loop antenna is not particularly suitable for SOTA. It requires much more space than a vertical and the set-up is more complicated.
Nevertheless I’d like to show this design here because sometimes space (and weight) don’t matter and a low take off angle is welcome.
A possible application could be the VK/ZL/JA <> EU S2S event or the Trans- Atlantic S2S QSO party .

loop1
Delta Loop on HB0/Li-004, Augstenberg, 2359m a.s.l. during our DX-pedition to the Principality of Liechtenstein in September 2013. DL4AAE worked many JA’s on 20m with 100 W output power.

Design:

Uwe, DL4AAE, ran various simulations in order to optimize the „classical“ delta loop design. He summarized the results in an excellent presentation here (German only). Based on his design I built the following delta loop:

Delta-Loop_design

Dimensions (optimized for 14.050 kHz):

h0 = 2,0m
h   = 4,0m
a   = 0.7m
x   = 4.88m
U   = 22.5m (Umfang/circumference)

The circumference has been calculated for a wire with an inner diameter of approx. 1.6mm (conductor) and an outer diameter of 3mm (insulating material PVC).

Details of the design are shown below:

feed
Feeding point with pull relief (not weather-proof but acceptable for most activations).
corner
Lower left/ right corner of the delta loop with fixed insulator.

The shown design requires a pole of just 6 metres length. However, a 6m pole is not recommended because the top segment is way too thin to withstand the force acting there. We use a 10m GRP pole instead. Not used segments have been removed. The wire runs loosely through an insulator at the tip. This makes it easy to center the loop.

loop3

The Delta Loop can be fed with coaxial cable and does not require a BALUN. However, make sure that the feed line does not touch the antenna wire. It should be routed in such a way that it runs at a right angle to the loop surface.

Performance:

The bandwidth of this design is huge. If tuned to 14.175 kHz, it will cover both, the CW- and SSB- portion of the 20m band.

SWR
SWR plot of the delta loop optimised for 14.050 kHz

Thanks to the mostly vertical polarisation, the vertical take off angle is approx. 20° and doesn’t change much with ground properties.

radiation_pattern_v
Vertical radiation pattern (chart normalised to 3.5dBi)

The horizontal radiation pattern is nearly omnidirectional with its maximum perpendicular to the loop.

radiation_pattern_h
Horizontal radiation pattern (chart normalised to 3.5dBi)

Conclusion:

The new design of the delta loop has several advantages:

  • impedance approx. 50 Ohms, thus no matching required
  • feeding with coaxial cable is possible
  • large bandwidth
  • low take- off angle
  • ground properties have little impact on take- off angle

It could be worth trying it on a summit…

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2 Gedanken zu “Delta Loop for the 20m band

  1. ve3ips 26. September 2017 / 21:49

    I like this a lot and will build one this weekend. Thanks for this design

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