Re: 40m Delta Loop


Of course the downside, as Tom pointed out, is that a Delta Loop takes longer to erect than, for example, an End-Fed wire. That could make it less suitable for a RaDAR exercise. I am also experimenting with other antennas involving a full wavelength of wire. 137ft is about 5% long for a full-wave on 40m but that is the recommended length for a delta loop. I also plan to setup the same wire as an End Fed Wave antenna. That's an interesting concept inspired by the US Marine Corps who used wires one or more wavelengths long, hung in a straight line, close to the ground, for HF comms in the Vietnam era. A signal along the wire interacts with its image in the ground to produce vertically polarized propagation off the end of the wire. EZNEC modeling suggests a height of about 8ft produces a lossless antenna with a takeoff angle around 55deg. If the wire is any lower (e.g. on the ground) the losses are considerable but the takeoff angle is even lower. If the wire is too high it becomes an NVIS antenna. Another variant is the End Fed Half Rhombic antenna which uses the same length of wire supported in the middle by a 30ft pole.

The purpose of the exercise is to find antennas that will keep QRP field operations alive during the solar minimum. Two or three years ago I worked DX with just a homebrew buddistick but the bands are getting a bit tricky as we pass through the solar minimum for the next couple of years.

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