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Reversible 40m Delta Array Delta loop arrays are great DX performers on 40 meters- their gain and directivity help pull out the weaker signals |
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This is an interesting version of the ever popular 40 meter delta loop
beam that was built by
K4TX/K4GE.
It is quite effective for a relatively simple wire array.
Two things contribute to its top notch performance- the clever use of
3/8 wavelength feedline sections to tune the non-driven loop as a
reflector (as seen on the K3LR 160m sloper array),
and the 'upside-down' configuration with the point of the
delta at the bottom. This increases the effective height of the antenna
over the more commonly used point-up configuration. The antenna has good
F/S rejection and around 10-15dB F/B, which can make all the difference
between hearing or not hearing weak DX signals on a noisy band.
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| For 7.0 MHz, the lengths of the two 3/8 wavelength feedline sections should be about 34.8 feet with polyethylene dielectric coax (velocity factor .66) such as RG-58, RG-8, and RG-213. For foam dielectric coax such as RG-8X (velocity factor .81) the best length is 42.7 feet. This affects gain and directivity but is probably not highly critical. For mid-band, 7.15 MHz, the respective lengths are 34.0 feet and 41.8 feet. Note that the Ameritron RCS-8V does not switch both the center conductor *and* the braid of the coax, as stated by K4TX. All connector shells are grounded to a common point on the circuit board. He does report that his antenna works very well, however. Regular coax switches probably should not be used with this antenna. You might want to build your own remote switch box for this antenna switching scheme. |
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