The antenna I am now going to describe is one that I designed some time ago. It is a high gain quad beam for 2M (144 – 146 MHz) band. The forward gain of such an antenna is approximately 11.5 to 12dBd, that’s approximately 10.6 to 10.8 times the output power from the rear of your transmitter. For example, say you were operating a 10 Watt txr, the effective radiated power (erp) would be 10*10.6=106 Watts.

All this power and still a relatively small antenna; the boom is a mere 1 metre in length and may be constructed from 1” (2.5cm) square, weather treated, wood. The elements are constructed from 2.0mm diameter enamelled copper wire (ecw), the dimensions of which are shown in Table 1.

All the dimensions were calculated using the formulae in table 1, which was, admittedly gleaned from “The Amateur Antenna Handbook” by William I Orr, W6SAI, although the beam is of my own design.

• Reflector element (per side) (L1) = 78.7/f MHz metres
• Driven element (per side) (L2) = 76.6/f MHz metres
• Director elements (per side) (L3, L4) = 74.3/f MHz metres
• Element spacing (s) = 43.3/f MHz metres

Table 1

For horizontal polarisation feed from bottom for vertical polarisation rotate by 90◦

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Please note that the lengths in Table 2 are per side so for the full loop perimeter you will need to multiply by 4. Also, for any USA readers, these lengths are in metric meters.