moxon-yagi beam antenna for 20m,15m
DESCRIPTION
Easy to build HF beam for 20m,15mTRANSCRIPT
Moxon-Yagi beam antenna for 20m and 15m
Built by ZS1JHG
Les Moxon G6XN was an innovative antenna designer and published an excellent antenna book “HF Antennas for all Locations”.In this book he made experimental improvements to theFred Caton VK2ABQ beam antenna.LB Cebik W4RNL has improved further on Les Moxon`s work and credited his design with the Moxon name.
I have built many antennas but none of them performed as wellas the Moxon on 20m. The front to back is at resonance over 30db and forward gain close to 6dbi.
My antenna is built from four heavy duty fibreglass fishing pole blanks.The centre support is a plastic compound, marine multiply (12mm)can also be used but needs to be painted with an outdoor paint.The fishing rods are attached to the centre support with shimmedgalvanised conduit saddles and stainless steel bolts and nuts.The feedline support pole is pvc electrical conduit.
The feedline used is foam 300ohm heavy duty ribbon which close to the radio room is fed into a 4:1 balun and short 50 ohm coax to
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the transceiver. This enables the antenna to work on 12m and 17m via the rigs built in auto atu.The driven element spacer/feedline connector is made from Perspex as shown in the drawing. The spacers between reflector and driven element were also from Perspex. For good performance this gap must be maintained accurately.The antenna wire used was 1.8mm solid copper, but I wouldrecommend using black plastic coated stranded wire as it ismore robust in windy conditions.Total Driven element Length 10.06m Freq 14.150MhzTotal Reflector Length 10.58m Freq 14.150 MhzThe Gaps between the two held to 0.22m on the Perspex spacersThe Reflector for 15m (21.200 Mhz) Length 7.01m spaced 0.78mfrom the 20m reflector.
Reading taken with an MFJ 259B analyzer ,antenna at 40ft
Freq SWR R X14.250 2.3 121 0
21.250 2.8 159 0
18.150 2.6 43 50
For further info on Moxon beams and a frequency/length calculator programme see the ”Moxon Project” website.
A rough drawing of my antenna which is minus the 10m reflectoris shown below :
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