Antenna Shootout 2021 – Bob (G4PVB)

| June 16, 2021 | 0 Comments

My antenna is a 2m folded dipole designed by Dave Kimber, G8HQP. I followed his instructions like this: 

2m Folded Dipole – a loft-mounted vertical folded dipole for the 144 – 146MHz band. Theory: A vertical antenna most appropriate for 2m. A fat dipole (therefore wideband) will have a lower feed impedance at resonance than a thin dipole so 50Ω feeder cable e.g. RG58C/U may be used. It’s an economy, lossy cable (best to keep the length less than 10 metres) for low power use and has a stranded centre conductor so less likely to break if the cable is bent. The conductors are tinned so easy to solder.

Making it: The dipole is made from 2∙5mm2 × 90cm long power cable: strip off the outer insulation then use the two insulated cables to make the two elements of the dipole. Use a twisted pair of 1mm2 lighting cable cores 63cm long to make the balun. There is no direct connection from the coax screen to the dipole. The return current gets back across the capacitance of the balun. This is all assembled using a chocolate block connector. Coil up the balun to save space. The match to 50Ω cable is good.

For the antenna shootout mine is mounted on a camera tripod with a runner bean bamboo pole extension to give a total height of 4.5m.

The photos below show the circuit diagram g4pvb-01, the coiled-up balun g4pvb-02 and the whole antenna itself with black RG58 hanging down near the black element g4pvb-03.

I did not have red/black for the balun so I used blue/brown.

By accident I found it works on 70cm too with my little handie. I got as far to the Harrow repeater with just one Watt.

More information about this antenna can be found here.

Bob – G4PVB

Category: Club News, Shootout

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