02 May 2010

Cheap 144 and 432 MHz yagis for portable use

It is summer soon and for me it would be nice to have yagis for 144 and 432 MHz to be used when QRV portable. My home QTH is very bad for VHF and up. The only solution for me is to find a better place in the neighbourhood. Drive there and put up an antenna on a small telescopic mast. WA5VJB has designed cheap and very easy to build such yagis. I first built a 6 element yagi with a rectangular wooden boom. But the boom was sensistive to rain etc. so instead I built another one with a 50 mm plastic tube boom. Today I went to an open field nearby to test the antenna by listening to a 144 MHz beacon 300 km away. It was not easy to hear the beacon because of strong aurora. The receiver was a Yaesu FT-817 and 10 m RG8 coax to the antenna. You can hear the aurora sigs in the video below.

Material:
Boom, 50 mm Plastic tube, 1x2 m, 70 SEK Biltema
Elements, 6 mm Aluminium tubes, 5x1 m, ca 350 SEK, Bauhaus
Driven element, 3/16" Copper tube, 5 m, 159 SEK, Biltema

Performance:
Without trimming the driven element: WSVR estimated 1:1.4 @ 144.3 MHz, measured with a Bird wattmeter
Gain not measured, maybe it is ca 9 dBD


video

I have also built an 11 element 432 MHz yagi according to WA5VJB design, but I have not tested the antenna in the field yet. The elements are made from welding rods and the driven element is made of a copper tube. The boom is a rectangular hard wooden boom.

Material:
Boom, 13x40 mm hard wood, 2.4 m, ca 160 SEK, Bauhaus
Elements, Welding rod (probably iron), 3.2x350 mm, 1 kg, ca 80 SEK, Bauhaus
Driven element, Copper tube, 4 mm, Found in my shack

Performance:
Without trimming the driven element: WSVR estimated 1:1.7 @ 432.2 MHz, measured with a Bird wattmeter
The resonance is too low without trimming, maybe 420 MHz
Gain not measured, maybe it is ca 10 dBD