7 element 70MHz DK7ZB Yagi (28ohm) GW4RWR

Introduction
After a few years on the band, I thought I should treat myself to a bigger antenna.

The common advice is to use 1" square boom. I was keen to use round tube, to keep the weight down slightly. It does make drilling parallel holes more tricky. I assembled all boom sections, used cotton thread taped at both ends and pulled taut to draw lines element positions on one side. To identify where the holes on the other side should be drilled (never be tempted to drill all the way through the boom - it's sure to end badly), I took a rectangles of paper, wrapped it around the boom, marked the overlap, and cut off that overlap. Remove the paper, fold in half, re-wrap around the boom, and use the fold to identify where the other-side holes should be drilled. The supporting arms were made from boom offcuts, bent (blow torch treatment) at both ends until they're parallel with the boom.

The radiator feed box came from a 3 element Band II antenna picked up at Llandudno rally. Insulated mounting clamps (1/2" dia) came from nuxcom.de and all the aluminium was from aluminiumwarehouse, Hatfield.

Dimensions/mm
Distance     Length (12.7mm elements)
0                  2098
690              2033
1185            1960
2300            1900
3630            1872
5260            1870
6515            1830

Results?
This was finally erected in time for the 2014 Es season. It's certainly more unwieldy than the old 5 element.

DK7ZB calculated a gain of over 10.8dBd. I measured a return loss of 16dB. A side by side comparison with the 5ele confirms more gain. I can hear GB3RAL all the time now, previously it was at the noise floor. Inevitably the beamwidth is narrower - I'm going to need to use the rotator - the 5ele could be oriented south east and forgotten about!

Now let's work some DX.