Lying in the shed was an old J-beam 4 element yagi, all bundled up and was last used many decades ago, but showed promise for revival. I also had a longer section of boom with the reduced section on the end which I think had been off a tv aerial in the past, and together made up about 3metres in total. A bundle of spare 2m elements in the collection all seemed suitable candidates and I set to work. The driven element was stripped down and cleaned, new bolts fitted, all the mountings for the elements were wire brushed and oiled making them useable, but the additional elements had no mounting hardware. In the garage was a bag of the little blocks (pvc ?) which you join furniture boards together with, and a minute in the microwave proved they didn't get hot so seemed like a suitable material. Putting two of them together in the vice in the pillar drill made it easy to drill a hole down half and half between the 2 blocks for the elements, and a router bit made a good job of making one piece a good fit against the boom, so with a new supply of stainless M5 bolts, washers and wing nuts dropping through the letterbox right on cue it was all put together. A new feeder tail was fitted to the folded dipole, and just before the rain arrived it was tested out with a thruline and put in place of the 2x 7element ZL-specials on the mast. Beacons were checked and the usual ones received ok and even a qso with Anglesey proved the reborn item was working. It will be proved out better when some stronger signals are received, but the beam pattern seems to be as expected for a 9 element yagi. Due to some elements now being insulated from the boom their lengths are probably not quite optimal so there is still room for improvement, and probably a longer boom would not be too obtrusive :-)
(the higher it is the smaller it looks !)
29/4/13 Results on-air at present are quite encouraging, the PI7CIS 144mhz beacon is still about the same strength as before, dependent on the aircraft crossing The Wash at the time, there is a marked enhancement of the signal due to aircraft reflections, the Jumbo 747s and big Airbus jobs at 37,000 ft are obviously the best, the signals via the smaller 737s and 319s etc are noticeably weaker, it is convenient that there seems to be awell used air lane in that area, which doesn't always apply with beacons elsewhere. See screenshot below.
A few photos of drilling and milling the blocks, and lots of swarf !.
(the higher it is the smaller it looks !)
29/4/13 Results on-air at present are quite encouraging, the PI7CIS 144mhz beacon is still about the same strength as before, dependent on the aircraft crossing The Wash at the time, there is a marked enhancement of the signal due to aircraft reflections, the Jumbo 747s and big Airbus jobs at 37,000 ft are obviously the best, the signals via the smaller 737s and 319s etc are noticeably weaker, it is convenient that there seems to be awell used air lane in that area, which doesn't always apply with beacons elsewhere. See screenshot below.
A few photos of drilling and milling the blocks, and lots of swarf !.