Project Horus High altitude balloon project


Another radio test a new yagi

I made up 1.3m yagi yesterday - the biggest that'll fit in the boot of my car :) . I used K7MEM's excellent yagi designer to come up with a plan, and cut the pieces from aluminum tubing, which I had TIG welded at a local machine shop for $20. My folded dipole is made from a length of copper tubing, but I don't have much faith in it - it was difficult to get it sized correctly. I suspect I may need to swap it for a better one after I do some proper testing on the antenna.

We tested the radio again last night, using the coat-hanger yagi, and the larger yagi. The coat-hanger yagi was brilliant considering the effort invested, and is much more practical than the large (1.3m) yagi. It's nowhere near as directional as the larger yagi, given the lower number of elements, and is extremely lightweight - so it's super easy to use with 1 hand.

As I found out, two hands are needed for the large yagi, even though it's lightweight (being aluminum). Even using two hands, it's very difficult to keep it exactly on target, and it's extremely directional. I've since made mounted it to the quick release block on my tripod, which should keep it pointing where we want.

We tested the same distance as previously - from the airport to Belair, as well as going out further with the yagi's. The coat-hanger yagi performed brilliantly at the airport, getting an excellent signal (where the 1/4 wave whip we used last time struggled). Going out further to outer harbor, the coat-hanger yagi was struggling to pickup anything decodeable, but the larger yagi did the trick. Total distance from outer harbor to the transmitter was 27.5km, with a very poor line of sight, and only 300m or so at the transmitter side. Overall quite successful, though I suspect the large yagi is capable of much better performance with some tuning.

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