Wednesday 12 June 2013

Project 9: A coax collinear antenna for ADSB

           Another VERY quick antenna project to enable better reception for my ADSB system. I used the method described here: by Dusan Balara (thank you!).
           The antenna is simply 8,12 or 16 (i went for 16) 116mm (plus 50mm) sections of coax, with each end of each section stripped allowing 25mm of solid core which is then inserted between the outer jacket and braid of the next, giving it an offset appearance. A small piece of plastic is placed between each of the core sections to avoid shorting. The joins can be taped if you're in a hurry, but i love using heat shrink and it restricts movement better.
16x116mm sections
plastic squares for insulating the cores
keeping the cores insulated
a small section of the completed 2metre long collinear. note the off center appearance.
The finished product (center) , added to my growing farm.
           A 2 metre section of sparkies conduit from bunnings is used to house and protect the collinear, seal the top (i found an old cap from a roll of copper that a plumber left behind), seal the base and up she went.
           This was the fastest of my builds to date (taking just over 45 minutes) and the cheapest. 2 metres of 75ohm RG6 cost $2, 4 metres of conduit ( i will use the other 2 metres on my next project) cost $4. I don't know how much this antenna would cost to buy, but i'm certain it won't be $6!!
           Apparently this antenna is said to have excellent "horizon" qualities, and this is indeed the case. In testing this evening, i am receiving aircraft far earlier and losing them far later than last nights session with the discone.

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