Sunday, 17 March 2013

Antennas for show

Time has come to start thinking about the show - The 2nd Lions Doncaster Show. If at all possible we want a dual HF set-up this year, one on 40m fixed, and another to be 'frequency agile' to help get around the NFD contest. Im very much disinclined to bother with 2m FM this year, unless I can secure a couple of day operators extra. If we do have 2m, then a lightweight antenna is needed, the 1/2w commercial being too heavy.

We have a new (to us) 27ft mast - an ex-army Larkspur telescopic. This will hopefully provide the main HF antenna, using the Clansman antenna wires, in an inverted V. Im missing the three guy pegs at present but im sure those can be found before september.

Since im looking into antennas for the show, and since im also looking to rig something up for the VHF marine band, my thoughts have turned again to the fibreglass parts and mountings of an old colinear I have. After looking at various ideas, we come back, as always, to the Slim-Jim. Nothing special, the Slim-Jim, but remarkably easy to build. Trouble is, although I have plenty of 450 ohm window line, this is too wide to fit in the fibreglass tube of the old colinear. I could bend it over a little, securing it in its new shape with cable ties, which will allow it to fit but of course change the characteristic impedance.

Another idea, is to build a slim jim from the huge amount of high current twin cable I have. This has a spacing of about 3mm! I might give one a try and see if it can be done.