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VHF/UHF Ground Planes (2 replies)
Regarding the ground plane, the overall size should be about a quarter wave length from the feed point of the antenna. Extending beyond this limit will be unlikely to show any real advantage over the basic design. A simple light weight ground plain can be constructed as shown on this link. http://www.ai4ji.com/Projects/GroundPlanes_page1a.gif
Hope this helps.
Neil
G7AQK
I made a 1/4 wave identical to the one in the link Neil G7AQK posted above.
I used copper wire from household twin & earth electric cable. I stripped off the plastic coating and stuck the antenna up in my loft so wind etc is not a problem.
For positioning an antenna outside and at the mercy of the elements it would be quite simple to use 20mm plastic pipe fitted over the elements and into a watertight electric junction box.
Mastic for sealing the plastic pipe into the junction box is good but you can get a watertight screw in pipe housing that will make the fitting and waterproofing of the antenna so much easier
So I am told, my 1/4 wave cheap & cheerful antenna gets out rather well.
73's Bri M6UHN
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I'd like to put up a simple 2m/70cm antenna, in a limited space on our flat roof, and to be somewhat conspicuous. There's no chimney to strap a big white tube to, unfortunately.
At the moment, my home 2m operations involve a temporary Slim Jim antenna on a fishing rod. However, I've also been using a mini-mag aerial on a metal pie tin, and because it's light, I can put it on a [weaker] higher roof and actually achieve a better signal.
One of these: https://www.google.co.uk/search?q=Nagoya+UT-106UV&safe=off&rlz=1C5CHFA_enGB503GB503&es_sm=91&tbm=isch&tbo=u&source=univ&sa=X&ei=lALlVId4ye9q_qiCsAk&ved=0CDoQsAQ&biw=1149&bih=683
Regarding ground planes — the pie tin isn't electrically connected to ground, nor earthed. Would I improve performance using a large metal sheet, and connecting it electrically to the coax ground? How large?
For a more permanent aerial (since I can only use this one when the sea winds are light), I'm planning to make something to the same dimensions, with a proper ground plane, anchored down.
Suggestions appreciated!