[Antennaware] re vertical with metal roof as groundplane.
george_warnock at hotmail.com
Sun Mar 1 10:12:05 PST 2009
Hello there again....my thanks to k2av guy and pete ny2r for contributing to the most interesting subject..I saw an opportunity arising with the building of this workshop to contribute to the efficency of my station, I knew there was a learning curve involved but did not realise how little I knew...it takes me a little while to interpet what I have been told, but because of the clear and consise manner it has been explained my knowledge has grown considerably...there are one or two points I would like to expand upon so I hope that guy k2av would be good enough to help out...guy my "need" as you describe is non hemispheric, so as you describe I will pull the two radials to opposite quadrants, and will cut them to meet the impedance requirments....if you recall my roof structure is of the pitched or angled variety with a pitch of 20 degrees, to facilitate the opposite quadrants of interest to me, the radials will be following the pitch of the roof and dropping the 20 degrees, is this a disadvantage? perhaps it does not matter when as you say the radials are only there to act as a current sink to complete the feed point connection,there is another factor perhaps worth considering here the building is 40 feet by 30 feet, the longer part being the "ridge" level or horizontal part, another thing concerning me and I have read different opinions on the subject is how high should the feed point be above the roof structure some folk say as close as possible, but another thought is, if above the roof somewhat the angle of the radials can be varied to effect feed point impediance... again this will proberbly not apply in this case...my instinct is to try and take advantage of the situation I have with this proposed structure "workshop" and its metal roof, 40m seems to be ideal, but not having anything worth while for 80m, I am wondering if a vertical covering two bands is feasible and what advantages or disadvantages there is in such a structure.
reguards to all george
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