Hold on there Bradley...|
An antenna that is built for a higher frequency than what you are inputting will exhibit downtilt in its original orientation.
bradley glen wrote:
Hi All I agree with Kevin and have used this in the commercial field where the anteena was originallt cut higher than was to be used.I mounted the antenna upside-down and had good results-with some noticed downtilt which was good for the application .On the same token keep in mind that most of the efficiency of the collinear design lies at the first radiating element - reduced radiation as one extends to the end of the antenna. Good luck Regards Bradley glen zs5swt /zs5wt --- Chuck Kelsey <[EMAIL PROTECTED]> wrote:Thanks for saving me all the typing ;-) Chuck WB2EDV Kevin Custer wrote:I think what Chuck was getting at was the'automatic' beamtilt of avertical omni collinear (usually fiberglass) whenit is run outside ofits specified bandwidth. As a function of theelement length in acoaxial collinear as compared to the appliedfrequency, the verticalbeam pattern will change with applied frequency.If a coaxial collinearis fed with a signal that is exactly on its designfrequency, thevertical beam pattern will be centered about theantenna, and theantenna will be at its highest radiatingefficiency. If a coaxialcollinear is fed with a signal that is 2% lowerthan its design, theantenna will exhibit a vertical beam downtilt ofapproximately 3 degreesand suffer approximately 10% loss in overall gain.If a signal that is2% higher than the antenna design is fed into acoaxial collinear,vertical beam uptilt of approximately 3 degreeswill occur, and again aloss of overall gain. These instances are not the case with binary orcorporate fed dipolearrays, as the phasing harness predominantlycontrols the vertical beampattern. Beam Tilt and efficiency doesn't changevery much with appliedfrequency, and is one reason that the exposeddipole array is a betterchoice where wide band operation is required. Kevin Custer skipp025 wrote:Kind of loaded question/statement/answer really.Allantennas have both horizontal and verticalbeamwidth.Depending on what you think is beam-tilt... onecouldand some do say all antennas have a beam tilt andora beam width. Others combine the description... In the more commercial world of antennas, we nowseevertical omni repeater site antennas withadjustablebeam tilt. But I'm not sure if I'd say they have to be madewithfiberglass radomes (covers). There's more thanone methodused by the various mfgrs to adjust the beam tilt- beamwidth. For the most part we only see some modelswithadjustable setting in some vertical omni modelswithcomposite radomes. ... and you pay serious money for the adjustablebeamtilt models. If you pay attention to the specs,you'llsee values for the horizontal, vertitcal beamwidth andwhere needed, the/any adjustable beam tiltvalues.Your results will probably vary... cheers, skippYahoo! Groups Links [EMAIL PROTECTED]__________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
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