Re: Streetsweeper Antenna / option

Subject:

Comments:
: This would be nice...unfortunitly I do not think it would work well under the chassis since it would probably hit a bump and knock off, as well as many other problems... : Thanks for the idea though! : : : : I not certain what you really want to accomplish here but I'll throw this in for comment and see where it goes: Take a look at the ANTENEX "phantom" whipless antenna. You could mount this stubby loading coil in the rear window package shelf, in the grill near the radiator, inside one of the tail light housings, or under the chassis like you originally thought. ????? : : *************** : : : Crossed polarization in the real world is probably worth at least 6 dB, : : : but it sounds like you won't have line-of-sight anyway. The signal : : : will squirt out from under the vehicle and stay low - the energy : : : reaching the Rx antenna will have been randomly reflected by obstacles, : : : and won't have any consistant polarization, so don't sweat it. : : : A waveguide is some sort of hollow structure where the signal is : : : constrained between conductive walls (usually rectangular or circular : : : for easy analysis and construction). The size is picked to match the : : : frequency of use. In the vehicle case, you have an upper conductive : : : surface but the lower one could be conductive/reflective when wet or : : : absorbant if dry and loose. The sides are mostly unconstrained, so : : : it's not really a waveguide - I was stretching it a bit. But still, : : : the transmit signal "pattern" is highly dependent on the geometry of : : : the objects in the near-field, and it's probably faster to try it and : : : see than to get the s/w and build the models for computer analysis. : : : As for Rx antenna height, you want line-of-sight at UHF. Keep it low : : : if the vehicle is within sight, but raise it if you're counting on : : : stray reflections. Good luck!