315 MHz CP antenna?
315 MHz CP antenna?
(OP)
Anyone have any suggestions for designing a dual polarization antenna for a receiver. I have a small key fob with a loop antenna, but the user can hold it in any orientation. Obviously, when he holds it so it is cross polarized with my monopole antenna on the receiver, she'sa no work! I was thinking if there were some sort of dual polarization antenna on the receiver front end, it would not really care what way the key fob was held (although there might be a 3dB hit in maximum received signal). I saw a TI patent (5,592,182) for a dual crossed loop design that was supposed to be CP. Anyone know anything about this, or another cool way to do it.
So in summary, I have a single polarizaton (loop) antenna in a key fob that I want to receive with a dual polarization antenna on the reciever so that it would be relatively insensitive to user operation.
So in summary, I have a single polarizaton (loop) antenna in a key fob that I want to receive with a dual polarization antenna on the reciever so that it would be relatively insensitive to user operation.





RE: 315 MHz CP antenna?
Dan - Owner

http://www.Hi-TecDesigns.com
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
Dan - Owner

http://www.Hi-TecDesigns.com
RE: 315 MHz CP antenna?
Personally, I'd look at getting a better alarm (?) system. There are two-way systems advertised with 3000 foot ranges.
Or park closer.
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
Note that you'll still have a -3dB penalty as compared to the optimally-aligned linear, when receiving a linear wave. So you'd need 1100+ foot peak range to start (neglecting feed harness losses).
Disclaimer: I don't think anyone has ever found happiness in a car alarm. Once you have the perfect car alarm, someone will probably steal it.
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
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And yes this is Part 15.
RE: 315 MHz CP antenna?
Hint: 315 MHz isn't far off the UHF Military SatCom band and they also use CP. If you Google around, you can find designs for Crossed Yagi antennas designed to receive MilSatCom signals and some of those designs will include details for the phasing harness. However, your antenna's elements might have a different feedpoint Z than the Yagis.
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
RE: 315 MHz CP antenna?
If you can possibly do directional, helical is the way to go. We are doing a set of helicals with a switch to get omni, that would probably double your range.
kch
RE: 315 MHz CP antenna?