In theory, it would sort of work for receive. But don't try to TX through the array as it would create interference to other users on adjacent frequencies on TX (NOT GOOD).
Now as far as the RX application; If you think about it those adjacent frequency users would also mix with the switching frequency and become interferers to your desired RX frequency. Interesting idea if it could be made to work.
However if you have a second receiver, no reason you could not have a diversity RX setup to select best polarization.
Hi all, Has anyone ever considered the possibilty of using PIN diodes and a free running square wave oscillator to electronically switch between RHCP and LHCP? The switching frequency would have to be high enough so as to not introduce a tone to the signal.
Just a thought I have had for awhile.
RoD KD0XX
Joe,
Makes a good point about this as appropriate as a receive-only system.
To answer Rod: Pin diode antenna switching has been done by radio astronomers for years in what is called a Dicke Receiver. They switch at audio rates between the antenna and a noise reference source to track minute gain variations in the receiver.
The basic problem with your approach is that half of the time you will be in the wrong polarization, leading to a 3-dB overall reduction in sensitivity. The approach I outlined with dual receivers eliminates this. But functionally a pin diode can be used for switching and controlled by a square wave at any desired rate up to the limits of the pin diodes response.
For a transmission system that will adjust to polarization changes. The simplest is merely a coax switch to chose the best polarity at the time. A more advanced system would use programmable phase shifters to accomplish exactly what polarization is desired (if you have a gov't budget, that is).
My bottom-line question to all these schemes is how you are going to determine what the best polarization to chose? This is not a simple exercise in orbital mechanics and solid-geometry. The Ionosphere adds Faraday rotation at random. If you can predict Faraday then you probably will make a fortune in weather predictions, too! ;-)
73, Ed - KL7UW
At 11:49 AM 1/4/2009, RFI-EMI-GUY wrote:
participants (2)
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Edward Cole
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RFI-EMI-GUY