有空再译,或有谁帮译一下。
总之,原理是,利用电感、微调电容与盒子里的馈线形成四分之一波长的短截线,利用短截线来滤波。微调电容可用来不同频点。
On the left hand side of this circuit diagram a 433MHz 1/4 wavelength coax stub is indicated that is effectively short circuited at the outlet end by a series resonant L/C circuit tuned to 433MHz. This arrangement presents a very high impedance for 433MHz signals at the input (ie top connection) of the device, but will freely pass 144MHz signals. Similarly on the right hand side of the diagram, a 144MHz 1/4 wavelength stub is indicated terminated with a series resonant L/C circuit that is tuned to resonate at 144mHz. This side of the circuit will block signals at 144mHz, but will pass 433MHz signals unhindered.
Dimensions for the 1/4 wavelength stubs are given, but depending on the particular coax cables used, some experimentation might be needed, especially for the 433MHz stub. This isn't too difficult. My procedure for setting up this diplexer was as follows:
1. Connect low power transmitter with SWR meter to the input connector.
2. Connect 50Ω dummy loads to output connectors. Dummy loads can be two small 100Ω resistors connected
in parallel across a BNC plug.
3. Adjust the trimmer capacitors for minimum SWR readings.
4. If SWR readings close to 1:1 cannot be obtained then try using slightly different stub lengths. It was fairly easy
to find the optimum length for 144MHz. The 433MHz stub length was more critical.
I built this diplexer into an aluminium die cast box as shown on the left. The device continues to work very well, giving very low SWR readings on both bands.
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