Same antenna for tx and rx

Projects LimeSDR
#1

Hello everyone,

I’d like to use LimeSDR usb as amateur radio on VHF and UHF. Unfortunately I have only one good antenna.
I’d like to know how to make from LimeSDR some kind of ICOM-705.
Can you advice what kind of antenna tx and rx antenna mixer for same frequency?

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#2

There are a few ways to do this:

  1. use a T/R switch - when receiving the receive port of the SDR is connected to the antenna. When you switch to transmit, you switch the transmit port over. This can be done with some PIN diodes - you can buy ready-made from https://www.pasternack.com/pages/RF-Microwave-and-Millimeter-Wave-Products/pin-diode-switches.html or other sources.
    You could also use a physical relay, but that will take longer to switch.
  2. IF you are using a split frequency, you could use a pair of RF filters to separate the signals - this is commonly referred to as a duplexer. That’s how normal 2 meter FM repeaters work. The big (literally) problem is that to make a good duplexer at 140MHz takes something about the size of a soda fountain CO2 bottle - not exactly portable.
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#3

I’m interested in LimeSDR to build a repeater in the 368 Mhz band.