Hello everyone,
I am working on an LMR radio project near the NYC area. The goal is to extent the two way radio coverage from an existing site via a hybrid DAS system to a large warehouse environment using GTR8000 base stations to generate the many simplex VHF frequencies for the client's LMR operations. On this antenna system we are also looking to pick up off-air first responded frequencies in the UHF/800MHz range. This means that the system will work with simplex and duplex frequencies. For the system to cater to all frequencies we have decided to combine all the TX frequencies (off-air TX and base stations TX) and all the RX frequencies. The TX frequencies will be transmitted throughout the warehouse via dedicated transmit antennas and the RX frequencies will be picked up via dedicated receive antennas. Since this site has many metal and concrete obstructions we have to place many antenna pairs(TX/RX) throughout the site. For the UHF/800MHz frequencies I am not so concerned as they are duplex but for the VHF I am worried that the transmit antennas will interfere with the receive antennas as they are receiving and transmitting on the same frequency. What are some ways to avoid this interference? Am I supposed to assume that because the scheme is TDM that I should not have a problem as there is time separation between send and receive? Does this P25 base station offer some DSP where it filters out signals that are received directly from the transmit antenna? Or do I have to rely on low power antennas with sufficient spatial separation?
I am new to the radio design field and not that well versed so any insight is greatly appreciated. Please let me know if my request is unclear and I will do my best to answer any system configuration questions.
Many Thanks!
I am working on an LMR radio project near the NYC area. The goal is to extent the two way radio coverage from an existing site via a hybrid DAS system to a large warehouse environment using GTR8000 base stations to generate the many simplex VHF frequencies for the client's LMR operations. On this antenna system we are also looking to pick up off-air first responded frequencies in the UHF/800MHz range. This means that the system will work with simplex and duplex frequencies. For the system to cater to all frequencies we have decided to combine all the TX frequencies (off-air TX and base stations TX) and all the RX frequencies. The TX frequencies will be transmitted throughout the warehouse via dedicated transmit antennas and the RX frequencies will be picked up via dedicated receive antennas. Since this site has many metal and concrete obstructions we have to place many antenna pairs(TX/RX) throughout the site. For the UHF/800MHz frequencies I am not so concerned as they are duplex but for the VHF I am worried that the transmit antennas will interfere with the receive antennas as they are receiving and transmitting on the same frequency. What are some ways to avoid this interference? Am I supposed to assume that because the scheme is TDM that I should not have a problem as there is time separation between send and receive? Does this P25 base station offer some DSP where it filters out signals that are received directly from the transmit antenna? Or do I have to rely on low power antennas with sufficient spatial separation?
I am new to the radio design field and not that well versed so any insight is greatly appreciated. Please let me know if my request is unclear and I will do my best to answer any system configuration questions.
Many Thanks!