Wireless: Does the 2 channel Tempest base station provide redundant 2Tx transmission capability?
Question: I'm considering the purchase of a Tempest system, I would prefer to buy a 2 channel system to save some cost and it would be a better fit for the MS-702 in the church sanctuary, but I noticed that the 2 channel base station has only one antenna while the 4 channel base station has two antennas. What are the tradeoffs on RF performance between the 2 channel and 4 channel base stations? I will be mounting the base station in a rack in the equipment room, will I need to remote the antenna out of the equipment room to provide coverage in the sanctuary?
Answer: The diagram below shows the theory of operation for both the 4-channel (dual antenna) and 2-channel (single antenna) models of Tempest. The 2-channel model lacks some of the diversity characteristics found in the 4-channel model. For example, on Frequency 1 the Base Station and each Beltpack take turns broadcasting, each with its own time slot to send audio data (TDMA). The total time for one cycle is 5 milliseconds (1/200 second). The Base Station and all Beltpacks hop (FHSS) to a different predetermined frequency and the same audio data is sent again, but on a new frequency and on a different Base Station antenna (2xTX). Therefore, each receiver has two opportunities to receive the audio data. Duplicate data is discarded by the receiver and the process starts over with the next packet of audio data.
With 2xTX technology, each audio packet is transmitted twice, each on one of two consecutive hops. The loss of one packet transmission in a harsh RF environment is common. However, because of the quasi-orthogonal frequency relationship of the consecutive redundant packet transmission, the potential for loss of any single audio packet (2 consecutive data packet transmissions) is dramatically reduced. In addition, each packet transmission is sent out from different antennas. This unique approach enables Tempest to utilize spatial diversity, frequency diversity, time diversity and polarization diversity. The 2-channel product does not operate with spatial or polar diversity due to the fact it uses a single antenna during operation.
In order to regain the spatial and polar diversity aspects with the 2 channel base station the use of the CCT-RT remote antenna can be utilized via a CAT-5 cable. The remote transceiver has two antennas and works with either the 2 channel or 4 channel base. When the remote transceiver is plugged into the base the internal radio module in the base station is disabled.
Answer: The diagram below shows the theory of operation for both the 4-channel (dual antenna) and 2-channel (single antenna) models of Tempest. The 2-channel model lacks some of the diversity characteristics found in the 4-channel model. For example, on Frequency 1 the Base Station and each Beltpack take turns broadcasting, each with its own time slot to send audio data (TDMA). The total time for one cycle is 5 milliseconds (1/200 second). The Base Station and all Beltpacks hop (FHSS) to a different predetermined frequency and the same audio data is sent again, but on a new frequency and on a different Base Station antenna (2xTX). Therefore, each receiver has two opportunities to receive the audio data. Duplicate data is discarded by the receiver and the process starts over with the next packet of audio data.
With 2xTX technology, each audio packet is transmitted twice, each on one of two consecutive hops. The loss of one packet transmission in a harsh RF environment is common. However, because of the quasi-orthogonal frequency relationship of the consecutive redundant packet transmission, the potential for loss of any single audio packet (2 consecutive data packet transmissions) is dramatically reduced. In addition, each packet transmission is sent out from different antennas. This unique approach enables Tempest to utilize spatial diversity, frequency diversity, time diversity and polarization diversity. The 2-channel product does not operate with spatial or polar diversity due to the fact it uses a single antenna during operation.
In order to regain the spatial and polar diversity aspects with the 2 channel base station the use of the CCT-RT remote antenna can be utilized via a CAT-5 cable. The remote transceiver has two antennas and works with either the 2 channel or 4 channel base. When the remote transceiver is plugged into the base the internal radio module in the base station is disabled.
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