Other radio performance considerations
Influence of the antenna height on range
There are many options to set up the radio antennas. They can be assembled directly on the GNSS receiver, be placed on a tripod mount, or mounted on top of a 1.82 m (6 ft) fiberglass mast. The antenna gain can also be set to either 1 db or 5 db.
When all other parameters are kept constant:
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increasing the transmitter (Tx) antenna height from 2 m to 3 m increases the range by about 15%. This can be achieved by using the tripod side mount kit with extension pole.
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increasing the Tx antenna height from 2 m to 4 m increases the range by 30%. This can be achieved by using the radio antenna mast – telescopic.
It is important to consider the placement of the antenna in relation to the rover receiver. Avoid all obstacles that block or deflect the radio signals, such as buildings and power lines.
Influence of the baud rate on range
Trimble recommends using the TRIMTALK v1 protocol on 400 MHz band radios. The baud rate setting negatively affects the range, while only marginally increasing the throughput. Please note that not all settings are available in all countries to comply with local regulations.
TRIMTALK v1 @ 4800 bauds have 20% longer range than 9600 bauds and 40% to 50% longer range than 16000 bauds or higher. However, the latter two options only provide 700 bytes/epoch throughput compared with 516 bytes/epoch for 4800 bauds
Input voltage for external radios
12 V batteries output 13.8 V when in good condition and fully charged. Older or partially discharged batteries output much lower voltages. At these lower voltages, the radio has a shorter range. Long power cables, worn out cables, and corroded connectors all contribute to lowering the input voltage and should be avoided.
Cable lengths and connectors
Keep the coaxial cables from the radio to the antenna as short as possible. Cable and antenna connectors are a source of signal loss. Keep them clean and change both cables and antennas if there are any visible signs of wear. Any rotation, play, wear, and/or corrosion on the central pin of these connectors is a sign that it needs replacing. This last point also applies to the TNC connector on the radio. This is the reason why the radio is shipped with a TNC-to-TNC adapter. If you frequently connect and disconnect the antenna or antenna cable, Trimble recommends using this adapter to avoid the need to replace the TDL450B TNC antenna connector.
Influence of radio power on range
Currently, Trimble GNSS receivers are built with an optional 1 or 2 W 400 MHz band UHF internal radio. The TDL450B radio has a 35 W maximum power output although this can be limited by your license.
When all other parameters are kept constant, increasing from 1 W to 24 W approximately doubles the range.
The theoretical range reduction from 35 W to 20 W transmission is about 15%. There are many advantages of using 20 W versus 35 W such as battery life and the ability to work in higher ambient temperatures.
Higher ambient temperature configurations
The TDL450B radio, like any high-power UHF radio, generates heat. The heat sink at the back of the radio is designed to cool down the radio. In high ambient temperature environments, the capacity of the heat sink to keep the radio electronics at a level that prevents damage or excessive wear becomes a limiting factor in the radio performance.
The radio has internal embedded processes that automatically reduce the transmission power when it reaches these critical temperatures. The reduced transmission power reduces the range at which the broadcast can be received correctly. When this occurs, the radio raises an alarm so that you can take appropriate action for future broadcasts.
The first recommendation when working in high ambient temperature environments is to ensure good ventilation of the heat sink. The Fan tray (P/N 129681-20), by generating forced air flow over the heat sink, greatly helps in keeping the radio under the critical temperatures. However, the amount of heat generated by the radio also highly depends on its configuration. Some configurations cause the radio’s transmitter to stay on for longer periods, and the longer the radio is actually transmitting, the more heat it generates. Reducing the size of the data you are transmitting by using a compact format, such as CMRx, or the number of satellite corrections you are broadcasting helps reduce the transmission time. Reducing the transmission power also reduces the heat generated by the radio. Trimble recommends setting the transmission power to the level actually required for the needed range, especially in high ambient temperature environments. You can compensate the loss of range with a higher gain antenna or place the antenna higher above the ground and away from any objects that could blocks its signal.
