GPS and GNSS antenna installations are very sensitive to cable type and cable length. A coax cable of 50 ohm impendence and able to handle frequencies of at least 1.5 GHz should be used. The cable should also be matched with 50 ohm RF connectors, such as TNC and N-types.
LMR type cables, such as LMR195 and LMR400, are well suited to GNSS antenna installations.
The factors which determine maximum cable distance are:
- The gain (or amplification) of the antenna.
- The attenuation of the cable.
The gain of the TW3040 antenna, supplied with the TA-Series, is 40dB. The attenuation of LMR195 type cable is 0.48 dB/m at 1500 MHz. The GNSS receiver used in the TA-Series requires at least 10dB of gain at its input.
Therefore, the maximum LMR195 cable length is (40 – 10) / 0.48 = 62m.
The attenuation of LMR400 type cable is 0.17 dB/m at 1500 MHz.
Therefore, the maximum LMR400 cable length is (40 – 10) / 0.17 = 176m.
The gain of the optional TW3152 antenna is at least 48 dB minimum.
Therefore, the maximum LMR195 type cable length is (48 – 10) / 0.48 = 79m.
The maximum LMR400 type cable length is (48 – 10) / 0.17 = 223m.
Supplied Cables
TimeTools provides a range of coax cables tailored to GPS/GNSS installations.
Product Code: TCX-20S
20m length LLA195 low-loss coax cable tailored for TA-Series NTP server and antenna installations. Supplied as 5m TNC-plug to N-jack and 15m N-plug to TNC-plug, for installation of an optional surge suppressor. The TCX-20S cable is provided in the standard TA-Series NTP server package.
Product Code: TCX-30S
30m length LLA195 low-loss coax cable tailored for TA-Series NTP server and antenna installations. Supplied as 5m TNC-plug to N-jack and 25m N-plug to TNC-plug, for installation of an optional surge suppressor.
Product Code: TCX-50S
50m length LLA195 low-loss coax cable tailored for TA-Series NTP server and antenna installations. Supplied as 5m TNC-plug to N-jack and 45m N-plug to TNC-plug, for installation of an optional surge suppressor.
TimeTools can provide customised antenna cables, up to 200m in length, to accommodate specific installation requirements.
For extremely long cable runs, GPS/GNSS over fiber equipment can be used to transmit GNSS signals over optical fiber cable.