Frequently Asked Question
Absolute safe maximum we calculated (not measured) with H155 coax cable, GNSS module and 38dB gain antenna is 80m, but may work up to 118m. For everything above 80m we suggest using (eg. inline) extra GNSS amplifier (introduces additional delay for GNSS signal).
Calculation for anyone:
{[(y - x) + z) - 7dB] / g} * 100
- x - antenna module sensitivity (-143dBm for standard NTS-Pico3)
- y - satellite GNSS signal on earth (about -130dBm, but with clear weather)
- z - antenna gain (in our past product is was AT BEST +38dB, active antenna has built-in amplifier)
- g - cable attenuation per 100m (~37dB/100m at 1575MHz for H155 coax cable)
Example for NTS-Pico:
{[(-130 - (-143)) + 38 - 7] / 37} * 100 ~= 118m
Note that this value of 118m is theoretical in perfect environment.
You may find any components and input values into this calculation, we used standard values from NTS-Pico3 brochure from 24.03.2022.
Useful links:
https://www.gpssource.com/collections/splitters
https://www.instockwireless.com/gps-antenna-signal-splitter-gps210.htm
http://gpsinformation.net/main/gpspower.htm
Examples:
Standard shipped NTS-Pico antenna has 38dB gain (built-in signal amplifier).
H155 => 0.42dB/m @ 1.7GHz
If for any reason this will not satisfy your client or he requests longer distance we definitely recommend to use H1000. H1000 => 0.213dB/m @ 1.7GHz or LMR-400 (0.186dB/m @ 1.8GHz).
Typical cables:
| coax cable | attenuation [dB / m, dB/100m @ frequency near/above GNSS band] |
| LMR-195 | 0.421...0.477 dB/m @ 1.5GHz |
| RG58 | 0.476 dB/m @ 1.5GHz |
| H155 | 0.423 dB/m @ 1.7GHz, ~37dB/100m @ 1.575GHz |
| H1000 (rigid / semi-rigid) | 0.213 dB/m @ 1.75GHz |
| LMR-400 | 0.186dB/m @ 1.8GHz |
Example of calculation for GPS signal:
| cable attenuation around GNSS band(s) | 48dB/100m (minus skipped here yet) |
| Attenuation of the cable | for 30m: -14.4dB, for 50m -24dB |
| GPS L1 signal strength at face of the earth | -130dBm |
| Passive antenna gain | ~0dB or ~0dBi |
| Standard Pico3 active antenna amplifier gain | ~ +38dB in GNSS L1 band |
| Receiver sensitivity for cold start | -143dBm (old hardware version of NTS-Pico3) -148dBm (newer hardware version of NTS-Pico3, but requires -136dBm for Galileo, -130dBm for SBAS) |
| Assumed margin for connectors etc. | 2...4...6dB or even 7dB (attenuation, so negative value) |
For 50m of the cable:
-130dBm +0dB +38dB -24dB -7dB = -123dBm which is above required absolute minimum -143dBm for the receiver - GNSS receiver with the cable should synchronize to GPS signal if antenna mounted properly (eg. full sky view, no reflections, no RF interferences at GNSS band which greatly reduces Signal-To-Noise ratio).
Yet another approach:
Active antenna should not be worse than passive antenna, ie. +38dB -24dB -7dB = +7dB which is still above +0dB for passive antenna.