I’m evaluating the purchase of an RTK reference station (e.g., Mosaic-X5) and noticed that the default cable length provided is 10 meters. However, for my intended setup, I would require a cable of approximately 20 meters.
My question is:
What is the maximum cable length allowed between the antenna and the reference station without compromising performance?
Can the default 10m cable be replaced with a 20m cable, and if so, are there any specific considerations or recommendations for the cable type?
Thanks in advance for your insights!
You should be fine. I recommend you add a RG58 10m extension to the included cable in the kit. Avoid the thinner RG174 if you can.
For the SparkFun RTK product videos I shoot, I regularly have to hook up 3 x RG58 10m extensions + 1 x RG174 extension (so 40m total) to an antenna on our roof with some degradation to the signal, but not much. The GNSS receiver doesn’t care. I may loose a few very low signal satellites but they are of so low elevation the receiver is likely already ignoring them in the solutions.
It is measuring the time/location of the signals incident on the antenna’s phase-center. The cable just adds delay commensurate with length vs Speed-of-light (SoL). ie these signals chase down the cable effectively at a uniform speed, irrespective of the distance between the antenna and the satellite.
The time the recevier thinks it is will be slightly distorted, so 1PPS output, and this perhaps can be compensated via a setting, but doesn’t impact the observations, and their time, as correcting and deriving a common instant in time is part of solving GNSS and RTK.
Hundreds of feet, up a tower, consider LMR-400, probably unmanagable due to rigidty in most applications. At 10-20 metres some RG6Q, 3 GHz swept satellite TV cable would be quite servicable and probably easier to run thru a building, and crimp connectors.
If you are in Europe, I can recommend Messi & Paoloni Ultraflex 7 cable. The attenuation at 1.3GHz is around 2.2dB per 10m. The connectors are bulky and the central pin needs to be hand-soldered, but they are very robust. Regular RG58 will attenuate by around 6dB per 10m.