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When building a coax cable to go between a GPS antenna and receiver, keep the total loss less than 10 dB. The type of coax cable you use will determine the maximum lenth that you can go. Don't forget that every connector you use will also add some amount of loss.
Here are some approximate maximum lengths for several common types of coax:
RG-58 = 50 feet max
LMR-195 = 60 feet max
LMR-240 = 100 feet max
LMR-400 = 200 feet max
There are numerous coax cable signal loss calculators online that will show you how much dB loss there is for a specified length. Set the line length to whatever you need, use a frequency of 1500 MHz, and power of 1 watt.
Coax loss calculator 1
Coax loss calculator 2
For dual-antenna receivers such as the NovAtel PwrPak7D, the coax cables do not need to be the same lenght.
Last updated: February 12, 2021