The GPS connector on the DM4601e has got juice on it

[Q] I have one question about GPS connector on DM4601e radio and could not find the answer. Is the GPS connection on the DM4601e active ( voltage out to active GPS antenna)? If yes, what voltage is it?

[A] Yes, the GPS antenna is active. The radio provides 5VDC on the SMA connector for this purpose. This voltage is needed to power the GNSS antenna.

The reason for this is that the radio could be mounted anywhere in the vehicle often with no visibility of the sky. To get GPS (GNSS) signal, an external antenna must be used.

The problem then is, the GNSS signal is at 1,575GHz and most coaxial cable will have tremendous losses at this frequency. For example, the RG174 used with the above PMAN4001A antenna has about 9dB loss.

To overcome this loss, GNSS antennas have a built-in low noise amplifier as well as a band-pass filter to prevent desense from the transmitter. The 5V DC supply is superimposed onto the coaxial cable from the radio end.

I guess the important thing to remember is to make sure there are no shorts or breaks on this cable when doing/fixing an installation.