use an isolation transformer? basic groundign questions...

gps isolation transformer 50 ohm

Hi all,

Our hardware is receiving a GPS 10Mhz sine wave signal (from a GPS receiver) via a 50 ohm BNC cable...

It looks like the shield of the BNC is on the receiver (that is transmitting the 10Mhz signal to us) is tied to chassis ground.

On our board that is receiving the GPS signal, our BNC is non-isolated (the body of the BNC is tied to the shield, which is tied to our chassis front panel ground) also the shield pin is tied to our logic ground.

This concerns me.. Granted the logic works, and we can recover the clock.. but

1) the exposed bnc shield is tied directly to our logic ground
2) our logic ground is now (through the BNC) tied to our chassis ground.

I was thinking of using a isolated BNC to break the logic/chassis ground connection, but that still leave the exposed BNC shield tied to our logic ground.

I am concerned about ground loops, and also ESD because we have a direct tie to our logic ground..

How can I tie this BNC connection to our board, provide a reference for the signal in the coax, yet still provide isolation for ESD and ground loops?.

Is it ok to have a direct connection to our logic ground like is currently implemented?

any help is appreciated..

thanks much!

-Bill

Re: use an isolation transformer? basic groundign questions.

The cheapest thing is to use two transformers (one at each end of the signal path.) and use a balanced type transmission line between the units. Shielded, twisted pair can be used. Ground the shield to the cabinet of the unit receiving the signal.

You can also use Optical Isolators. I've seen some Video Opto-isolators, which will cover the frequency band of intrest.