PTP 650 DC supply reference


If I am using a dc supply via the enhanced ac + dc power injector,  can the dc supply be referenced to the chassis of the radio?

If we call the dc supply connections 0V and +48Vdc, is it ok if I connect 0v to the chassis of the radio?

It appears to me that 0V on the enhanced ac and dc power injector is floating relative to the radio chassis and so I assume that this is ok but I would like verification.  (Maybe there is a dc/dc converter inside PTP 650?)

I'm using a metal battery box which houses the PTP 650.  Surge suppressors are used so the coax screen, antenna mount and radio chassis are connected to the battery box chassis from a dc resistance perspective.  Can I internally reference my DC supply to the battery box chassis too or should I keep it isolated (thus floating relative to the radio)?

Thanks for any advice.

Hello David, You are correct, there is an isolated DC-DC converter inside the radio which allows the freedom to use floating or referenced power systems. If an external floating supply is used the 0V input must not exceed 100V with respect to the chassis otherwise surge protection devices in the radio will start to clamp.

There is advantage in keeping the supplies isolated. Drop cable wiring and plugs which contact the mast or other grounded metalwork will not suffer potentially destructive short circuit currents. These could be caused by current flowing from the battery positive (negative ground system) through the power injector, though the cabling then through a ground short back to the battery. A similar risk exists for positive ground systems.

When using an external supply, especially a battery, it is imperative that fusing is placed in the supply lines to protect against wiring damage.

Regards, Tim


Thanks for that explanation Tim!

It's nice to have conformation of the reality.

Everthing is suitably fused, thank you.

Have a great weekend.