REV RPM Powered by CTRE VRM

Can I use the following path to power the radio? CTRE PDP → CTRE VRM → REV RPM → Radio

I haven’t been able to find rules explicitly allowing or prohibiting this, the closest is R616 and R617, but those don’t offer clarity. I am trying to maximize flexibility to mounting the radio high where it is accessible to field staff looking at it and have a tether on the practice field. My hope is that I can run just an ethernet cable up from the RPM and other electronics in the chassis, rather than extend the old REV passive POE injector wires up higher.

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I believe you technically can (edit: see @Peter_Johnson post below), but the middle part, VRMRPM, is a bit redundant and will also affect the input characteristics of the RPM. The RPM has lower minimum input voltage, which gives it a slight edge to preventing the radio from rebooting in extreme brownout conditions. Putting the RPM downstream of the VRM, the RPM will be dependent on the VRM’s minimum input voltage. I don’t know off hand how low the VRM can go before it completely shuts down, so this may not actually be a major issue. However, there are still efficiency losses by daisy chaining the regulators.

From an electrical standpoint I would recommend either of the following configurations:

  • PDPRPM → Radio
  • PDPVRM → POE Injector Cable → Radio

Hope that clears it up a bit!

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R617 makes it pretty clear that if you’re using the REV RPM to power the radio, you have to connect it directly to the PDP/PDH.

The device supplying power to the wireless bridge per R616 must be connected to either: [A] the designated supply terminals at the end of the PDP, as shown in Figure 9-14. … [B] the terminals of 1 of the non-switchable fused channels on the PDH.

R616 allows use of either a RPM or VRM to power the radio, not both.

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