ptp650 gigabit ethernet problem with LPU


I have 2 ptp650 on same pole. This pole its on the top of a mountain, so there are zero radio interferences. Because there are the only device on this pole, I have connected directly the 2 PIDU with a 30 cm utp cat6 patch cable.

This is the configuration:

PTP650-----LPU-----Cambium Cable (3 meters)------LPU------Cambium Cable (1 meter)------PIDU----Patch utp cat6 (30 cm)----PIDU-----Cambium Cable (3 meters)------LPU-----PTP650

The LPU model is: C000065L007A


Problem: in this configuration, the 2 "main PSU port speed" run at 100 Mbps Full Duplex.

I have substituted all devices (cable, connectors, PIDU, LPU, ptp650) but th eproblem persist.

If I remove the 2 (lower) LPU the port speed became 1000 Mbps Full duplex.


Because in this place there are a lot lightning and i must go to gigabit, I must resolve this problem. Any suggestion?

I see the same problem in differents tower, but right now I thinked that its caused by FM 300 mhz interferece. This situation show me that probably the LPU interfer with gigabit ethernet. How its possible?



Hi Pierre,

I'm assuming that your installation has four LPUs. Is that right?

1000BASE-T Ethernet does not cope well with loading or mismatch on the cable. A standard installation with a PIDU and two LPUs will work up to 100 m. The direct connection that you have used here almost never works, and we warn against this in the PTP 650 User Guide. The total loading of four LPUs and two PIDUs is more than the Ethernet transceivers in the PTP 650 (or any other network equipment) can handle.

The obvious solution is to install a simple Ethernet switch between the two PIDUs. This will regenerate the Ethernet signal, so that each circuit sees only two LPUs and one PIDU.

If that solution is not possible, you might want to remove the two lower LPUs. You've already demonstrated that this connects at 1000 Mbit/s. There will be some increased risk of lightning damage, and it's difficult for us to quantify the increased risk in your installation. If the area has a lot of lightning activity, the risk is obviously higher.


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