Syncinjectors and PMP450i

This was posted to the AFMUG mailing list from Forrest at Packetflux. Applies to folks with PMP450i and SyncInjectors.

We have recently become aware of a potential issue when using a SyncInjector with a PMP450i. The short version of this issue is that with certain cable runs (mostly longer ones), a PMP450i will refuse to accept the sync from the SyncInjector as valid, even though the pulse is perfectly valid and should be accepted by the PMP450i.

Currently, there are two ways this can be fixed. Since the pulse is valid, but just not recognized as valid by the currently shipping PMP450i firmware, Cambium could fix this in software. I believe they are currently investigating this as an issue, and I honestly expect them to release a fix assuming it isn’t a major issue to do so. If this happens, it should address all of the existing SyncInjectors in the field which our customers may want to use in the future with a a PMP450i.

The second way to fix this issue is for us to modify our sync pulse slightly so that it is in line with what the PMP450i is expecting. Because this modification has some additional benefits beyond better interoperability with the current PMP450i firmware (such as the modified pulse being less likely to induct noise into adjoining cables), we have decided to proceed down this path as well.

During the next week or so, we will begin shipping Revision I0 of our Gigabit SyncInjector Product. The first of these are currently working their way through our assembly line. This version contains improved support for voltages above 58V and also the waveform modification mentioned above. It should be functionally identical to the earlier Revision H0 SyncInjectors. It is not our intention to update our non-gigabit injectors at this time.

If you are currently having problems with sync over power on a Gigabit SyncInjector and a PMP450i, please send an email into and we will work with you to ensure you have hardware which will work with your hardware.