Looks like inductive flyback/kickback. Be fun to put a small cap in parallel with the output. I’ll bet you can tune it out.
From: Forrest Christian (List Account) Sent: Monday, November 09, 2015 4:20 PM To: af Subject: Re: [AFMUG] SyncInjectors and PMP450i Sort of. First of all, a normal pulse out of a syncinjector into a short cable: Interesting things happen when you shoot this into a long cable: Those bounces at the front are my best guess as to what is causing the 450i to not like the sync pulse. That's on a 100m cable, and those pulses are most likely caused by the signal bouncing off the end of the cable and back and/or some different interaction with a long CAT5 cable. It should be noted that similar bounces also happen with the 100 and the 450, and even with official cambium sync sources (aka the CMM Micro), but the software in those radios seem to ignore the stray pulses, only paying attention to the final edge. Not so with the 450i. It just refuses to play. The new I0 injectors turn the power off a bit more smoothly, making the bounce not exist, even on a long cable: On Mon, Nov 9, 2015 at 4:02 PM, George Skorup <[email protected]> wrote: Let me guess, they only take a CMM4 aligned pulse? On 11/9/2015 4:21 PM, Forrest Christian (List Account) wrote: 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 [email protected] and we will work with you to ensure you have hardware which will work with your hardware. -- Forrest Christian CEO, PacketFlux Technologies, Inc. Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 [email protected] | http://www.packetflux.com -- Forrest Christian CEO, PacketFlux Technologies, Inc. Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 [email protected] | http://www.packetflux.com
