I do want to clarify one item: This is not necessarily related to the cambium DRAM issue. I don't want to claim that problem, since this isn't the same thing. This is more of an issue where you have ePMP's which seem to start having power-related issues. If moving to a 30V brick makes your problem go away, then the issue I describe below probably is your issue. If moving to a higher voltage doesn't fix the issue then this probably doesn't relate to your issue. Regardless, it is my intent to recommend that my customers move to 48V as soon as I confirm that this seems to fix at least a decent number of the problems without causing others.
Unfortunately this might be a case of the cold weather aggravating two separate issues (or for that matter, the cold weather causing increased current consumption in the ePMP, which then requires a higher voltage to operate correctly). -forrest On Thu, Jan 21, 2016 at 12:43 AM, Forrest Christian (List Account) < li...@packetflux.com> wrote: > A bit of an update from the PacketFlux side. > > Late this afternoon I received a ticket from Tyson in relation to these > issues. In particular, sync from a PacketFlux SyncInjector dropping off on > an ePMP when it's cold. I have spent a bit of time this evening > investigating this issue. The following is a summary of what I found. > It's a bit long-winded so that those experiencing the problems can > understand my current working theory and help me figure out if this is the > case. > > WARNING: The following is based on a limited amount of testing with a > single ePMP with no traffic and no clients and on a bench. This is likely > the best case scenario. The field is only going to be worse. > > The setup is as follows: > > ePMP 1000 GPS AP, with no GPS hockey puck attached, connected to a Gigabit > Syncinjector (Rev H and Rev I - I have a special one with a port of each > 'type' ;-) ). I am powering the injector with a variable power supply so > I can vary the voltages in. The AP is connected to the Injector with ~100m > of CAT5 cable. The Antenna connectors have terminators on them, the AP is > in transmit mode, but isn't passing any traffic since there are no clients. > > When feeding the injector with 24V, I get about 23V at the AP. This is > pretty consistent with what I would expect in this situation. The AP > seems to work fine, at least on the bench and without doing any real > work. However, as the voltage drops, things start to get weird: > > At around 22V in, (21V at the AP), Sync becomes flaky. This is consistent > on both H and I version ports on the injector. Sometimes it works, > sometimes it doesn't. Note that 22V is the bottom of the rated voltage > inputs for the ePMP. > > At around 20.5V in (19.5V at the AP), the radio just turns off. It won't > turn back on until around 22V. > > Now here's where some total speculation comes to play. On the bench, > this unit is drawing around 3W. Let's assume that under load, and when > temperatures are cold, this unit draws closer to 6W. This would double the > current, and quadruple the voltage drop. Now, assume 24V in, this puts you > at around 20V in at the AP, which is about the turnoff point. Remember > this is on 100m of wire, and a total speculation about a the power draw of > a cold, under load AP. But the point is valid, regardless of the cause - > if the circuit resistance when combined with the power load causes a low > enough voltage at the AP, weird things will happen. And since weird things > seem to start to happen around 22V, there just isn't much headroom at > 24V. > > This explains why things work well at 30V. > > For those who are having this problem I'd recommend trying increasing the > voltage into the SyncInjector. The Revision H injectors can safely handle > up to around 56V or so. Assuming all of the radios on an injector are > either ePMP or the newer 450i's, using 56V into a SyncInjector is perfectly > acceptable and the ePMP's are rated up to 56V as well. > > So the summary: Try a 48VDC voltage source instead of 24V and see what > happens. > > -forrest > > > > > > > > > > > > > On Wed, Jan 20, 2016 at 11:00 AM, Tyson Burris @ Internet Communications > Inc <t...@franklinisp.net> wrote: > >> Hello Cambium, >> >> >> >> At the MidWest-IX launch party last night, several of us Indiana WISPs >> compared notes on the ‘cold weather’ problems we are seeing with ePMPs. It >> was very interesting to learn we are experience identical problems across >> the spectrum. >> >> We all understand this is a DRAM issue with certain units you have >> identified. We also understand the firmware RC that has been made >> available to fix this short term. >> >> The bottom line is we are very frustrated and grow tired of dealing with >> it. >> >> >> >> Our concern is simple. If your software fix ‘degrades’ the performance >> of the product or triggers other issues, as it has been suggested, we would >> prefer a full recall and replacement program immediately. >> >> >> >> If the suggestion that the fix will degrade the product performance is >> inaccurate and not cause other issues, I would like for this to be made >> public. >> >> >> >> Thank you, >> >> >> >> *Tyson Burris, President* >> *Internet Communications Inc.* >> *739 Commerce Dr.* >> *Franklin, IN 46131* >> >> *317-738-0320 <317-738-0320> Daytime #* >> *317-412-1540 <317-412-1540> Cell/Direct #* >> *Online: **www.surfici.net* <http://www.surfici.net> >> >> >> >> [image: ICI] >> >> *What can ICI do for you?* >> >> >> *Broadband Wireless - PtP/PtMP Solutions - WiMax - Mesh Wifi/Hotzones - >> IP Security - Fiber - Tower - Infrastructure.* >> >> *CONFIDENTIALITY NOTICE: This e-mail is intended for the* >> *addressee shown. It contains information that is* >> *confidential and protected from disclosure. Any review,* >> *dissemination or use of this transmission or its contents by* >> *unauthorized organizations or individuals is strictly* >> *prohibited.* >> >> >> > > > > -- > *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* > Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 > forre...@imach.com | http://www.packetflux.com > <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> > <http://twitter.com/@packetflux> > > -- *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 forre...@imach.com | http://www.packetflux.com <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> <http://twitter.com/@packetflux>
