Trangos did.
From: Steve D
Sent: Thursday, January 21, 2016 8:30 AM
To: af
Subject: Re: [AFMUG] To Cambium With Love - Replace the bad ePMP units.
Just throwing this out there, but don't the epmp's have a small heater in them
that could be turning on when it's cold, drawing additional power? I recall it
was supposed to pre-heat components to avoid freezeup on first boot but I can't
recall if that's the only time they run or not.
-Steve D
On Thu, Jan 21, 2016 at 1:44 AM, Forrest Christian (List Account)
<li...@packetflux.com> wrote:
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 Daytime #
317-412-1540 Cell/Direct #
Online: www.surfici.net
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,
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--
Forrest Christian CEO, PacketFlux Technologies, Inc.
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
forre...@imach.com | http://www.packetflux.com
--
Forrest Christian CEO, PacketFlux Technologies, Inc.
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
forre...@imach.com | http://www.packetflux.com
