I looked at the high resolution photos on the FCC site and didn't see
anything obvious. Now I've got the one I have on the bench out of the
case, I still don't see anything obvious heater-wise, but again I'm
not going to pop the shields off the board (requiring desoldering), to
be 100% sure...
On Thu, Jan 21, 2016 at 8:30 AM, Steve D <[email protected]
<mailto:[email protected]>> wrote:
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)
<[email protected] <mailto:[email protected]>> 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) <[email protected] <mailto:[email protected]>>
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 <[email protected]
<mailto:[email protected]>> 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**
***
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*Online: **www.surfici.net* <http://www.surfici.net>
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Tel: 406-449-3345 | Address: 3577 Countryside Road,
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[email protected] <mailto:[email protected]> |
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*Forrest Christian* /CEO//, PacketFlux Technologies, Inc./
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT
59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com <http://www.packetflux.com/>
<http://www.linkedin.com/in/fwchristian>
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--
*Forrest Christian* /CEO//, PacketFlux Technologies, Inc./
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com <http://www.packetflux.com/>
<http://www.linkedin.com/in/fwchristian>
<http://facebook.com/packetflux> <http://twitter.com/@packetflux>
