The nice thing about this method is that it's all passive components.
I might still rather do the switch at top with PoE in+out and VLAN per
SM. Without actually adding everything up I'd wager that the cost was
about the same....or comparable at least. The operational difference is
in whether you have more faith in the brains out in the field or more
faith in the brains in the office configuring switches. And if the
building had more than 2 units it might matter that you can add a 3rd or
4th SM this way.
Or the ultimate lesson to take away from this: If you're running a
difficult and time consuming cable path then pull extra cables at the
same time. It's hard to get employees to look past the current job and
think about how they can help themselves in the future, but it's nice if
they can.
On 1/29/2020 12:52 AM, Forrest Christian (List Account) wrote:
The differing twist lengths are engineered to minimize crosstalk
between the pairs. If all of them have the same number of twists per
inch then you will find that the same wires tend to be next to each
other down the length of the cable. If instead you have each of them
have a different number of twists such that over the length of the
cable the amount of time each is in contact with each other tends to
be more even, reducing crosstalk.
I suspect in some cases having two separate links running through the
same cable will hurt performance because you will get crosstalk from
the other link which you may not be able to cancel out using an echo
canceller. Probably depends on the length and specifics of the link.
On Tue, Jan 28, 2020 at 8:33 PM Ken Hohhof <af...@kwisp.com
<mailto:af...@kwisp.com>> wrote:
Each pair has a different number of twists per inch. In Cat5 and
Cat5e cable I observe the green and orange pairs, which are the
data pairs, have the tightest twists. I don’t remember if Cat6 is
similar. This leads me to believe the blue and brown pairs may
have inferior crosstalk performance. But GigE uses all 4 pairs
for data, so my theory is probably wrong. I guess the important
thing is that none of the pairs have the same number of twists.
The reason I mention this is sometimes I see people assert that if
you split a Cat5 cable into 2 as is being discussed, it will hurt
the performance.
*From:* AF <af-boun...@af.afmug.com
<mailto:af-boun...@af.afmug.com>> *On Behalf Of *Forrest Christian
(List Account)
*Sent:* Tuesday, January 28, 2020 5:24 PM
*To:* AnimalFarm Microwave Users Group <af@af.afmug.com
<mailto:af@af.afmug.com>>
*Subject:* Re: [AFMUG] Cambium POE Splitter
This is actually pretty simple:
Split the CAT5 into two, two pairs per radio, put the pairs on the
data line. At the bottom use a 24V gigabit capable injector which
puts the power on the data pairs. We have a couple at PacketFlux,
Chuck makes a couple, and there are others available. The goal
here is to get the 24V riding the data line along with the data.
So effectively you have two 10/100 capable links up with power
on them.
At the top, you reverse the process.... get a device which will
pull the power off of the data pairs, probably one of them from
Chuck. (See 800-GigE-PoE as an example). Plug the cable from
the bottom in the PoE port, then build yourself a cable for the
radio which puts the extracted power on 4,5,7,8 and the data pins
where they belong.
You could also use a single midspan Gigabit PoE injector at the
bottom with power on all 4 pairs, then remove it using a similar
one at the top. Then your long CAT5 stays unsplit, and the
splitting and PoE mess is all in a single cable harness. To do
this you'd take two cat5 cables, and then wire the 1,2,3,6 pairs
from each cable into a single RJ45 (putting one on 1,2,3,6 and the
other on 4,5,7,8) which gets plugged into the non-PoE side of the
extractor. Then the remaining 4,5,7,8 wires you'd connect to the
power which came out of the PoE extractor at the top. The
bottom harness would be similar but for simplicity you can just
put 24V in the injector and not connect 4,5,7,8 on either CAT5.
Now I think about this, this is what I'd probably do and just use
a single 800-GigE-PoE top and bottom.
On Tue, Jan 28, 2020 at 9:17 AM Matt <matt.mailingli...@gmail.com
<mailto:matt.mailingli...@gmail.com>> wrote:
I have a case where I need to power up two separate Cambium 24
volt
SMs on rooftop but only need 100base to each. Its very
difficult to
run the second wire at this location which I need. Anyone know
of way
to split the cat5 at bottom and top to do this? Not likely but
thought I would ask.
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