I believe Phihong wired it that way so that you can use it as a 3at
compliant injector where only two pairs may be present (so 10/100 only).
IP phones come to mind. We run into a lot of older-ish structured wiring
where they ran only one cat5 and stole one pair for phone and two pairs
for ethernet. Not the way I'd do it, but whatever. Most of the phones
we're using now have a built-in GigE switch.
I remember seeing in the 450i guide that it will take either polarity on
all pairs. If you're not using the aux port, then two pairs for power
(30W) will be fine. If you are, or I suppose if it's a long run, then
all four pairs for power would be warranted. I really like this PoE
design. Would be nice if the regular 450 APs would take 48-56VDC. I know
they talked about that at one point, but it looks like we're limited to
30VDC. Well, at least that's what the label says.
The whole pin swapping thing with the 450i and CMM4 is because 56VDC
mode on the CMM4 is wired for the split pair 320/430 config. With the AP
being pair polarity agnostic, you don't need to do the swapping when
using a SyncInjector. Basically it will take the standard Canopy POE
pinout, just needs to be >=48VDC. Probably more like >40VDC.
On 1/4/2016 12:50 PM, Ken Hohhof wrote:
Good point about the power being on 1/2 and 3/6. I guess that makes
it 802.3at Alternative A wiring. According to the schematic, 4/5 and
7/8 are wired straight through with no transformer. So gigabit
compatible with only 2 transformers. Probably for non gigabit
compatible, Alternative B is cheaper because you don’t need any
transformers at all. And the 60-75 watt POEs use all 8 wires for data
and power, so 4 transformers.
So confusing!
I can’t find any wiring diagrams for the Cambium N000065L001B, but at
60 watts, I guess it must use all 8 wires for power. Hence the price?
Something else I notice is the Cambium POE is rated for 0 to 40C,
while the Phihong unit is rated –20 to +65C. Cambium tells you to use
a PIDU for non controlled environment. Or Netonix or GIGE-POE-APC or
Syncinjector.
Still, AC powered POEs are handy for configuring radios on the bench,
or like that case where I needed a POE at a customer’s office to power
a SIP paging amplifier.
*From:* George Skorup <mailto:geo...@cbcast.com>
*Sent:* Monday, January 04, 2016 2:35 AM
*To:* af@afmug.com <mailto:af@afmug.com>
*Subject:* Re: [AFMUG] 802.3at POEs
It's cheaper at Allied:
http://www.alliedelec.com/phihong-poe36u-1at-r/70124112/
Yeah, if you're not going to use the Aux port on the 450i, there's no
reason to buy a 60W injector. Just keep in mind that this Phihong
injector is power over the 10/100 data lines. And is - on 1&2, + on
3&6. It'll work perfectly fine with the 450i APs and 5GHz SMs. And
obviously the Exalt ExtendAir G2. The 450i is awesome with the any
pair power setup.
The one thing I will say about this thing is that it runs a bit hot
and if your hearing is decent, you can definitely hear the switcher
whining away.
On 1/3/2016 7:29 PM, Ken Hohhof wrote:
I'm getting more and more equipment with 802.3at POEs, and I feel
like I'm getting raped on the price if I get the POE from the
equipment vendor. High price and minimal features.
My Exalt G2 radios came with these really nice POEs that have
diagnostic LEDs and tabs for wall mounting as well as rubber feet for
desktop use. The only downside is they are kind of big, but that's
not necessarily bad, that may help prevent overheating. It has LED
indications for valid 802.3af and 802.3at signatures, as well as a
flashing overload indication.
I looked up the part number, expecting them to be expensive, but
Digi-Key has a bunch of them in stock and the price is quite
reasonable ($38 in single quantity).
http://www.digikey.com/product-detail/en/POE36U-1AT/993-1088-ND/2384576
From the picture, this is also the POE that I should have gotten from
CyberData to go with the SIP paging amplifier I bought, but instead
they sent a cheaper L-Com POE that has just one dumb LED to show it
is getting AC power. So I paid something like $64 for a $31 POE.
The $100 Cambium POE for 450i is probably more than 36 watts in case
you want to use the AUX port on the AP, but it lacks the nice
mounting tabs and diagnostic LEDs. And 36 watts should be more than
enough to power just the AP.
So I’m inclined to just buy a bunch of the nice Phihong units and use
them on everything. Am I missing something?
