The thing to remember is that over a distance, voltage drops more at higher amperage operation than it does at low amperage operation. Wifi radio cards are constantly outputting at a wide range of amperage as it jumps back and forth between transmitting and not-transmitting. So to optimally protect your gear from over powering, you need to calculate the voltage drop it can have at the lowest current draw, which will have less voltage loss over the distance.
A good Voltage calculater is at: http://www.demarctech.com/techsupport/poecalculate.htm The most important thing to do is to make sure you use a "Regulated" power supply. A NON-regulated Supply could easilly have a 1-10 volts increase of voltage above spec when not under load. Its important to know that all Metro boards do not have the same MAX voltage rating. You might not be able to know for sure that your Metro can support up to 48V without first looking at imprint on the SBC listing such. The other issue is considering the impact that a electrical AC power surge will have on the DC power that goes to the SBC. If you have a cheap PS it may allow higher voltage up the wire. A good quality hi watt regulated PS will absorb the surge into its capacitors, to protect the SBC. It may work, but I'd argue you'd be taking an unnecessary risk. >I have ran the board on the same 48v power supply on the bench and it > ran fine If the Metro board is on your bench, is it labeled a max voltage? The 48V model Metros handled significantly more (I thought 56V) But not sure on the 24V model metros. Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Kurt Fankhauser" <[EMAIL PROTECTED]> To: "'WISPA General List'" <wireless@wispa.org> Sent: Thursday, September 11, 2008 4:27 PM Subject: [WISPA] 24v Metro max input voltage? >I was working on a water tower today and I have a new 24v model WAR-METRO >at > the top. I have not powered it yet but it will be on about 225 foot of 24 > gauge CAT5. My question is does anyone know what the max input voltage is > on > these things? Wlanparts.com lists it as 24v-48v input and I was trying to > search the STAR-OS forums and Lonnie I think mentioned 48v is the absolute > max and that 48.1v will start damaging the board. I have a 48v power > supply > bought from RFLINX in hand that I would like to use. If my calculations > are > right by the time the voltage gets up the Ethernet at this footage it will > be outputting around 46-47 volts so it should not damage the board at that > range. I have ran the board on the same 48v power supply on the bench and > it > ran fine for the few minutes it was plugged in. > > > > Looking for comments from anyone that may have ran a 24v METRO board on > 48v > POE or similar. > > > > Kurt Fankhauser > WAVELINC > P.O. Box 126 > Bucyrus, OH 44820 > 419-562-6405 > www.wavelinc.com > > > > > > > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
