Yes, Basic Electronics 101 (I passed that course in 1967, LOL) (God, I'm an old fart). I didn't bother to measure the DC resistance of the CAT5 because the thought didn't occur to me. By the way, there are also two "66" blocks in the loop (one at each end of the 25-pair trunk). Add in the resistance of anything else in the loop: two patch cables, four RJ45's, etc.
Just want to clarify: Power = VI, measured in watts - this is why VI = 19 above
When I had power issues in the past - I measured 4 Ohms resistance through 180FT of 24AWG, so 1200FT (600FT round trip) would be about 24 Ohms resistance.
Now, want to deliver 15W to power the equipment, but assuming 80% PSU efficiency, we actually need to transmit 15/0.8 = 19W.
V = IR, where V is the voltage drop across our 1200FT cable), R=24, and I, the current, depends on the voltage used by Vi2401 to transmit between the end points.
VI = 19 watts
V = IR (Ohm's Law)
so V = I *24,
so VI = I^2 * 24 (multiply both sides by I),
Now we know VI = 19 watts
so 19 = I^2 * 24
so I^2 = 19/24, I = sqrt(19/24) = 0.9 Amps current that needs to be transmitted across the cable
Now we can finally work out the voltage drop across the 1200FT (600FT loop) cable:
V_drop = IR = 0.9*24 = 22V voltage drop.
SO, IF the Vi2401 runs at 48+22 = 70V DC - all should be good!
Regarding getting great 100Mbps throughput across the single pair of UTP - this is easily achievable using VDSL2 modulation/data transmission schemes, which can achieve 100Mbps at 1600FT across phone cable (Cat5 >>> phone cable).
Undisclosed, we didn't intentionally run coax for our tests - it is already there. But neither did we use coax for the test. This was over a single pair of UTP. Vigitron provided the Vi2401's with modified baluns (tranformer jumpered out?) to convert UTP to BNC at each end for our testing. So 600' of a single pair of 24 gauge wire is transporting 100Mbps plus POE to power both the camera and the Vi2401 transmitter.
The point is, we don't have an IP infrastructure. All analog with ~50% coax and ~50% single-pair UTP using baluns and some active receivers. Converting to all-IP would be too costly and using 4 pairs per camera would require running a boatload of plenum UTP; also costly. And difficult, considering how overloaded and difficult to access our cable trays are.
Interesting solutions to connect ip camera www.sigrand.com <a href="http://www.sigrand.com">www.sigrand.com</a>, can connect the chain of cameras from one PoE switch port, maximum distance up to 500 meters. For distance of several kilometers can be used SHDSL extender or cameras with built-in SHDSL modem.
I haven't tried one, but Axis sells a T8129 POE extender for UTP. The coax solutions are typically for traditional analog CCTV to IP upgrades. Interesting to hear you intentionally ran COAX for the POE features.
Brian, Sorry, that was 100Mb/s (typo). Confirmed by running the camera in MJPEG mode, which was feeding ~22Mbps reliably. Obviously, 10Mb/s wouldn't handle that rate. The power draws are from factory specs, not via measurement. The Axis P3364 camera is feeding 720p @ 30fps with no loss of frames or resolution (bitrate capped at 4Mb/s in h.264). "Quality" is set at 70-80 and the camera is feeding around 3.5Mb/s on average with motion. We will also be testing the same transport with 1080p camera(s) in the future.
IPVMU Certified | 01/14/13 03:28pm
A few questions for you:
1) How are you measuring/confirming 100 Gb transport?
2) 'Supposedly 14.6 W' - Is this measured, or is it calculated from maxes?
Have you observed the quality of video from the camera? Is it running at full resolution/ high framerates?