ALIX.2D2 - How many high powered wi-fi cards can I use?
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All,
I have an ALIX.2D2 currently with an ALFA AWUS036H USB wireless card and a single CM9 mini-pci card. I would like to expand to a total of two AWUS036H USB wireless cards and a high powered mini-pci 802.11 wireless card. This would give me a total of:
2 x ALFA AWUS036H USB (radio output is 1W each and the device requires 5V)
1 x CM9 mini-pci wireless card (radio output is 63mW)
1 x high powered mini-pci wireless card (radio output is 700mW)My concern is if the ALIX board will be overloaded.
The ALIX.2D2 (http://www.pcengines.ch/alix2d2.htm) supports high powered USB cards and has a 1.0amp output ability on USB. The documentation doesn't say if this is 1 amp per port or 1 amp split between the two USB ports. I'm not sure if this matter since my math (P=IV) says that the ALFA cards require .2amps each. The ALIX documentation (http://www.pcengines.ch/pdf/alix2.pdf) says the ALIX board itself requires 6W at peak usage without USB or mini-pci cards. I am powering the ALIX board with 18W (15V, 1.3Amp) power supply.
Any idea if the Alix board will be overloaded?
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I'm not sure if this matter since my math (P=IV) says that the ALFA cards require .2amps each.
If the card generates 1W of radio output then it will need more than 1W of electrical power input (no electrical circuit is 100% efficient in doing these sorts of conversions).
I suspect that with that many distinct transmitters in close proximity you might need to take some steps to ensure you aren't overloading any of the receivers. Directional aerials and/or shields might be required.
"Standard" USB practice is to allow up to 500mA current draw from a USB port. Hence the 1A USB power fuse is probably to cover both ports. Some USB devices requiring more than 500mA use an additional USB connector to stay within the 500mA per port.
Your power supply is probably adequate but without knowing the power consumption (or rating) of the mini PCI cards its not possible to say.
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I'm not sure if this matter since my math (P=IV) says that the ALFA cards require .2amps each.
First, your math doesn't actually apply the way you think it applies; the high output rates on the AWUS036H's is something similar to EIRP, i.e. a translation of dBm, and thus the antenna gain is factored in; it's not pure power draw. Whether ALFA actually accounted for connector/cable losses is another question, however. Look it up by FCC ID on the FCC.gov site to get a more accurate idea of the actual initial power.