I just wanted to report this in case it could be possibly related to firmware and not exclusively the hardware.
On the AR150 if I connect any Ralink adapater (I have tried a few) the syslog will report the USB device disconnecting and reconnecting repeatedly. I believe this is because the AR150 is disconnecting USB power when it over drawn. However, I think I saw in another post that the cut off is a high as 1.5 amps for that to happen.
I hooked it up to bench power supply so I could see exactly what the power draws are and ensure it was not due to the 1A DC power supply (my bench supply can go up to 400w, so definetly not a problem). Before the adapter connects it is drawing about 0.150 amp. When the adapter connects it goes up to ~0.280 amps, and then it disconnects and goes back to .150, and just constantly repeats.
I have seen the behavior on the WR703N but if I set the txpower so something like 23 instead of 30 it would be fine. I was thinking the same would apply here, but I have put the txpower to as low as 10dbm and it doesn’t matter. If I power the adapter separately or by a powered USB hub it works fine. It can only mean that either the hardware cutoff amp is very low, or if it is being controlled by firmware that that code that is controlling the power cutoff is too low or has a miscalculation. I had a feeling it could quite possibly be controlled by firmware with current sensing since it is already tied to a GPIO to turn it off and on.
I noticed that you can power the router from the USB port instead of the mini usb power port, so I think for a short term fix I will be inserting 5V directly to the USB port pads/pins, but it would be tedious if we end up using these because I will have to do it to dozens, if not hundreds of them. That is why I am hoping there is a solution to get the required power from the USB without modifying the hardware.
PS- If the power limitations are hardware based in the AR150, would the 6416 perhaps be better equipped at USB power since is not tied a GPIO?