I am wondering if the RFD900 hooked up via usb / OTG cable does anybody have concerns that in full power setting it will be under powered from the droid? I'm by no means an electronic wiz so could be I'm worrying about nothing but as I recall on max setting it's 1000 Mah? There must be a limit on the power over the usb? is it 1000 Mah or more on most devices?

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I think you'd have to check each device.  I don't think most android devices have smart current limiting - if you go over the USB spec the device will probably just brown out.  So RFD900 might work on some devices but not others (or you can peel off the power and provided 5V some other way).

900mA is the max per spec.

and if you start to brown out you can always lower down transmit power on your RFD900 modems.

good idea!

Thanks for the replies. Well I guess the proof is in the pudding so to speak it appears to work just fine. Wether or not the radio's range is affected by a potential marginal [?] power supply I don't know yet so I guess I will just need to go flying and confirm that it works without a shorter range issue. 

Keep us posted on range test results.

I have been using RFD900 on my Samsung 8" Note and Note 2 phones without any problems. Powerlevels were defaults eg. 20 so not full power but let's say around 65% so enough.

Good to know thanks! off topic a bit but what kind of range did you get at %65? I have not had a chance to try mine yet between bad weather and work. I'm hoping to get 5 miles with one on both ends. With a spotter of course. 

5 miles should be easy to get... i don't know, never got out of range so far :)

There are reports that some one got up to 65km with those on full power. Seppo (owner of RFD) has tested modems and he's getting 20+km easily

I use the RFD900 with a Nexus 7. I definitely am getting reduced range.. probably about 2km before very low rssi, which seems terribly short.

Is it OK to power the RFD900 separately? that may be the only way for me to get full range using the tablet..

yes, as long as the data and ground signals are hooked to the tablet, powering the USB device with a clean 5V supply should be fine.

thanks! Splitting the ground into two is OK (one for USB, other for battery)?

you want to connect the grounds together, and make sure to use a regulated 5V supply for the radio (not just a battery)


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