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 Post subject: Power draw
PostPosted: Sun Aug 20, 2017 10:52 am 
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Joined: Sat Jul 29, 2017 10:17 am
Posts: 4
Checking the specs I see that the max draw for the RS-UV3 and UVPA are rated for 9-16VDC. I am going to be attaching them to a 3D Robotics Solo drone that can supply 12-16.8 VDC up to 1.1 A (fused), which is beyond the power budget required according to the specification. But given the wide voltage tolerance what's a practical Wattage to expect to see?

For now I'm going to continue the build without the PA, but would really like to have it if possible. A separate payload battery is also an option, but max payload weight is only 700 grams and even a small load greatly reduces flight time (this is for a proof of concept and playing around more than anything).


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 Post subject: Re: Power draw
PostPosted: Sun Aug 20, 2017 9:14 pm 
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Joined: Mon Jul 23, 2012 6:25 am
Posts: 1142
Hi,

OK lets talk about the RS-UV3 first. In RX with the audio squelched the radio draws just under 150 mA. Since it uses linear regulators, the current draw is independent of the input voltage so the lower the voltage, the less the power. If the squelch is open and the output is driving an 8 ohm speaker you could see an additional 50-100 mA depending on the volume level.

On TX the total current draw was 240 mA on 2M, 250 mA on 1.2M and 270 mA on 70cm. Again this will be independent if the supply voltage.

The RS-UVPA draws 20mA for the LNA in RX which will be constant regardless of the supply voltage. TX uses a boost DC-DC converter up to 15.5V so it will draw less current at higher voltages and more at lower voltages. It also has a different PA for each band it takes 15-18W on 2M and 1.2M and 10-12W on 70cm.

You'll probably want to put a diode or 2 in serial with your 12-16.8V supply as 16.8V is a bit on the high side. 1.1A will be OK the RS-UV3 alone and possible the RS-UVPA on 70cm. You'll need to add some power to run on 2m or 1.2m.

We are in the process of updating the RS-UV3 to the RS-UV3A which will have a boost-buck so the operating voltage will be 3-17V and more closely constant power rather than constant current. It should be able to run off anything from a pair of AA's to a UAV battery pack directly. Available this fall.

73,
Jim WA2EUJ


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