Re: [Discuss-gnuradio] USRP Power Supply Noise

[Matt Ettus]

On 08/24/2010 07:32 AM, Jeffrey Lambert wrote:
> Hello,
> I am attempting to build an analog front-end to a USRP 1 device. I have
> selected a VCO that will suit the frequency range we are looking at: It
> is an RFVC1800 and has a tuning range of approximately 7.4 - 12.4 GHz
> over a 13 volt tuning voltage. As this VCO is very sensitive to external
> noise, some power filtering will be necessary to minimize jitter and
> phase noise. What I would like to know is whether or not there are any
> other adverse effects from using the simple switch mode supply that is
> included with the USRP?
>
>
> Thanks,
> ~Jeffrey Lambert


The 6V supply on the daughterboards is filtered, but it is still 
unregulated, so it will rise and fall between 5.8 and 6.4V with load 
changes.  You'll want to pass it through an LDO to use it.

You mention 13V, which will take a switcher to boost the 6V.  In that 
case, you can use the 6V directly into your switcher, which should then 
be followed by an LDO to your final voltage.

Matt