How to resolve the uhd warning of sample rate

GNU Radio
1

Dear All,

I am using USRP1 having RF daughterboards WBX (50Mhz -2.2Ghz). I have
gone through some basic details of the USRP1 product features but dont
know how to resolve the errors oh UHD warning saying the hardware
doesnot support the target tx sample rate and same for the rx also.

Below is the USRP1 supported features :

ADC sample rate: 64MS/s
DAC sample rate:128MS/s
Host sample rate: 8 for usb2
FPGA clock rate: 64Mhz

Please help me to understand that what value of -r i should pass for the
both tx and for rx.

I
have tried with -r 250e3 and 125e3 but it could not work and popping
the warning that target tx and rx rate is not supported by hardware.

Thank you.

2

Hi Alok,

usually, it should say something like “actual sampling rate: XXX”. What
does it say? (actually, can you just copy&paste the whole warning?)

What program are you passing “-r” to?

Greetings,
Marcus

3

Hello Alok,

the problem here is that you implicitly request a lower sampling rate
than your USRP is able to provide:
“-r 250e3” specifies the bit rate. For “-m qam” (with a default number
of constellation points (-p) of 16=2^4) this means that the symbol rate
is 1/4 of that,
(250e3 b/s) / (4 b/sym) = 62500 sym/s. Now, the default setting for
samples per symbols (-S) is 2, so that you get 125e3 S/s, which is half
of what you can minimally do with your USRP.
You can either use a constellation with less points, increase your bit
rate, or increase your samples per symbol.

Greetings,
Marcus

PS: can you please generally reply to the mailing list and not to people
individually? It’s a bit hard for me to keep track of this, and it might
be really frustrating for the others that follow these lists :wink:

4

Dear Marcus,

Thank you so much for your help :). It worked fine.

Regards!
Alok