On 25/03/2023 15:45, George Edwards wrote:
Hello GNURadio Community,
I am about to use a N310 radio to transmit and receive data. My
problem is I do not know how to interpret the sample rate parameter. I
will pose some questions that I am seeking answer to (I read there are
3 Master Clocks for the N310):
Q1. The transmitter Sample Rate setting: is this the sample rate of
the data that will enter the N310 hardware from the GRC software
component?
yes.
Q2. The receiver Sample Rate setting: is this the sample rate that the
N310 hardware outputs the connected GRC software component?
Yes
Q3. Now I was reading the interpolation/decimation in the N310 radio
and there were statements made about the device having 3 Master
Clocks. Let's assume I choose the Master Clock frequency of 125e6 for
the transmitter and I wish to upsample by a factor of 100 in the N310
transmitter. I take it that this assumes that GRC component connected
to the N310 USRP Tx block must be running at a sample rate 1.25e6 and
that by setting the Sample Rate in the USRP block to 1.25e6 (with the
Master Clock set to 125e6) then N310 hardware will upsample the data
entering to 125e6, right?
Yes.
Q4. Now, for the converse at the receiver: with the USRP Master Clock
set to 125e6 and USRP Sample Rate set to 1.25e6, then the USRP block
will deliver a sample rate of 1.25e6 to the attached GRC component,
right?
Yes,
Q5. What happens if I do not select one of the Master Clocks, but
provide the Sample Rates at the respective USRP Tx/Rx?
The default master-clock if you don't specify in a device argument is by
default (as I recall) 125MHz. But that can be
easily verified by asking for some sample-rate that is a proper
fraction of 125MHz, and seeing if UHD changes it to
something different.