Hi GNU Radio users,
I am experiencing some interesting noise
captured on a signal analyzer when trying to playback a
captured signal using an Ettus B200 with both GNU Radio blocks
and UHD example code. The UHD example code I am using is:
- “rx_samples_to_file
--rate 5000000 --freq 500000000” for capture
- “tx_samples_from_file
--rate 5000000 --freq 500000000 --file
/home/path/usrp_samples.dat --gain 30” for playback
The GNU Radio blocks I am using are simply
a USRP Source into File Sink for capture and a File Source
into USRP Sink for playback (both programs operating at a 10M
sample rate).
The signal I am capturing is a 500MHz pure
sine wave fed directly out of a signal generator into the
TX/RX port of the B200. The playback with noise I am receiving
is directly out of the B200 TX/RX port into a signal analyzer
and is pictured here:
Is this peak 1kHz from the carrier
expected? Could this be the LO or some other noise on the
board leaking through due to a lack of filtering? Is this
re-creatable on other hardware? I can send the captured data
if there isn’t an obvious answer to why there is a signal at
499.999MHz.
Another piece to the puzzle I feel like I
should mention is that when running “tx_waveforms –rate
10000000 –freq 500000000” and feed it directly into signal
analyzer the output is only a peak at 499.999MHz…
Is this offset within tolerance of B200
hardware, or is there a bigger issue happening here?
Thanks in advance for any help,
Nick Restivo