USRP-1 with resistor ladder front-end board and custom FPGA build as used by the radR USRP plugin
Furuno FR-1964 radar, set to short-pulse mode but left on standby.
Wavetek 907A-S-792 signal generator; tuned to 9.49 GHz (fine-tuned to maximize USRP output values); pulsed output; 6.25 microsecond pulses @ 500 Hz
12' of LMR400 Ultraflex coax cable
N-connector to waveguide adapter. UG-446A/U Mfg Code: 01882 VSWR: 1.25
a short R script ran the test_usrp_bbprx program (a diagnostic tool distributed with the radR USRP plugin) to capture digitized samples
the trigger sync signal from the Wavetek was connected to the USRP's trigger input
the video signal from the Furuno was connected to the USRP's video input
the USRP sampled at 64 MSPS for 1024 samples per pulse.
USRP video-channel gain was set to 0 dB
201 samples from the middle, stable region of each pulse were captured
20 pulses approximately 1 second apart were sampled at each power level
at each power level, mean and SE of the USRP digitized value was calculated. (Mean was mean across 20 * 201 samples; SE was mean SD across 20 pulses, divided by sqrt(20)

Results:

The loss for the cable and N-waveguide adapter is estimated to be 1.53 dB (1.48 dB for the cable, as calculated by some online RF cable attenuation calculators, and 0.054 dB loss in the adapter).

Here is the plot of signal value imputed for a range of sample values returned by the USRP:

This is the power arriving in the flexible wave guide attached to the feed horn behind the dish antenna.
To get the incoming power from the target, you need to also calculate the antenna gain factor. For the 55 cm
dish, this is around 30 dB.

Calibration

From $1

Table of contents

Table of contents