The numbers you reach for on the bench: resolution bandwidth versus FFT length, probability of intercept, window selection, signal bandwidths, and frequency bands.
Resolution Bandwidth vs FFT Length
For sample rate $f_s$ in MS/s and FFT length $N$:
$f_s$ \ $N$
1024
4096
16,384
65,536
262,144
1,048,576
100 MS/s
97.7 kHz
24.4 kHz
6.1 kHz
1.5 kHz
381 Hz
95 Hz
245 MS/s
239 kHz
60 kHz
15 kHz
3.7 kHz
935 Hz
234 Hz
500 MS/s
488 kHz
122 kHz
30.5 kHz
7.6 kHz
1.9 kHz
477 Hz
1 GS/s
977 kHz
244 kHz
61 kHz
15 kHz
3.8 kHz
953 Hz
2 GS/s
1.95 MHz
488 kHz
122 kHz
31 kHz
7.6 kHz
1.9 kHz
POI vs Burst Duration
For a swept analyzer with given sweep time and 1 GHz span at 10 kHz RBW:
Burst \ Sweep Time
100 us
1 ms
10 ms
100 ms
1 s
10 ns
0.0001
1e-5
1e-6
1e-7
1e-8
100 ns
0.001
1e-4
1e-5
1e-6
1e-7
1 us
0.01
0.001
1e-4
1e-5
1e-6
10 us
0.1
0.01
0.001
1e-4
1e-5
100 us
1.0
0.1
0.01
0.001
1e-4
For an RTSA with 10 ns POI: any burst longer than 10 ns has POI approximately equal to 1.