johnny@johnnyhp:~$ rtl_power -f 123.5M:135M:2k -g 10 -i 3 -e 2h -c 50% spyhf2.csv
Range: 123.5M:135M:2k
Mode: normal
Number of frequency hops: 0
Dongle bandwidth: 4000Hz
Downsampling by: 1x
Cropping by: 0.00%
Total FFT bins: 0
Logged FFT bins: 0
FFT bin size: 2000Hz
Buffer size: 16384 bytes (2048.00ms)

rtl_power, a simple FFT logger for RTL2832 based DVB-T receivers

Use:	rtl_power -f freq_range [-options] [-f freq2 -opts2] [filename]
	-f lower:upper:bin_size [Hz]
	  valid range for bin_size is 1Hz - 2.8MHz
	[-i integration_interval (default: 10 seconds)]
	 buggy if a full sweep takes longer than the interval
	[-1 enables single-shot mode (default: off)]
	[-e exit_timer (default: off/0)]
	[-d device_index (default: 0)]
	[-g tuner_gain (default: automatic)]
	[-p ppm_error (default: 0)]
	filename (a '-' dumps samples to stdout)
	 omitting the filename also uses stdout

Experimental options:
	[-w window (default: rectangle)]
	 hamming, blackman, blackman-harris, hann-poisson, bartlett, youssef
	[-c crop_percent (default: 0% suggested: 20%)]
	 discards data at the edges, 100% discards everything
	 has no effect for bins larger than 1MHz
	 this value is a minimum crop size, more may be discarded
	[-F fir_size (default: disabled)]
	 enables low-leakage downsample filter,
	 fir_size can be 0 or 9.  0 has bad roll off,
	 try with '-c 50%'
	[-r max_sample_rate (default: 2.4M)]
	[-P enables peak hold (default: off/averaging)]
	[-L enable linear output (default: off/dB)]
	[-D direct_sampling_mode, 0 (default/off), 1 (I), 2 (Q), 3 (no-mod)]
	[-O enable offset tuning (default: off)]

CSV FFT output columns:
	date, time, Hz low, Hz high, Hz step, samples, dbm, dbm, ...

Examples:
	rtl_power -f 88M:108M:125k fm_stations.csv
	 creates 160 bins across the FM band,
	 individual stations should be visible
	rtl_power -f 100M:1G:1M -i 5m -1 survey.csv
	 a five minute low res scan of nearly everything
	rtl_power -f ... -i 15m -1 log.csv
	 integrate for 15 minutes and exit afterwards
	rtl_power -f ... -e 1h | gzip > log.csv.gz
	 collect data for one hour and compress it on the fly

Convert CSV to a waterfall graphic with: