talkabout

#!/bin/bash -x

# Record Talkabout channels as sound WAV files.

BW=250000
CHANNEL_BW=12500
FREQS="462562500 462587500 462612500 462637500 462662500 462687500 462712500 462550000 462575000 462600000 462625000 462650000 462675000 462700000 462725000"
STEP=2500

# Determine center automatically
s=0
n=0
for f in $FREQS; do
	s=$(($s + $f))
	n=$(($n + 1))
done
CENTR=$(($s / $n))
CENTR=$(($CENTR / $STEP))
CENTR=$(($CENTR * $STEP))

rtl_sdr -f $CENTR -g 30 -s $BW - | ./nfm.py $CENTR $BW $STEP $CHANNEL_BW $FREQS . -a $*

# See CFR §95.1763 GMRS channels.
#  The GMRS is allotted 30 channels—16 main channels and 14 interstitial channels. GMRS stations may transmit on any of the channels as indicated below.
# (a) 462 MHz main channels. Only mobile, hand-held portable, repeater, base and fixed stations may transmit on these 8 channels. The channel center frequencies are: 462.5500, 462.5750, 462.6000, 462.6250, 462.6500, 462.6750, 462.7000, and 462.7250 MHz.
# (b) 462 MHz interstitial channels. Only mobile, hand-held portable and base stations may transmit on these 7 channels. The channel center frequencies are: 462.5625, 462.5875, 462.6125, 462.6375, 462.6625, 462.6875, and 462.7125 MHz.
# https://www.buytwowayradios.com/blog/2006/07/frs_and_gmrs_frequencies.html