Sun Nov 25 16:08:01 EST 2012
Trying out rtl-sdr
* FM radio demod works. (Q: how to sync the sampling rates of dongle
& audio card?)
* I have a Rafael Micro R820T tuner:
These tuners cover 24 MHz to 1766 MHz (locking again with lots of
gaps from 1850-1860 and 1900-2100). They also don't have the DC
spike caused by the I/Q imbalance since they use a different,
non-zero, IF. On the other hand, they might have image aliasing due
to being superheterodine receivers.
* Did some scanning using FFT view and NBFM demod. Found a beakon at
453.433M and multiple NBFM dispatch. 453.19M Police radio? Found a
reference here. Real frequency seems to be at 453.21250. Error
is is 50ppm. One of these constant ones is probably a DMR, probably
the trunking data line. There's some on 866MHz too.
* Found headphones at 911.03MHz. NBFM doesn't work. WBFM?
Actual chan 1,2,3: 912, 912.5, 913 MHz
* How to calibrate? Maybe local broadcast FM radio is best. Tuning
on 90.5 / 99.9 MHz when talk radio is on seems best, this makes the
sidebands quite visible on a sharp FFT. I'm at 100ppm correction.
* A bunch of narrow-spaced carriers at 149.7Mhz
* Very strong blip at 433.750, 1/minute
* Strong signals at 866MHz, 930MHz