Update rtlsdr_usage notes.Typos fixes and some additional notes

1 files changed, 33 insertions, 20 deletions

diff --git a/md/writeup/rtlsdr_usage.md b/md/writeup/rtlsdr_usage.md
index a1440ce..b6e0eed 100644
--- a/md/writeup/rtlsdr_usage.md
+++ b/md/writeup/rtlsdr_usage.md
@@ -6,11 +6,12 @@ keywords:linux,rtlsdr,gqrx
 
 
 By rtlsdr usually call RTL2832U chip based tv-tunners which
-can be used for not just recievin DVB-T frequencies but much more
+can be used for not just receiving DVB-T frequencies but much more
 and yes price is ~$10 it mean that anyone can just buy and try
-without "loosing" money.
+without "loosing" money. None of examples below requires any modifications
+or extra hardware to run.
 
-As of 2022 the cheap that commonly available is r820t2.
+As of 2022 the version r820t2 that is commonly available.
 
 
 ### Get sources
@@ -85,16 +86,21 @@ then adsb data from plains is received.
 ## Collection of tools  
 
 
-### FM
+### rtl_fm, FM modulation
 
-Get some sound trancmited from FM radio stations.
+Get some sound transmitted from FM radio stations. 
+Find local radio station and set frequency choose wide band FM modulation __-M wbfm__
+set SDR sample rate to any supported, but more then 150kHz, for example __-s 200000__.
+Resample SDR output to audio frequency __-r 48000__. Pipe output to any audio tool
+here is example for aplay where sampling rate set to same resampled rate of SDR.
+IQ format from rtlsdr is signed 16 bit little-endian __-f S16_LE__. 
 
 ```bash
   rtl_fm -f 96.3e6 -M wbfm -s 200000 -r 48000 - | aplay -r 48k -f S16_LE
 ```
 
 
-### Spectrum diagram
+### rtl_power, Spectrum diagram
 
 Scan spectrum to find some activities on different frequencies.
 Good link with all description is http://kmkeen.com/rtl-power/ . 
@@ -107,13 +113,13 @@ and then draw image :
   heatmap.py fm_stations.csv fm_stations.png
 ```
 
-### ADSB
+### rtl_adsb, ADS-B
 
 ADS-B ( Automatic dependent surveillance broadcast ) in simple words airplane
-geoposition, speed, height and flight number broadcasting. You can receive
+geo location, speed, height and flight number broadcasting. You can receive
 this data and see how many plains is around and sometimes flight number.
 
-rtlsdr have default one rtl_adsb programm but it shows only received data,
+rtlsdr have default one rtl_adsb program but it shows only received data,
 without any decoding. Here is dump1090 specifically for rtlsdr and nothing
 more:
 
@@ -123,7 +129,7 @@ description howto install could be found also here
 
   http://www.satsignal.eu/raspberry-pi/dump1090.html
 
-Using in interactive mode with height in metrs:
+Using in interactive mode with height in meters:
 ```bash
   dump1090 --interactive --metric
 ```
@@ -137,15 +143,16 @@ Output:
 ```
 
 
-### AFSK1200
+### GQRX, FSK1200
 
-Gqrx is graphical SDR software where you can travel across frequencies
-and in real time search for some transmission.
+Gqrx is graphical SDR software where you can scan across frequencies
+and demodulate and listen FM broadcasts and HAM bands frequencies.
+Easy way how to explore the available frequency range
 
   http://gqrx.dk/
 
 It have built-in AFSK1200 demodulator or in simple words ham radio packets.
-And you could try to see what people sending in tex around the world.
+And you could try to see what people sending in text around the world.
 
 ### Multimon-ng
 
@@ -160,32 +167,38 @@ Here is few waterfalls for rtlsdr
 
   https://github.com/roger-/pyrtlsdr
 
-It have demo waterfall and aslo thats is python bindings to libsdr that
+It have demo waterfall and also thats is python bindings to libsdr that
 could used for fast prototyping
 
 ### rtl-entropy
 
   https://github.com/EliasOenal/multimon-ng
 
-Project that make rtlsdr as entropy source, uses FIPS 140-2 standart to
-verify that data is random enought to pass test.
+Project that make rtlsdr as entropy source, uses FIPS 140-2 standard to
+verify that data is random enough to pass test.
 
 ### rtl_433
 
-Generic data receiver. Can use to track remote sensors, weather stations and alot
-other devices.
+Generic ISM data receiver. Can use to track remote sensors, weather stations and many
+other devices. 
 
   https://github.com/merbanan/rtl_433
 
 
+```
+rtl_433 
+```
+
+
 ## Projects where rtlsdr used  
 
 ### WebSDR
 
 WebSDR probably best site where you can go and click on some radio receiver 
 and listen what happens in some particular country. WebSDR site contains
-about 80 radio recievers around the world that can be accessed trought web
+about 80 radio receivers around the world that can be accessed trough web
 interface. 
+
   http://websdr.org/
 
 If you want setup your own radio reliever read FAQ, prepare mail and send mail