StepByStep.txt

Step by step instructions to use sdrrecorder (by MichelinoK) onto the Raspberry PI

Video (including qgrx loading the file) can be found here: http://youtu.be/4cbg87hLXCg

- Connect by ssh to the raspberry using the root user

- create a folder of your choice (let's assume /root/rec). This is where we'll download the script

- create folder where you want to record the i/q stream to be used by gqrx (let's assume /media).
In my setup, /media is a network share of my nas. You'll need a LOT of free and fast space to record the i/q stream!!!.
The Raspberry CAN handle that speed over ethernet (using 1.200.0000 samples/sec).


- cd into the first folder you created (/rec)

- wget https://github.com/michelinok/sdrrecoder/blob/master/sdrrecorder.sh

- chmod a+x sdrrecorder.sh

- now edit the script with your favourite editor, I use "nano" and set your parameters.

Let's take a look at the first part of the script (where you've to set the parameters):


##############################################################################################################
freq=145800000		# ...so gqrx center must be on 146100000   ( i use  145800000 for iss)
fwshift=300000          # this is freqtuned-yourfreq (will tune to freq+fwshift) (i use 300000Hz as shift)
samprate=1200000        # recording samplerate
donglenum=1             # dongle number to be used
gain=0                  # gain to be used , i use auto
ppm=15                  # ppm correction
dest=/media             # destination folder
##############################################################################################################


"freq":the interested frequency to be recorded, in my case i wanna record the International Space Station (ISS)
"fwshift":the center of the spectrum will be shifted by "fwshift", so you'll be far from DC by "fwshift"
"samprate":this is (of course) the samplerate to be used, I use 1.2M to have enough spectrum to see other freqs
"donglenum":if you have more than one dongle, set it to the correct one, to secord the ISS I use my second dongle
"gain":the gain to be used...if you set it to "0", it will be "auto"
"ppm":the dongle ppm, nothing to say
"dest":is the folder you've created...where you wanna record the i/q stream



NOW an important thing...
Look at this line of code:

echo 'rtl_sdr -f '$tuneto ' -d '$donglenum ' -s '$samprate ' -p '$ppm ' -g '$gain ' -n '$samplestorec ' -X '$dest'/'$4 >> $dest'/'$4.sh

If you do not use my modded rtl_sdr or you don't wanna use RTL AGC, you've to remove the "-X", so the script will become

echo 'rtl_sdr -f '$tuneto ' -d '$donglenum ' -s '$samprate ' -p '$ppm ' -g '$gain ' -n '$samplestorec '  '$dest'/'$4 >> $dest'/'$4.sh

When i'll get a free time, this will be a parameter/switch, so you will not have to edit it anymore.





Now...how can i use the script? Edit the script and let's go on....

Let's take for example a pass of the ISS on 03/31/2015 at 06:06 of 5 minutes and we want a file named "iss_03312015.out"

You have to invoke the script with these parameters:

./sdrrecorder 06:06 03/31/2015 5 iss_03312015

the first paratere is the time
the 2nd is the date (remember....mm/dd/yyyy)
the 3rd is how many minutes you want to be record
the 4th is the filename you want (it will be created in "dest", in my case it will be created a file called iss_03312015.out in /media/)

Now you can logout from the Raspberry :)


What will happen?
A new script called iss_03312015.sh will be created in "dest" (containing all the steps to record/reencode) and it will be scheduled using the command "at" of Linux.
Once the recording has been done, the temp script will be deleted, the i/q file will be converted to a format suitable for gqrx and the original i/q file will be deleted.

That's all!

Remember to not record too many minutes... the space required to store the stream is HUGE!!!!


AS SOON AS POSSIBLE, I'LL EXPLAIN HOW TO LOAD THE FILE INTO GQRX AND "PLAY" IT.