Most important thing I have found is ALWAYS INSTALL AUTO_RX UNDER A LOGIN ACCOUNT USING pi AS THE USER NAME!!!! It will save you lots of debugging time. If you set up your OS with a different user name, add a user named pi and give it admin rights. Then log out and log into the pi account to install auto_rx from using that account, not under any other account.
Installing On Raspberry Pi
Pretty straight forward, just download the latest rasbian Bullseye 11 image from the official Pi website and install. Then follow the instructions from Auto_rx. It is very important to always install the auto_rx logged in as username pi. Been there, did it, had all kinds of issues. Also set up a chron job to reboot once every 24 hours otherwise you may find it locked up after a few days.
Le Potato
Install Pi image from their site, not from the official RP site. Same info from above paragraph. If wget and cmake are not installed, follow instructions below for installation.
PC
Installing on a PC – NOTE – Only done this on a couple of repurposed signage media players but it should be the same for any PC. These were Shuttle DS57U dual core 1.5 ghz with 2 gb of ram and 64 gb ssd drives.
Install Debian Bullseye 11. After getting everything updated and working on the fresh install, you must install CMAKE and WGET packages as 11 doesn’t seem to include them. It is very important to always install the auto_rx logged in as username pi. Set up a user account pi and give it admin rights. Log in as pi and then proceed to install auto_rx as a native install. Been there, did it under another username and had all kinds of issues that I never was able to resolve.
Use the commands below in the terminal window to install the missing packages.
$ sudo apt-get install cmake
$ sudo apt-get install wget
Then follow the instructions to do a native install of auto_rx.
MULTIPLE SDR’S
When using more than 1 SDR, each SDR must have a unique serial number. NEVER EVER assign serial numbers 1, 2, 3, and 4 to a multiple SDR station. auto_rx will randomly disable a SDR when it has a conflict with the device port. My suggestion is start with SN 10 and increment up.
Change your SN—- Only 1 SDR can be plugged in. If you have multple SDR’s, unplug them all except for the one you are changing. To view the SDR information, “sudo rtl_test” will return information on all SDR’s connected and run a test. To exit the test, “crtl-C”. The command to change the serial number on a SDR is “sudo rtl_eeprom -s X” where “X” is the new serial number. “sudo rtl_eeprom -s 10” will change the SDR serial number to “10”. Unplug the SDR and then plug back in to complete the update. rtl_test should show the new serial number assigned. Once you have changed the serial numbers on all your SDR’s, you can plug them all back in and run rtl_test to view that they are working.
GAIN VALUES
If you have a single SDR with no preamp leave it at -1. Adding a preamp without a 403 mhz bandpass filter (also called a saw filter) will have the SDR overloading and require experimentation with the gain value for best signal to noise. Depending on how near you are to any AM or FM broadcast transmitters, you may also have to add an AM or FM broadcast notch filter between the preamp and the antenna. Any splitters in the system are between the preamp and the SDR’s. A 403 bandpass filter and any notch filters are between the preamp and the antenna. Placement of the notch filter for best reduction of FM interference requires experimentation. In AA4BS-1, the notch filter is between the preamp and the 403 bandpass filter. In N4FV-2, its between the 403 bandpass filter and the antenna.
The best gain value for me sets the noise floor around 30 to 40 db where no signals are present in the plot. This is not a game of who can get the strongest signal but decoding the signal where the signal to noise ratio is more important than how strong it is.
N4FV-2 is a 4 SDR station. I use a communications grade 4 port 50 ohm splitter with 6 db loss per port, 20 db gain preamp, 3 db loss 403 bandpass SAW filter, an FM notch filter, all in that order. The overall system gain is around 10 db and did not require any adjustment in the gain level (-1 auto level) in the station.cfg. If you assemble a similar station, it might require a gain value setting. If you are using a 4 port splitter and have less than 4 SDR’s, each unused port should be terminated in 50 ohms.
AA4BS-1 is a 2 SDR station using an “improvised” 2 port splitter, preamp, FM notch, and 403 bandpass filter all in that order. A BNC “T” is used as the splitter with 2 BNC to SMA cables to divide the signal. Adapters then attach the splitter to the preamp and filters. The gain value is currently set at 42.1 in the auto RX station.cfg for this station.