Having trouble locating a Raspberry Pi for a weather balloon tracking station? Consider the Libre Computers Le Potato as a less expensive alternative. Currently $30-40 on Amazon, it is a very good choice for this application. Currently we have 3 Le Potatoes in operation.
The Le Potato can be ordered with 1 or 2 gb of on board memory. The power requirements are 1.5 amp, which is less than a Raspberry Pi 3. NOTE: USE A 3 AMP POWER ADAPTOR IF RUNNING 2 SDR’s. It uses the same accessories as the Pi 2-3 series. The chip placement is slightly different inside so using one of the Pi 3 series cases with the metal posts that press against the chips should be avoided as the smaller post will not rest on a chip. Heat from the Le Potato is much less and my case barely gets warm vs the Pi 3B that ran hot to the touch in the same case. I am only using the larger heatsink included with a generic RP3 case on 2 of the Le Potato CPU’s. (As of Sept, 2023, a heatsink is available for the board and I have one of those in use.) Libre Computers offers a Raspbian image download on their site. It is a little quirky with setup requiring me to use the command window and nano to enable SSH instead of setting it from the desktop.
Specs:
- Form Factor Compatible with Raspberry Pi® 2/3 Model B/B+
- Quad 64-bit Low Power Cores
- Penta Core 3D GPU with OpenGL ES 2.0
- Amlogic Video Engine (AVE10)
- H.265
- H.264
- VP9
- HDMI 2.0 with 4K HDR support
- Up to 2GB DDR3
Visit them at https://libre.computer/products/aml-s905x-cc/ for specifications and other information.
The downside of the Le Potato is the lack of WIFI and the internal display interface connector. It also only has a 10/100 ethernet port. The lack of wifi is resolved with using a dongle with a Realtek chipset. NOTE: Amazon Special Sept 2023 2 gb RAM with heatsink and wifi dongle $40.This has been a plug and play solution on the 2 potatoes I have ordered.
https://www.loverpi.com/collections/le-potato offers a WIFI dongle that is compatible and it is available on their website or from Amazon at a higher price https://amzn.to/3Xsgy5n. There is a 5 minute youtube video that explains how to install it to work at this link https://www.youtube.com/watch?v=30VZ_OowuN8
NOTE: This is a work in progress and I will edit, add, or delete information from time to time.
Below is a list of things from Amazon required to assemble a working weather sonde balloon tracking station. If something is out of stock or has a long delivery time, you may want to substitute a similar item.
https://amzn.to/3wlkUiQ A complete shopping list less the Wifi Dongle, but it is included in one package deal.
You will need a USB keyboard and mouse, HDMI cable to plug into a HDMI port on your TV OR a HDMI to VGA (like this https://amzn.to/3Hl2Hbd ) or DVI adaptor ( like this https://amzn.to/3wkzuqL ) for a computer monitor for programming. Also a USB micro SD card adapter to load the Raspbian image to the micro SD card. Once the Le Potato is setup, the monitor/TV and usb keyboard and mouse are disconnected and the device operates in stand alone mode with only the power, ethernet cable or dongle, and SDR-RTL connected. XRDP may be installed and then Windows Remote Desktop will work on the Potato or Pi.
You will also need a vertical UHF antenna. This can be anything from a small ground plane or fiberglass stick type to a 21 ft repeater antenna. Anything 400-470 mhz seems to work. Currently I am using a 21 foot 450-470 mhz antenna on one of stations. Coax and appropriate connectors/adapters to connect to the SDR-RTL. Avoid using RG58 and RG8X cables to feed outside antennas as the losses on even short runs are significant at UHF. The higher the antenna is in the air, the farther away it will receive. AA4BS was using one of these for his tracking station. https://amzn.to/3wm0sy2 until it was moved to another location.
Don’t forget to purchase a SMA adaptor cable of your choice of connector to connect to your coax such as this one https://amzn.to/3ZYrRUo.
Putty may be used to SSH into the Le Potato and nano used to edit the station.cfg file. The RTL-SDR gain of -1 is default for automatic control of the AGC. If using multipl RTL-SDR’s, you must assign a serial number to each one following the instructions on the Auto_RX setup page. Seralize your SDR’s starting at SN 10 to minimize port conflict issues using rtl_eeprom -s command.
XRDP can be installed after setup and you can use Windows Remote Desktop to access the Potato.
Auto_rx is loaded once you have the Raspbian running on the Potato. Follow the instructions at
https://github.com/projecthorus/radiosonde_auto_rx/wiki
Some pointers with accessing Auto_RX –
If you are using the local console (mouse, keyboard and monitor on the Pi or Potato), type in the web browser URL box 0.0.0.0:5000 to view whats going on with Auto_RX
If you are on the local network with another computer, either look up the device in your router or use a network ip scanner to identify the IP address in use. It should say Raspberry Pi in the device list. Type in the web browser URL box the IP address of the Pi or the Potato and add :5000 to the end of it, example – 192.168.1.98:5000.
To enable the controls available in the web browser, you edit the station.cfg and set a password for it.
Sometimes we have experienced some issues after days of continuous operation where the SDR stops working. Sometimes it has been exposure to local strong HF transmissions and other times it seems to be power related. I have added a reboot cron job to our Pi images so it reboots every morning at 5 am. Instructions to add the command is here https://smarthomepursuits.com/how-to-reboot-raspberry-pi-on-a-schedule/
AA4BS experienced an issue with both a PI3B+ and the Potato with them disappearing off the network and the only way to see them again was to reboot. This seems to be a known issue with the fix being to assign the PI/Potato a static IP address within the Raspbian config file instead of using DHCP.
Multiple SDR’s
The Le Potato will power 2 SDR’s. NOTE: USE A 3 AMP RATED SUPPLY FOR 2 SDR’s OR A POWERED USB HUB!! Do not plug more than 2 SDR’s directly into the Potato. One SDR must be plugged into USB port 1. This is the USB port closest to the ethernet port locking tab hole. This USB channel 1, The other 3 are on USB channel 2. The more SDR’s attached to the Potato or Pi, the more bogged down it becomes. 3 seems to be about the limit and requires an external powered USB bus. My recommendation is no more than 2 and use a 2 port splitter. You must change the serial number from the default 0000001 to something else when using more than 1 SDR. Due to port conflicts, do not assign 2, 3, or 4. I suggest starting at 10.
If you are using more than 1 SDR, a splitter should be installed and a preamp placed in front of the splitter. Also a 403 MHZ SAW filter should be used between the preamp and antenna. Any unterminated ports on the splitter should have a dummy load attached. The auto gain value of -1 in the station.cfg should be reset to a fixed gain value, requiring some experimentation otherwise the RX will be overloaded unless you are using a 4 or more port splitter. A gain of 33.8 is a good value to start with using a 2 port splitter, Nooelec LNA, and a 403 SAW filter.
NOOELEC NESDR SMArt GAIN VALUES are 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
Serial numbers must be assigned to the SDR’s. For multiple SDR’s, a SN cannot be 1. Assign numbers above 4 (00000005, 00000006, 7, 8 etc) and I suggest starting at SN 10.
FM OR AM radio station overload
If you are within a few miles of an AM or FM radio station, you may need to install a AM or FM notch filter if you have some nasty looking stuff spread out on your scan plots. You will have to experiment on placement of the notch filter. In the AA4BS-1 station, a 94 mhz FM transmitter located about 1,000 ft away required the notch filter to be placed between the 403 SAW filter and the preamp. Installing it in front of 403 SAW filter was not as effective as placing it between the 403 SAW filter and the preamp.
Please don’t contact me for assistance in setting up your Potato or installing auto_rx unless you are willing to compensate me for my time. I enjoy my retirement!