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====== Automated RPi Weather Satellite Station Build ======

===== Introduction =====

2nd October 2022 - It is my goal to build a fully-automated station for the reception of APT and LRPT weather satellite images. The station will work on its own and store images for later extraction, possibly with a high-gain WiFi link for network access. This page will serve as a landing page for everything related to this project, from useful links with good information to my own notes as I think things out. 

I know how to do all of the software and cabling and frequently do this out in the field with a laptop and temporary setup, but the power and antenna/mount for a permanent, hardy setup is a bit difficult for me yet as I’m not very DIY-minded. My other projects are very “hacked together” as you may have seen from my various  articles on the Wiki.
===== Power =====

  * Some sort of battery system (how many mAh?) with management board for charging? Cost varies depending on type and voltage chosen, but [[https://www.ebay.co.uk/itm/354254105023|here’s]] a cheap 10,000 mAh LiPo flat-style cell that’s **~£12.99** and the [[https://uk.pi-supply.com/products/pijuice-standard|5V 2.5 Amp PiJuice]] is **£52.99** but it comes with a battery I won’t need
  * What voltage? I will need to step it down to 5V if too high
  * Solar panels? No experience whatsoever on this **£?**
  * How to efficiently use the power/battery? That’s a charge/power board’s job
  * Estimate/measure power drain of entire system - do I want a system monitor?

Literally no experience with this, but it seems easy from [[https://howchoo.com/g/mmfkn2rhoth/raspberry-pi-solar-power|this guide]] - I need a PiJuice, a solar panel and a regular LiPo battery with the standard 2 or 3 leads. I do have an old USB power bank I could use sitting there doing nothing, but it only has USB inputs/outputs and no 2/3 pin lead. I could disassemble it maybe and get at the insides, but that’s scary.

Other people are doing this with 12 Volt LNAs, so need a higher voltage battery and solar panel setup, plus a voltage converter to get it down to 5V AND a solar panel controller that will do 12V. Having said that most of the higher rated panels use 12V, so I would need to go this route if I can’t find a 5V panel of a decent rating.

Hopefully I just mount the PiJuice HAT, connect the battery and panel setup, and hopefully it’ll produce enough juice. The USB output current limit on the RPi shouldn’t be an issue hopefully, as I’ve used them off battery with a few gadgets like RTL sticks in before off a full 2A supply.

If there are any issues with current I may need a powered USB hub, which adds complexity and potential RFI sources. I would also like to know if there’s an alternative to the rather expensive PiJuice for all of this.
===== Hardware =====

  * (5V) Raspberry Pi V3B+ or 4? **£30-£40**
  * RTL-SDR dongle - lots of choices here, but I already have a Nooelec NESDR V3 stick that is perfect for this (current v4 listed here: https://www.nooelec.com/store/sdr/sdr-receivers/smart.html) **£30-£40**
  * (5V) BPF+LNA - many choices (expensive Nooelec ones) here, but this works off 5V and is low current, I have one from AliExpress and it seems okay: https://www.aliexpress.com/item/1005001627969372.html **£15 ish**
  * Possibly a Bias-Tee board to inject voltage up the coax to the LNA **£10 ish for a cheapo one**
  * Short USB extension
  * USB Wireless dongle with external antenna socket, plus pigtail and antenna, if I want live comms (ideally, future goal)
  * Any buttons or lights on the outside? Safe shutdown? Recording? Storage full? (all future goals)

On the non-RF side it’ll be a RPi 3B or 4, depending on what’s available. A 3B will do it just fine if I can still get them and will run cooler, but Pis are *very* sold out. I’ll maybe need a WiFi dongle with an external antenna socket to try and reach the long range to my living room router (this is a stretch goal really).

For the RF side I’ll need a receiver, and I have a spare RTL-SDR stick I can use for it. I also have a low-noise amplifier/bandpass filter for 137-138 MHz that will work over bias-T or USB, so I have options depending on where I mount the enclosure box with respect to the feedpoint of the antenna. The LNA/BPF should be close to the antenna feedpoint, requiring a bias-T (or a 1-2M micro USB lead, i guess...), but I’d like to put the box closer to the ground so if I put the amp/filter in the enclosure I can use USB easily - but how much will that degrade performance?

I may want to add some buttons or indicator LEDs to the outside, to shut things down or indicate a problem. These will need to visible outside and be waterproofed.
===== Software =====

  * The barest Raspbian OS install possible, probably  [[https://www.raspberrypi.com/software/operating-systems/|Raspbian Lite]]
  * [[https://github.com/jekhokie/raspberry-noaa-v2|NOAA-Raspberry-v2]] script with any mods found
  * [[https://github.com/altillimity/AltiWx|AltiWX]] is also an option for capturing more than one satellite at once
  * Try and move things off-SD card and reduce logging for card life
  * Secondary storage? SSD?

The smaller the install the better, the more automated the better, and the less work for the SD card the better. I’ll aim to optimise this setup, starting with the base install of the OS and script and then make changes or modifications as required.

Another useful modification is to make the RPi use as little power as possible by disabling onboard peripherals.
===== Antenna and Mast =====

  * Threaded rod V Dipole/Reflector (not good for all-around reception) or QFH (harder to make but better reception?)
  * Receiver nuts of some kind? How do I mount the rods to the PVC pipe if going with the V dipole?
  * Length of RG58, with SMAs to reduce adapter loss and then into enclosure (I will probably buy a pre-made cable) **£5-£10** depending on laziness)
  * 2-3m tall PVC mast - Wickes do these in decent lengths, 20mm wide with pipe clips to fit **£5**
  * Cable and (maybe) LNA/BPF inside pole, so will need waterproofing - how?
  * Some SMA joiners probably **£1-£3**
===== Enclosure =====

  * Enclosure MUST be weatherproof and have enough space to mount literally everything inside **£20-£50 depending on required size**
  * Pipe clips to mount enclosure to antenna mast **£5**
  * Cable clips or zip ties/sticky bases to secure things on the inside **£2-£3?**
  * Some sort of board stood-off from the enclosure wall, wood or plastic? Or attach stuff to inside wall of box?
  * Grommets or glue/seal for cable entry? Or use mounted sockets?
  * Velcro also an option for holding things inside the box

A test of my DIY skills, for decent protection the enclosure should be rated highly on the IP scale, I’m thinking IP67/68. This gets pricey, so I need to make sure I make the build relatively small and compact to save money.

I think I can use Velcro or cable ties and pads to hold most of it together on the inside.
===== Inspiration and References =====

Some relevant links and ideas will go in here as a scratchpad, as well as places to blatantly steal from..

There is prior art for this idea, and there’s two good ones here:

  * [[https://www.rtl-sdr.com/a-solar-powered-raspberry-pi-rtl-sdr-noaa-weather-satellite-receiver/|This one]] uses a 12V battery setup and a 12V LNA, and is quite heavily engineered. I hope mine will be a bit less complex, but the layout is basically similar
  * [[https://usradioguy.com/science/off-grid-apt-lrpt-satellite-ground-station/|This one]] does wind power too and is way overly complex for me