Entry 002 / 2026-09-08 / Radio research

Picking a radio for a 250 gram satellite is harder than I thought

So, as I go down the path of planning my PocketQube build, I kinda have to pick a starting point, and the radio feels like the right place to start. I spent this last weekend doing quite a bit of research and, well, I realize I need to spend more time doing research ;)

The radio is super important, if anything goes wrong with it, I could build the perfect PocketQube and I would never know it because I wouldn't be able to communicate with the thing.

There are a lot of challenges when you need a satellite this small, looking at quarter-wave antenna at 435 MHz the length of the antenna itself is ~17cm, but my satellite is a 5 cm cube, so the antenna has to be deployed in orbit.

And this is where there's sooooo many things that can go wrong, but of course, many other people have thought about this, so it's less risky in some ways because I'm not the first person to come up with a solution here. There are plenty of references I can use to model this, but like most things in space, there will be a ton of variables I can't really control for, or know about, until the satellite is in space.

I'm also not in a place to build and test a bunch of these. If I had $100,000 just to put towards a hobby like this, then I could have some good test runs, but right now, this really is just a one shot dream for me.

Okay, but let's get to the good stuff, some of the decisions I'm making around the radio.

Band: relatively easy decision, 70cm amateur band, which would be in the 435 - 438 MHz range seems like the sweet spot. Sure, everything will be public, but that's okay, I'm just doing this for fun so if other people want my data, they can have it.

Modulation/protocol: there's a tradeoff here between sensitivity vs. data rate, like band, I just want to go with something straightforward so I'm going with GMSK/FSK. If you don't know what any of this means, there's plenty of info out there about GMSK/FSK vs. LoRa that you can read about but I won't go much deeper in this post.

The physical part itself: this is probably where I'm the most stuck right now, lots of choices, and I really want to make sure to get something that works well at super cold temps because space is cold.

For anyone wanting to know what I've narrowed it down to, here's what I'm comparing:

Okay, this post ended up being a lot longer than I expected so I'll stop here. I never write any posts on this site with AI, this is just me rambling on as I figure out how to build my first PocketQube. Onward!