In order to get the technical side of Signal Tide up and running, one of the central problems that we need to solve is the problem of making the right kind of chain.
We need to…
- Find the right location
- Get the right kind of antenna
- Mount the antenna on the right kind of gimballing mechanism (or not)
- Connect the antennna to the right kind of amplifier (or not)
- Connect that amplifier or antenna to the right sort of radio
- Get the right sort of signal from the previous steps
- Processed the signal through the right software
- And output the result to the right audio equipment
…in order to take the signal from the LES-1, and reliably play that as live audio.
This process, of chaining together different pieces of hardware and software, is not straightforward. So, over the past couple of weeks, we’ve tried out various different chains, and parts-of-chains, in order to try to answer this question.
One of the first things to do was to get GNU Radio up and running. Previously, we’ve been using gqrx as our SDR receiver software. There are some parts of GNU Radio already integrated into gqrx. However, for our next steps, we need to get a bit deeper in the weeds of SDR software, and so that requires installing GNU Radio, and using it via GNURadioCompanion.
Once we had it up and running (itself something of a tricky job), we needed something of a tutorial in how to use it together with the hardware we had previously been using when we went out to the hilltops outside the city. Meharban, our SpaceX saviour, gave us a run-through.
Once we had these parts all set up and ready-to-go, we had another early morning where we went out to try to monitor a pass of the LES-1. We set everything up at the top of the low hill in the centre of Hancock Park, which forms part of the La Brea Tar Pits Museum buildings.
We were again relying on GoSatWatch to point us in the right direction (quite literally), and we realised that it’s now possible to get push notifications (on iOS) when a specific satellite is about to start a pass over a specific location. Pretty cool.
We followed our morning monitoring by getting on the bus and going out to Griffith Park, in the Hollywood hills, in order to figure out whether or not it would be suitable for monitoring subsequent LES-1 passes in the coming days.
After we got there and figured out our spot for monitoring upcoming passes, we stayed for the sunset, and then left, got back home, and set our alarms. The next pass that we could monitor would be the following morning, beginning just before 7am.
So, we got to be able to see the same view, except this time we saw sunrise instead of sunset.
We were actually able to monitor two passes within a couple of hours at the top of the hill, on the grounds of Griffith Observatory.
In the evening we met up with Meharban again. He gave us an update on the application he had worked on for us in GNU Radio, having changed the audio codec, so that, all going well, we can listen to what we track. We also confirmed that the omni-directional antenna that we had been using is probably not going to give us a strong enough signal — one more part of the chain to switch around. The research continues.