Alex and I are seemingly both interested in the same experimental zone at the moment, and here he has built an interesting 'Long Range Wireless' setup for UHF which he found on the Instructables website at https://www.instructables.com. This is a 'maker' community that was purchased by Autodesk around eleven years ago, and fortunately they haven't tried to turn it into a money-maker or promotional tool. It contains an extremely wide variety of very do-able projects and is worth looking up.
There are several radio-related practicals hosted there including this one. It's an Arduino-based data communication link which utilises an HC-12 wireless UART serial port module at each end, which in theory - given the right conditions - can achieve a range of up to 1km.
Alex had kindly provided a photo of his setup, and a copy of the HC-12 User Guide.
There is no need to repeat the content of that guide here, and although the translation into English isn't perfect, it is pretty clear what's going on if you wish to try it yourself.
I'm currently building something very similar to support the SDR Training Academy course, so I'll also be cloning this project to see how the two compare.
This is an ISM band experiment capable of operating in a frequency range of 433.4MHz to 473.0MHz at max 20dBm, BUT it is obviously your responsibility to ensure you stay within the UK ISM band limits. At the time of writing, these limits for the 433MHz allocation are 433.05 to 434.79MHz. Assuming you stay within that slot, there is no operating licence required due to the low power radiated. I've included the relevant Ofcom document FYI as of March 2023.
Thanks again to Alex M0TOT
HC-12 Wireless Communication Module v2.4 | Ofcom UK ISM bands Frequency Allocation Table |