Any physicists here?

Cromulent · 12 Aug 2022 at 19:49

I need to learn about radio, but I have no idea where to begin.

I need to learn it because I'm currently teaching myself electronics, and I need to figure out how to send wireless data while abiding by the radio spectrum licensing laws. I don't think I've ever studied radio before, so I feel lost. If someone could recommend a beginner-level book and one more advanced to move on to next, I would appreciate it.

Thank you!

Cromulent · 13 Aug 2022 at 00:22

NickK said:
I have repaired an old 1957 tube radio and have some basic AM/FM understanding. Transmitting over the air is a different kettle of fish - you will need to pass exams, licences and test gear (ie a RF spectrum analyser) to understand what you're transmitting. You may want to talk to a HAM radio enthusiast @Feek - there's also a thread on this.

You can 'send' it by simply carrying through a shielded coax cable. That way it doesn't need to go across the air and is weak enough not to be transmitted - "direct signal injection". This is a technique often used for tuning radios where a signal is generated (a modulated signal for AM or FM) and that is injected into the radio which is tuned and then bobs your uncle.

An fast oscilloscope FFT works to give a spectrum but it's not brilliant. I have a little Silent SDS1104X-E that runs at 200MHz which can see radio RF which can FFT at a push but it's not the best thing in the world (compared to a real SA).

Expect £1K+ for an RF spectrum analyser (2K+ for a Siglent starter) or cheaper for a second hand known brand. Just don't bother with the cheapo SAs. Expect ~1-2K for a FM capable AWG waveform generator to generate a signal.

Without a SA you will not know what harmonics or other noise you're possibly going to transmit and it's very likely that you'd need to provide that (and have it independently tested) to be a licensed transmitting device.. last thing you want is the police turning up and seizing everything and then fining you for accidentally transmitting on restricted/emergency bands.

Thank you very much. I'll have to look around and see what I can afford.

dLockers said:
You guys have all been sucked into a cromulent hole. Basically someone recommend him loads of expensive gear and never hear from this hobby ever again.

I'm curious, but do people follow me around on this forum? I mean, fair play if you are interested in everything I post asking questions; I just find it weird. But to explain, I've been unwell and often latch onto ideas to distract myself. This keeps me happy instead of doing nothing, which would depress me.

Cromulent · 13 Aug 2022 at 01:06

Minusorange said:
LoraWan is sufficient for most hobbyists where bluetooth and wifi isn't long range enough

I’ll look into that. Thanks.

Cromulent · 13 Aug 2022 at 01:41

Philtor said:
Umm WiFi? People have already figured this out btw.

Sure. But you won’t learn much if you just copy everyone else.

Cromulent · 13 Aug 2022 at 12:20

Philtor said:
Bluetooth? Are you wanting to create a new wireless standard? Have you been drinking?

No. Sorry I wasn't clear. See below for what I want.

firstborn said:
How about you say what you want to transmit, and over what distance and then you may attract some sensible answers.

OK. I'm sorry to everyone for not being clearer.

What I want to do is similar to WiFi Direct or Bluetooth Mesh. One (or more) device(s) will send data over a specific frequency for a reasonably short range. Still, instead of clients having to connect to the server or sender explicitly, they can passively receive data by constantly checking the specific frequency.

I have read of WiFi Direct and Bluetooth Mesh, but neither seems to offer that feature. If I am wrong on that, then feel to correct me. As I said, I'm just learning.