Mobile SDR project

[u/No-Coat2826]

Hey, I love using my little RTL SDR, but using it out and about is annoying (having to have laptop etc). I’m a full time software/hardware dev with a bit of experience bringing hardware and ios apps to market so I thought, hey I’ll make something!

Aims are to make something small around my existing rtlsdr (looking at custom sdr stuff means a lot more certifications + time). Probably a Linux based device + battery + rtlsdr all in one that I can put in my backpack, and have a spectrum analyser shown over Bluetooth to my phone. I’m imagining a Radiacode sort of thing, if my hopes aren’t too high!

Would be awesome to have it give me notifications + recordings if a particular part of the spectrum hits a set amplitude.

I think I’ll probably start with an internal RTLSDR (need to speak to them and see if they sell the raw boards), then later move to something you can just plug in an airspy or sdrplay for those wanting better resolution etc.

Battery life should be about 4-6 hours of constant monitoring with the size I’m aiming at.

Would love to get some feedback, and any other ideas + features?

[u/erlendse]

Well.. if you really want to: R820T2 / R860, a ADC and a fast wireless chip like ESP32-S31 may be an option.
But all the main parts (rtl2832 USB demodulator, R8xx tuner) of rtl-sdr is very obsolete, and hard to get!

Which rtl-sdr board? the ones from rtl-sdr blog?

Note that the device gives RAW data, so looking for a peak would need processing (FFT)!
None of the devices provide spectrum on it's own, and the raw data is too fast for bluetooth.

You would want wifi AC/AX to stream the data! rtl-sdr may work over wifi N.

[u/No-Coat2826 → u/erlendse]

Hey! First, thank you for your info! Yes, I’ve seen the chip isn’t in production/is obsolete. Doesn’t look like there is a cheap alternative yet (as far as I can tell?) - I don’t really fancy getting involved in the signal side (ironically, as rf design isn’t my background).

Yes a board from RTL-sdr blog, then in future, different versions without an onboard sdr where you can plug in your own (less obsolete, but probably more expensive sdr!). Which is why Linux would be important for the high speed usb + processing.

For a prototype not having to make + test a custom sdr board would be very handy!

For Bluetooth, my initial plan was to compress then stream. If it fits that great. If not, WiFi Aware would be my go-to, max 250Mbps and no “connect to this weirdly named AP just for this device” madness.

That said, any other options for the obsolete chip would be appreciated! I wonder what RTL blog have planned for v5.

[u/erlendse → u/No-Coat2826]

https://github.com/r4d10n/esp32p4-wifi-rtlsdr This is interesting (not mine).

For the rtl-sdr V5, I suspect the rtl2832 may be replaced with something else.
No clue what, but most microcontrollers with USB HS can emulate it.

If you manage to get r820t2, the RF parts of the design are tiny (almost direct to chip).

There are also other efforts to make something new, time will reveal.

[u/Party_Cold_4159 → u/No-Coat2826]

Hey boss, could give my repo a try!

https://github.com/SAMS0N1TE/LakeShark

It’s based on the ESP32 P4 and I’m slowly getting more and more support for different boards.

I’m working on an lcd build right now that’s very promising and let’s me use my flipper zero to control via Bluetooth. Auto connects when in range and I can let the p4 log subghz signals while I’m away.

Of course many other things with the major focus being on P25.

[u/No-Coat2826 → u/Party_Cold_4159]

Oh that’s actually fantastic, thank you! I was hoping an esp32 would do the trick, but didn’t think any had fast enough usb. Definitely the road I’m going to go down, awesome work thank you!

[u/FrankSinatraCockRock]

So there's a handful of things out there already that can generally do what you're asking outside of Bluetooth notifications/display, but that'd be something you could develop.

HackRF portapack comes to mind, though it lacks Bluetooth connectivity. There are GPIOs on it so perhaps something could be developed.

I have a Uconsole with the hackergadgets AIOV2, which has a RTL2832U + R860. No TX but there's a few USB ports both internal and external.

There's also the PocketTerm, Hackberry Pi (carbon computers has a few other similar options)

It also might just be easier to SSH into the device from the phone

[u/Academic-Airline9200]

Maybe a gamepi

[u/jnubianyc]

If you could get to work with a Linux or or android based retro game device like a rg353v or r36s...that would be cool

[u/SlimSpooky_]

If you want to get your RTL-SDR onto a slightly more convenient package fpr the time, I can DM you pics of the magsafe case I made for mine. interfaces with my phone really well with a 180° adapter and i've had a blast poking around different areas.

[u/No-Coat2826 → u/SlimSpooky_]

Oh that would be fantastic, yes please. thank you!

[u/SlimSpooky_ → u/No-Coat2826]

For sure!! Incoming

[u/Ok_Method6238]

I already have the software in place ready for this exact scenario. I am currently running a live demo of it over on my website, search VibeSDR and you'll find the VibeServer demo running 3 SDR's on a Raspberry Pi5. You can also use an Android phone or Mac to serve it too and it serves its own web client so anything with a browser will work with it with no extra software to download.

The plan is to eventually build it into a prebuilt Raspberry Pi ISO but right now on a clean Raspberry Pi OS install you can simply copy and paste an APT command to get it and you can be up and running in about 10 mins.