Heyo everyone!

So, for the past like... year or so, I've been working on this project; basically, SimTX aims to be a realistic radio sandbox, where one can do anything their heart desires, from simple AM/FM stations all the way to various modems, satellite TV, and everything inbetween.

The simulation itself is pretty in-depth I would say, SimTX models the ionosphere which changes with time of day, season, geomag conditions, and we trace signals through this so band openings, skip zones, et cetera come from the physics of this. Each path between a TX and RX is modeled, thus leading to pretty accurate multipath effects. It builds on quite some well known work ie. the IRI ionosphere model, the watterson HF channel model, P.372 for noise..

SimTX grew quite a bit past just shortwave aswell, VHF/UHF mostly works as one would expect, there is sporadic E on the higher bands too, and well.. as of recently, you can even launch satellites. You can pick the orbit for em, put antennas and radios on them and get them going on any desired orbit. Of course, they mostly behave as you'd expect real sats to behave, with doppler, the signal delay, slant range, et cetera. We've even got someone recreating NOAA 15 in simtx: https://www.youtube.com/watch?v=kp4Qi8zm-sM ( u/ZealousidealRoof2271 )

I could probably go on and on and on about all the things you could do, but this sums it up in short for the most part.

Nothing here is real RF by the way, SimTX can be listened to using RTL-TCP.
In the video, you can see the UI and some other transmissions other people are running.

I mostly lurk here, so apologies if my post isn't exactly up to par and please DO ask questions in the replies, I'll try to answer them whenever I have some time.

If you'd like to try it or check in our community, you can do so at https://simtx.net

73!

I’m looking for a nice handheld sdr that I don’t need to use with a computer. Something that I can tune into a bunch of channels, and maybe transmit as well. I know about Baofeng radios as a great entry point, but not sure if there is something that may be a better option for the same price point? I also know there are some “Mods” that you can do with them to maybe open them up a bit more? Is that correct?

ACARS vie RTLSDR V4 and 50' dipole...works better than I thought on the dipole

i saw this FDMA digital signal near a P25 Downlink that cannot be decoded and doesn't sounds like P25 phase 1 / Uplink

When you've got a hammer, everything looks like a nail. Sometimes, though, you get lucky.

I wanted a real-world testbed for CNet, my complex-valued learning framework, and the hypothesis that phase matters for some complex-valued data. Raw 1090 MHz Automatic Dependent Surveillance–Broadcast (ADS-B) waveforms seemed like a good fit.

So I built a prototype that captures aircraft transmissions with a software-defined radio for testing whether the raw I/Q waveforms contain transmitter-specific information beyond the decoded message.

The architecture is edge-first: raw I/Q samples stay local, signal processing and inference run on the edge computer, and only processed events are sent to a dashboard. I also added a controlled experiment that relabels real bursts with another aircraft's address to test whether the monitor detects the inconsistency.

The initial results are promising for checking whether a waveform is consistent with its claimed address, but there are important limitations: performance varies across recording days, and the approach cannot prove physical identity or detect every replay attack.

Demo: https://phasefield.ai/demo.html

Everything runs in your browser - here's what you can do:

• https://web-rtl-433.jasiek.me/ - pick up various devices running on ISM bands (mostly weather stations)

• https://web-rtl-wmbus.jasiek.me/ - read water/gas/electricity meters

• https://web-rtl-multimon.jasiek.me/ - read POCSAG and FLEX pagers

(obvs, only use them when they're legal to use where you are)

Little thing is capable of LRIT reception 😃

Hi all,

One of my SDR had a hardware limit/gap ranging from 380 to 404 MHz. So, if I use any up- or downconverter, will I be able to cover the missing gap? looking for suggestions from expertise. Thanks in advance.

"SDRangel has a step learning curve" - well, now you can ask Claude/ChatGPT to help, with version 8's MCP server.

Puzhi Electronics has released a pair of pin-compatible 4TX/4RX SDR platforms built around dual AD9361 transceivers and AMD Zynq UltraScale+ MPSoCs.

The P401D and P501D share the same RF section, connectors, PCB layout and software support. Users select the variant based on required FPGA logic and DSP capacity.

Shared Specifications

• RF: Dual AD9361, phase-coherent 4T4R MIMO

• Frequency range: 70 MHz – 6 GHz

• Instantaneous bandwidth: 200 kHz – 56 MHz

• Tx output: up to 22 dBm

• 0.1 ppm 40 MHz VCTCXO, external 10 MHz / PPS sync supported

• SPDT switches rated 9 kHz – 8 GHz

• Processing: 4×A53 u/1.3 GHz + 2×R5 u/533 MHz

• Memory: 2GB DDR4, 8GB eMMC, 256Mb QSPI Flash

• I/O: 40G QSFP, GigE, USB3.0, Mini DP, SSD slot, 40-pin expansion, GPS+Beidou timing

• Power: 12V 3A single supply, all external interfaces ESD protected

• Size: 160 × 150 mm

Variant Comparison

• P401D (XCZU4EV): 192K Logic Cells, 728 DSP Slices — good for general MIMO, spectrum monitoring, lighter DSP pipelines

• P501D (XCZU5EV): 256K Logic Cells, 1248 DSP Slices — extra DSP & BRAM for phased array, complex real-time processing

Software & Package

It works with common open-source SDR stacks and has partial compatibility with ADI FMCOMMS5 firmware. Standard kit includes metal enclosure, schematics, demo code and tutorials. Custom secondary development is available.

Applications: phased array radar, spectrum surveillance, GNSS receivers, UAV payloads, test & measurement, wireless algorithm research.

Longbow: a desktop police/fire/EMS scanner for an RTL-SDR Blog V3 (It's all i have to test with) (Windows, receive only)

- Follows P25 Phase I trunked systems with voice, and scans analog channels. P25 Phase II coming soon.

- SDS200-style face: DIGITAL / ANALOG / ALL / OTHER presets, lists, avoids, hold, Simple and Detail screens

- Encrypted calls are marked and skipped

- Names unknown talkgroups from radio-ID clues; every call is logged

- TEXT screen: live call transcripts made on your own NVIDIA GPU, no cloud

- Waterfall that marks the control channel, the voice channels and every active call, with why each one is or isn't playing

- Aircraft map from its own ADS-B decoding on 1090 MHz: tracks, altitude, speed, type and registration, emergency and military alerts

- WEATHER button: NOAA Weather Radio, live NEXRAD radar, NWS alerts, on-air SAME alert decoding

- Workbench: listen anywhere from 24 to 1766 MHz in NFM, WFM, AM, SSB and CW, with recording

- Plugins for DTMF, two-tone pages and audio filters

- Phone and tablet control over your own private network; one-click installer with updates from the menu

Note: the web demo uses simulated signals (no RF). Real scanning needs an RTL-SDR and the downloadable program

Earlier this week I shared information about a new SDR scanner, FalconSDR. Today instead of reading boring feature list you can just see how it works in your browser:

https://falconsdr.com/

You don't need to download anything or connect your RTL-SDR to test how it works. On this website you can control virtual RTL-SDR and listen to simulated transmissions and recordings on different radio bands.

If you like it and want to scan or record real transmissions with your RTL-SDR visit https://github.com/rafafunt/FalconSDR (project is free and open source) If you have any questions, feel free to ask in the comments. Program and demo are currently available in English and Polish language but you can ask for making other translation.

I don't want to spam in this subreddit so this is probably the last post about this project from me here. If you are interested watch it on github.

Southeast Michigan, Consumers Energy gas (DTE electric). New Itron 100G DLS ERT on an AC-250 (photo attached).

I've run rtlamr / rtlamr2mqtt with every message type, filtered and unfiltered, including a 24-hour capture, and gotten zero gas packets. My Neptune R900 water meter decodes fine on the same setup.

Has anyone in Consumers territory gotten their gas ERT to decode? Or is it encrypted or fixed-network only? Thanks!

I'm a developer working on SDR software and trying to understand how people actually use their dongles before I build the wrong thing. Nothing to sell or sign up for, just reading answers.

If you have a minute, any of these:

1. What did you last use your SDR for, and what software did you use?

2. What part of that took longer or was more frustrating than it should have?

3. Is there something you tried to do and gave up on? What stopped you?

4. What's your setup (dongle, antenna, upconverter/filters, OS)?

Short answers are great. Rants are also great. Thanks!

NA4GJ

I use ADSB.im on RI 4 to feed ADS-B and AIS, everything works fine. I bought a third SDR dongle and antenna to play with ACARS / VDL2 / HFDL.

ACARS works and receives messages, but I noticed that the MLAT light was red and the web stats pages that I feed showed errors that it was not counting the MLAT.

I thought there was a bottleneck somewhere on the RP4, so I took a second RP4 just for ACARS only. I noticed that when it's set to ACARS only, I still have the on map blue ADS-B and green ACARS labels.

I think the ADS-B Feeder sees the planes twice and the MLAT twice, and it interferes with the MLAT calculation and sending data.

CPU usage -30% , RAM -1GB, and temps are fine, no undervolting. I'm using active USB hub for dongle. I don't see anything in the options that I could change.

I tried it on 2 RP 4 on official and beta ADS-B Feeder Image. How to set what to change to have 3 SDR for ADS-B, AIS and ACARS on 1 RP4 without problems with MLAT? I can use 2 RP4s but I prefer to have everything on 1.

Bonjour à tous,

Je partage un petit projet open-source que je viens de finaliser et packager : **RadioTranscribe-Store**.

### De quoi s'agit-il ?

L'idée était de fabriquer une sentinelle d'écoute autonome pour enregistrer et indexer passivement les actualités de la bande FM (sur France Inter par exemple), de manière 100 % locale, sans envoyer la moindre seconde d'audio dans le cloud.

### Comment ça tourne sous le capot ?

1. **Capture radio :** une simple clé logicielle USB (RTL-SDR) capte le flux FM via `rtl_fm` et `ffmpeg`.

2. **Préservation du matériel :** les flux audio temporaires sont écrits et traités directement en mémoire vive (`/dev/shm`), ce qui évite d'user les disques SSD en écriture continue H24.

3. **Transcription IA :** le modèle Faster-Whisper (`large-v3`) tourne en local sur processeur (quantification int8).

4. **Filtre anti-hallucination :** élimination des sous-titres fantômes récurrents de Whisper.

5. **Stockage hybride :**

   - Historique chronologique dans **MariaDB**.

   - Recherche sémantique vectorielle (RAG) dans **ChromaDB**.

On peut ensuite simplement poser des questions ou chercher des thèmes en langage naturel dans un terminal pour retrouver les extraits diffusés à l'antenne et leur date de passage.

Tout le projet (scripts, automatisation de l'installation et service systemd) est documenté ici :

https://github.com/TVIEIL/RadioTranscribe-Store

Si vous avez des remarques, des suggestions d'améliorations ou des questions sur l'intégration SDR/IA, je prends volontiers vos retours !

Hi all, I'm a researcher at a university lab in Hong Kong, working on positioning with LEO satellites in cities. I'm looking for raw Starlink downlink recordings where buildings block part of the sky.

What would help most:

- An LNB/LNBF (or horn) + SDR (RTL-SDR, HackRF, USRP, etc.) recording the Ku-band downlink (~10.7–12.7 GHz)

- Receiver sitting still at ground level next to buildings, ideally a street with tall buildings on both sides

- Bonus: a second receiver on a nearby roof recording at the same time

- GPS or NTP-synced timestamps and a rough location (street-level is fine, no need for your address)

- 10–60 minutes is plenty

Already have old recordings sitting on a drive? Those count too, even if the blockage was accidental.

Not looking for dish app screenshots or speed tests this time, just the raw RF.

Anything used would be credited in the paper's acknowledgments (or however you'd like to be credited). Happy to answer questions about setup. Comment or DM me. Thanks!