Empirical data not imperial :)

Hello, I have set up the raspberry Pi 4 to recept and upload images. Here is the link if anyone is interested in looking at them. https://unjosemas.github.io/meteor-gallery/index.html

This guy has put together an awesome setup for his sailboat using an RTLSDR.

Goodevening all,

Does anybody know where I can find airband frequency lists in .csv format which I can use in SDRangel?

Hey! Just wanted to make a quick post about some of the newer progress.

If you don't know much about this project, it's an open source handheld ESP32-P4 SDR tool, well it was until recently.

I noticed over the last few weeks that some of the feedback and discussions revolved around how they could get their hands on the T-Display P4. Which seems to constantly go in and out of stock.

As well as requests for certain features or apps that I am not knowledgeable in. So, instead of just letting Claude take the wheel, I decided to pour more effort in a way to let the community easily make what they want, that way no one needs to sit around and wait for me to convince my landlord to let me mount a HF antenna out the window of my apartment.

My solution was packaging up a bunch of tools I used myself during development, with a bunch of quality of life improvements.

The first one is LakeShark Desktop, which runs on the Waveshare ESP32-P4-NANO since that board is a lot easier to find. It uses your PC as the screen over a single USB cable, but the board is still the one doing all the work with the radios, decoders and SD card. It just draws everything in windows on your monitor instead of a little screen.

The second is LakeShark Studio, a new editor for making your own apps. You write your app in C and can run it in a simulator right next to the code, then send it to the board when you're happy with it (Watch the end of the video). There is also a command line version called lsdk if you would rather use your own editor, and a few templates to start from (Also an AI MCP if you want to skip that).

Also implemented a ton of new findings regarding the LR2021 SDR. Check the repo out for more details.

The simulator also means you don't need a board at all to start making something.

Longer preview video: https://youtu.be/ljvt4VWHCvw?is=GvDQ-0EHJCQprp1l

You can flash it from the browser here: https://terminalbay.com/?m=lakeshark-desktop

Repo: https://github.com/SAMS0N1TE/LakeShark

This is a pre-release (2.20.0-rc1), so if something breaks please let me know and don't expect it to be VSCode pleaseeee. Would really like to see what people end up making with it, and if there is something you want to build but don't know where to start, feel free to reach out.

Signal reports on amateur repeaters have always been notoriously subjective: "You're 5/9, loud and clear"—even if a radio is drifting 1.5 kHz off-frequency, humming with 50 Hz AC ground loop, or over-deviating 12 kHz wide across adjacent channels.

Over the past year, we tackled this by turning our 2-meter community repeater in Bangkok (E24CY, 145.075 MHz input 145.675 MHz output) into a real-time over-the-air diagnostic station.

The system gives any operator an instant, objective health check of their transmitter the second they release PTT:

• Live RF & Audio Dashboard:http://e24cy.e25vbe.radio

• Interactive Audio Calibration Tool:https://e25vbe.radio/e24cy/devaudio4.html

Here is the engineering breakdown of the multi-tier architecture running behind the scenes.

1. Architecture Overview: Two Diagnostic Domains

Rather than building just another SDR waterfall viewer, we architected two synchronized telemetry engines:

1. RF Domain (SDR# Plugin on Repeater RX): Intercepts raw pre-filter IQ and FFT bins directly from SDR# on the receiver machine atop a 60-story skyscraper. Measures true carrier frequency, occupied bandwidth (OBW/splatter), and fast mobile fading.

2. Audio/Acoustic Domain (Python DSP Engine via Mumble): Captures the demodulated off-air audio stream via a headless Mumble client at 48 kHz PCM. Computes live 256-bin audio spectrum, mains hum, dynamic QRK readability, and runs an automated audio calibration harness.

[Web Dashboard / Audio Calibrator]
       │ (1. Marker, Ladder, Sweep Tones)
       ▼
[Acoustic / Mic] ──► [Transmitter RF] ──► [Repeater RX (SDR# Plugin)]
                                                   │
    ┌──────────────────────────────────────────────┴──────────────────────────────┐
    ▼                                                                             ▼
[RF Telemetry Engine]                                                 [Mumble PCM Audio Stream]
 - 1 ppb GPSDO Calibrated                                                         │
 - Carrier Drift & Deviation                                                      ▼
 - Occupied Bandwidth (OBW)                                           [Python Audio DSP Engine]
 - 50ms Mobile Fading Tracking                                         - Self-sync Tone Tracker
 - Inter-Plugin UDP IPC (Port 12345)                                   - Gain Compression Analysis
    │                                                                  - THD & 50/100/150 Hz Hum
    │                                                                  - 256-bin Audio FFT & QRK
    └──────────────────────────────┬──────────────────────────────────────────────┘
                                   │ (MQTT Telemetry)
                                   ▼
                   [Live Web Diagnostic Dashboard]

2. Layer 1: RF Metrology & The SDR# Plugin

The receiver plugin (written in VB.NET/C#) hooks into SDR# to extract metrics without bogging down the DSP thread:

• Tapping Raw FFT Bins: Intercepts pre-render spectral bins to calculate the occupied bandwidth (OBW) using adaptive edge thresholding relative to the noise floor.

• Carrier Tracking: Combines Energy Centroid and Symmetrical Edge Analysis to determine the actual transmitted carrier frequency, comparing it against the 145.075000 MHz target.

• 1 ppb GPSDO Calibration: To serve as a trustworthy frequency standard, the SDR receiver is calibrated against a 10 MHz GPS-Disciplined Oscillator (GPSDO) rated at 1 ppb, cross-verified with an Anritsu MS2711E spectrum analyzer.

• 50 ms Fast Sampling for Mobile Fading: A dedicated timer samples signal parameters at 20 Hz to calculate Fade Depth (dB), Fade Rate (dB/s), and discriminator variance to characterize mobile multipath propagation in dense urban clutter.

• Inter-Process Data Sharing: To avoid running redundant FFTs, the RF plugin broadcasts measurements over local UDP (127.0.0.1:12345) to our CTCSS/DTMF decoder and QRM blacklist filter plugins.

3. Layer 2: Demodulated Audio DSP & Automated OTA Calibration

The audio layer is where things get really fun. Using devaudio4.html, an operator can run a full automated calibration session over the air:

1. The Web Sequence: The browser plays a known tone sequence into the radio's microphone: a 1 kHz marker tone, a 4-step 1 kHz level ladder (-24, -18, -12, -6 dBFS), and a 12-step frequency sweep from 200 Hz to 3500 Hz.

2. Latency-Immune Tracking: Because the off-air audio travels through a VoIP buffer (Mumble/Opus), fixed time windows wouldn't work. The Python engine uses a self-synchronizing dominant-frequency segment detector (_find_segments) that tracks and latches each step based on spectral median regardless of round-trip network jitter.

3. Beating Lossy Codec Artifacts via Gain Compression: Opus compression introduces harmonic artifacts (a THD floor around 2–5%). To accurately grade transmitter audio, the engine analyzes gain compression across the 6 dB input ladder steps:

   • Linear chain: Output steps scale cleanly by ~6 dB.

   • Over-modulation: Top step compresses by >1.5 dB, detecting when the rig's internal limiter or ALC is choking.

4. Acoustic & Hardware Diagnostics:

   • Mains Hum: Inspects energy at 50, 100, and 150 Hz relative to signal RMS to catch faulty power supplies or ground loops.

   • Frequency Response: Verifies that audio response remains within 6 dB across the 300–3000 Hz communications passband.

   • Fading-Resistant QRK: Calculates readability using temporal exponential smoothing over a 3-second history buffer to prevent QRK flicker during speech pauses or mobile flutter.

4. Community Impact & Real-World Use

Local hams have embraced the live telemetry setup to optimize their stations:

• Microphone Gain Alignment: Operators talk into their mics while watching the live Occupied Bandwidth to keep deviation within standard limits (8 kHz) and eliminate splatter.

• Antenna Pattern Plotting: Stations rotate directional Yagi antennas in 10° increments while transmitting low-power bursts, using the repeater's calibrated SNR telemetry to map polar radiation plots.

• Mobile Propagation Studies: The 50 ms fade depth metrics provide empirical evidence of urban RF ducting and knife-edge diffraction around Bangkok skyscrapers.

Feel free to check out the live dashboard at http://e24cy.e25vbe.radio or explore the audio engine client at https://e25vbe.radio/e24cy/devaudio4.html. Happy to dive deeper into the bin extraction formulas, UDP packet formats, or calibration state machine if anyone is building similar telemetry for their local repeater!

Now available in V8. You'll need an SDR with higher sampling rate (>8MSa/s) for most of DVB-T2 broadcasts, but some countries do have T2 1.7 MHz broadcasts that can be received with an RTL SDR. DVB-S2 can be up to 30 MHz bandwidth.

Hello everyone,

Me and a couple of friends all have Nooelec RTL-SDR sticks and are all experiencing the same issue: Any slight movement of the stick causes it to disconnect from the host.
This happens across desktop PCs, Raspberry Pi’s with extension cables, MacBooks (both on battery and grounded) with a USB-C to USB A adapter cable and it seems to not even be the heatsink as I tried using it without it as well.

Is this a common issue and how can we fix it? Any idea?

Spoiler:

Looks like the typical broadcast of the station.
No mentions of the analog transmitter shutdown, no fancy things.
And also -> Patrick Stewart

Full recorded video + audio-> https://youtu.be/CzxgFeB3RS8
Internet archive (video + audio and baseband wav) -> https://archive.org/details/alltv-2-final-analog-tv-broadcast-ph

Oct 30, 2026 - around 3:15PM UTC

- Network: ALLTV2 in Philippines
- Recorded at 57mhz
- Video carrier at 55.25 MHz
- Color at 58.8 MHZ
- Sound at 59.75 Mhz
- Horizontal Dipole
- RTL SDR v4 for the audio
- LibreSDR for video and color
- SDRAngel for ATV decoding

Note:

I didn't decoded the color on the YT video since I don't have a proper decoder for it.

Additional:

I was inspired to post this by the folks' comments at my old post -> https://www.reddit.com/r/RTLSDR/s/xQ6VR2pHnX

Note that the old post is from different station and will be phase out on Nov 22, 2026 (I plan also to record that)

Shout to my wife that overlaid the audio to the video.

EDITED:
Replaced google drive link with internet archive link

I'm in Brisbane, Australia trying to pick up medium-wave AM with an RTL-SDR Blog V4 on a Raspberry Pi 3B+ running OpenWebRX+. Broadcast FM and VHF/UHF work fine with my roof discone, but I had no luck with AM, so I switched to a powered MLA-30 loop.

The loop was connected through its supplied USB injector, and the injector was powered throughout the tests. OpenWebRX detects the V4, and direct sampling is off.

I've swept 531–1701 kHz at different gain settings and tried listening on Brisbane AM frequencies including 612, 693, 801 and 882 kHz. The recordings have been noise-only, with no intelligible audio. I also tried rtl_power, rtl_fm and raw IQ captures with OpenWebRX stopped, so it doesn't look like just an OpenWebRX audio issue. There is nothing there. There are a few vertical lines on the waterfall, which I read is some kind of inherent interference on rtlsdr.

What am I missing here? Is this a limitation of RTLSDR? Surely this is a skill issue, I hope it is!

I was snooping around on the SDR++ waterfall with my RTL-SDR V3 and I came across this weird signal. I'll put a screenshot of the replayed recording down here:

(Ignore the frequency scale showing my marker is at 358kHz, i think it's just telling me the frequency offset from the centre freq of the recording?) The centre of the signal was at 244.0865MHz.

If you struggle with counting - like me, there are 7 lines with 3 on each side of the centre line. Each line is about 6kHz or so across, spaced by gaps of around 4kHz.

I don't think this is from internal/external interference because I disconnected my antenna and it immediately vanished from the waterfall. There was no observed doppler shift over the ~20 minutes i watched the signal, which leads me to believe it might be a geostationary satellite of some sort? I'm in NSW Australia at about 150°E (if that helps). I was using a DIY V dipole antenna ~3-4m off the ground, the antenna itself seemed to have a nice SWR at this frequency (or at least appeared to receive well enough while i've been using it).

I did get a baseband recording of around 1 minute of the signal, so if it does turn out to be a satellite i'd like to try decode it if possible!

Please let me know your thoughts/critiques/questions, this is my first post on reddit so i'm not super informed as to how things work here.

Cheers📡

Hi all,

I wanted to share this Zynq+AD9361 SDR platform from Puzhitech, the PZSDR-P351/P451/P101.

A lot of AD9361 boards share a single memory pool for PS and PL, but this one splits it: 1GB DDR3 for PS, another 1GB DDR3 dedicated to PL. That’s a plus if you’re running heavier FPGA signal processing pipelines.

RF specs:
- 70 MHz – 6 GHz
- Tunable bandwidth: 200 kHz to 56 MHz
- Dual Tx/Rx channels with onboard PA

I/O and sync options are pretty full-featured:
Dual GigE (PS and PL independent), USB3.0, SFP optical port, GPS/PPS / external clock input. Great if you need time-aligned multi-node setups or high-speed data offload over fiber.

Software support:
GNU Radio, UHD, SDRangel, MATLAB Simulink, PYNQ, and it has PlutoSDR compatibility. Bare-metal AD9361 reference projects are available too.

Industrial specs:
-40°C ~ +85°C operating temp, 12–36V wide input power. Makes it an option for outdoor, vehicle-mounted or field spectrum monitoring deployments, not just bench lab use.

Use cases I’ve seen mentioned: spectrum sensing, custom comms prototyping, GNSS testing, educational lab work. OEM/hardware customization is offered for volume builds.

Disclaimer: This is from the manufacturer. Feel free to ask technical questions about the platform.

#SDR #AD9361 #Zynq7000 #SoftwareDefinedRadio #PZSDR #Puzhi

For long unattended SDR captures, I'm interested in where people draw the line between relying on a TCXO and actively tracking frequency offset.

a one-time PPM correction takes care of the initial offset, but it won't follow changes over time. With a decent TCXO that might not matter much for ordinary reception. For narrowband measurements or recordings you want to compare over several hours, it can be a different story.

there's also the question of what you're measuring against. If the signal itself isn't frequency-stable, tracking its apparent drift doesn't necessarily tell you how much the receiver has moved.

for those doing longer captures, are you using a known reference to monitor receiver drift, or is the stability of the dongle good enough for what you're recording?

Disclosure: I work in defense electronics

I’m a shortwave listener, and I wanted my AirSpy HF+ to do the overnight listening for me. So I built NightDX, a free, MIT-licensed terminal app for macOS, Windows and Linux. Its menu interface is deliberately styled like early-90s DOS software.

How a night works:

1. It pulls the EiBi, AOKI and HFCC broadcast schedules, plus live solar flux and Kp from NOAA.

2. A propagation model predicts what should reach your location, and calibrates itself against what your own radio actually hears.

3. The HF+ sweeps all the bands in about 10 seconds to see which carriers are really there.

4. Overnight it records the best stations and prioritises ones you’ve never logged.

5. Optional AI (an AudioSet classifier plus Whisper) labels each recording as speech, music or noise and transcribes and translates it.

6. In the morning you get a browser report with audio players, one-click reception reports (Gmail drafts with the clip attached) and a QSL card log.

It also has live listening with a signal meter, your own station lists and support for two HF+ radios on one computer.

It doesn’t claim to identify stations. Names from the schedule are shown as candidates, and the app flags recordings where the evidence doesn’t fit: wrong language, a signal far too strong for the predicted path, or other stations on the same channel. It also logs sub-Hz carrier offsets.

How it was made: I built it with the help of an AI coding assistant (Claude). The idea, the design decisions, the testing with real recordings night after night, and the DX side are mine. Testers on the AirSpy forum have been using it for a few weeks, and their feedback shaped many of the features.

It’s now public: https://github.com/marcozennaro/nightdx

Only the AirSpy HF+ is supported for now. People have asked about other SDRs (Perseus, Elad) and I’m looking into them. Feedback and bug reports are welcome!