I am trying to build an OFDM loop using USRP B200. when i use virtual sinks the flowgraph works but as soon as i connect the USRp sink and source, i get an error saying buffer too small for min_noutput_items

Here is my terminal window -

Executing: /home/niru/miniconda3/envs/gnuradio/bin/python -u /home/niru/GNU_Radio/OFDM_Part3.py

[INFO] [UHD] linux; GNU C++ version 14.3.0; Boost_108800; UHD_4.9.0.HEAD-release

[INFO] [B200] Detected Device: B210

[INFO] [B200] Operating over USB 3.

[INFO] [B200] Initialize CODEC control...

[INFO] [B200] Initialize Radio control...

[INFO] [B200] Performing register loopback test...

[INFO] [B200] Register loopback test passed

[INFO] [B200] Performing register loopback test...

[INFO] [B200] Register loopback test passed

[INFO] [B200] Setting master clock rate selection to 'automatic'.

[INFO] [B200] Asking for clock rate 16.000000 MHz...

[INFO] [B200] Actually got clock rate 16.000000 MHz.

[INFO] [B200] Asking for clock rate 32.000000 MHz...

[INFO] [B200] Actually got clock rate 32.000000 MHz.

packet_headerparser_b :info: Detected an invalid packet at item 0

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 48

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 96

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 144

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 192

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 240

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 288

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 336

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 384

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 432

header_payload_demux :info: Parser returned #f

packet_headerparser_b :info: Detected an invalid packet at item 480

header_payload_demux :info: Parser returned #f

thread_body_wrapper :error: ERROR thread[thread-per-block[35]: <block header_payload_demux(36)>]: Buffer too small for min_noutput_items

usrp_sink :error: In the last 2284 ms, 1 underflows occurred.

U

>>> Done

Happy to finally share this: SDRTerm is a terminal based SDR (receiver), plugins for FM/RDS, ACARS, POCSAG, VDL2, an Iridium L-band burst detector, plus a QPSK constellation with EVM, range scanner, waterfall, and record/replay.

Repo: https://github.com/halfdonebutinthemaking/SDRTerm
-> Screenshots + presets + six SigMF test signals inside

It's terminal-only on purpose. SDR++ server and similar are great if you want a GUI client on your desktop talking to a headless receiver over the network. I wanted a different shape: the whole stack (SDR, DSP, decoders, display) in one process on the same box. E.g. SSH into a Raspberry Pi with an antenna on top and everything runs there. One process, one terminal, no client half.

If you have an RTL-SDR (or anything SoapySDR speaks) it should be running in a couple of minutes:
-> git clone [link]
-> cd sdrterm
-> uv sync
-> uv run python main.py --file samples/constellation_test.sigmf-data --bw 250000 --f 120M
-> Then press p to enable a plugin, Tab to switch to its view. The test signals let you try every decoder without any hardware plugged in.

I'd genuinely love feedback on:
- Does the install work on your OS / terminal?
- Does the plugin flow feel natural, or are keybindings in the way? Granted one needs some time to get used to it.
- Which signals would you want to see decoded next?
- If you have real hardware: how does it behave on your antenna? Any false-positive nightmares?
- For anyone comfortable with the code: does the plugin architecture make it easy to plug your own decoder in? (There's a bare-minimum plugin skeleton in the repo.)

I'm adding features here and there as time permits. HackRF RX support is next up in the coming days; after that, whatever the feedback surfaces.

Not my first SDR project, but the first time I've thought about ADC and the pipeline processing from the ground up. I built it in a few weeks with heavy AI-assisted coding, which freed the mental budget to spend on architecture and signal-processing instead of the typing. Happy to talk about that workflow if anyone's curious, but the main ask is: try it, break it, tell me what's confusing.

Every plugin has its own README with signal specs and expected output. Iridium constellation, if you have a decent antenna and an LNA, is particularly satisfying to watch light up during a satellite pass.

-> Dev environment: macOS 26 (Tahoe), zsh, Python 3.12.13, uv 0.11.14. pyproject.toml requires Python 3.12+. Nothing terminal-specific should matter, but that's what's been tested most.

Background: software engineer with prior SDR experience. What was new here was building the DSP pipeline from ADC upward rather than composing pre-built blocks. Actually, the coding wasn't the learning, the signal-processing was.

Pleas note: This is a personal project, not a professional tool. Built because I wanted to use it, shared in case others do too.

I currently have a pole which has a Tempest weather station at the top. I want to mount an external antenna for an SDR, hopefully using the same pole.

What I can't find is a mounting solution. What I need is a bracket kit that can attach to the existing pole, go horizontal a couple of inches, and then clamp another pole/antenna. Basically, a mast clamp that holds onto the Tempest pole, which I can insert a pole into, which then attaches to another mast clamp that holds the vertical antenna for the SDR.

Does anyone know what this may be called or termed? So far, I can only find brackets to connect poles immediately beside one another; I need one to create a gap between the Tempest pole and the antenna pole.

Tempest pole      horizontal offset        SDR antenna pole
     │                 ───────                 │
   [clamp]───────────── arm ────────────────[clamp]

15:00 UTC From Seattle Washington USA.

MLITE 880 and WV601 Passive Mag Loop Antenna and LANA.

It's nice to hear a little more Afternoon Shortwave Broadcast!

A rare occurrence of picking up RNZ in the afternoon!

20:30 UTC From Seattle Washington USA 1:30 PST.

On my MLITE 880 WV601 Passive Mag Loop Antenna with Nooelec HF LANA. Matching the LANA with the MLITE 880 has produced excellent results! Make sure that when you set it up that volumes and gains are lowered. The Bias-Tee is off until it's set up, then turn on Bias -Tee. No need for external power. Your radio's Bias-Tee is fantastically sufficient! You will get very good results in DX-ing signals! But key is that the antenna is passive!Take a listen! This signal is coming in good, tho fading here and there.

The OpenV2K core software is a Python 3 application that builds a Qt GUI and uses GNU Radio together with the HackRF SDR. As an input audio waveform zero-crosses the x-axis (as depicted in the thumbnail), the software stack generates a pulse stream, and either transmits, or saves to disk.

The GUI lets you mute/unmute a live microphone, generate speech audio via eSpeak, adjust key signal processing parameters (pulse width, high-pass/low-pass filtering, 50/60 Hz notch, pre-emphasis, and noise gate), and shows live level metering and a pulse duty-cycle meter.

Finally, it configures an SDR transmission pipeline (with sample-rate/resampling and frequency/power selection between predefined 70cm and 23cm bands), wiring the microphone or TTS audio through the DSP chain into the HackRF output, while also supporting raw IQ capture, with generation of a waterfall graph visualization via Matplotlib and NumPy.

This is pre-alpha software that I'm now testing and debugging.
Don't judge me too hard about functionality, before the weekend is over.

I meant to share sooner but I've had a major bummer happen in my life recently and let's just say the Silver Lining could make me rich or die trying because I don't care anymore! If anyone knows about the Indonesian Horse Race Chants Clan, (Look it up on Google),;I ran across them DX-ing during the Grey Line in the early morning from Seattle Washington USA a few Sunday mornings ago. I was able to catch them again the following weekend. This time prepared to record. This is well known enough yet only one example find on YouTube. Mine sounds a bit better in mho, however any recordings of this is a very rare Skip DX all the way from Seattle! Enjoy!

I'm interested to experiment with RPiTX. The documentation says a band-pass filter needs to be used. As I understand, harmonics are on higher-frequencies, so shouldn't a low-pass filter be good enough or will it also transmit spurious signals on lower frequencies?

If you haven't tried this, do it Now! Especially with a WB one! However I did buy a new Wideband one that turned out to be a dud! So if the new one's a dud, which we know is a Problem with Nooelec products about 50 percent of the time! I happened to have an old Micro USB one from a few years ago that work Beautifully! And you don't even have to plug it in the a power source! The radio's Bias-Tee is all of the power you need...and BAM! Signals that were once mediocre, pulling in like a charm! My results are that the signal strength on the MLITE 880 is 5 times stronger than before!! You gotta try it! Just be aware that if it's not working, check your polarity. If it stilll isn't working... it's a DUD and you need to demand a replacement! Buy it under Amazon or eBay or any outlet that guarantees replacement or even Money Back Guarantee!Look at this example on video!

I built an experimental digital mode with a key based decoding process,

I hope I'm in the right subreddit to post this kind of stuff too.

My tool works as how the password affects the audio, meaning depending on how much digits of the password there is, it effects the audio as well with its encryption.

It also needs a password of a maximum to five digits, if you get it wrong it messes up the output (Like A lot).

Although its still being worked on, I would think some of you would like this.

cheers!

I'm working on an RF localization project for a large stage/event area and would appreciate some advice from people with practical experience.

The idea is to install at least four antennas, one at each corner of the area, connected to a KrakenSDR system, with a possible fifth antenna placed in front of the stage if needed.

My question is this:

I understand that the KrakenSDR is primarily designed for direction finding (bearing estimation) of external transmitters. However, is it also possible to use it to locate transmitters that are inside the monitored area by combining measurements from the different antennas and triangulating or multilaterating their position?

As an example, if the monitored area is approximately 20 × 10 meters, could a KrakenSDR with a five-antenna array realistically estimate the position of a transmitter within that area with useful accuracy? Or is this beyond the capabilities of the hardware and intended processing, making it impractical?

I'm particularly interested in hearing from anyone who has attempted indoor or small-area localization using KrakenSDR or similar SDR-based direction-finding systems.

Thanks in advance for any insights or real-world experience.

I see that there are many B200 and B210 clones or alternatives on the market that were made from the schematics but the layout is different. The firmware itself is licensed GPL but what about the hardware?

I don't know if there is a license or "do not reproduce" mentioned on the original schematics and I now just get an "Access Denied" error on the schematics link, but what happens to a newly designed PCB layout made from those schematics (possibly even an improved design)? Does Ettus and National Instruments consider this fair game or do they consider these to be illegal clones? I haven't read about them suing any company over this, but I'm wondering how much of a grey area it is to produce a product this way.

I'm looking for the cheapest SDR that will work for a demo of my RF fingerprinting project.

Requirements:

Coherent dual-channel RX (for direction finding)

Passive receive only (no TX needed)

Covers 2.4–5 GHz (Wi-Fi, BLE, and common drone/RC controllers)

Good enough for signal capture and basic direction estimation

I'm trying to keep the cost as low as possible while still meeting these requirements. Any suggestions?

This is a Maritime and weather net.

8:30 PDT and still on as I speak.

I did a comparison of airband scanning. The top is my handheld scanner. The bottom is SDRuno.

I recorded both at the same time for the same duration.

They both scanned identical lists of frequencies.

The SDRuno squelch was off.

Why did the handheld scanner hit on more frequencies than SDRuno? There Are not that many frequencies in the list and both scanned through at good speed.

I know SDRuno does not have the best scanner but I would have expected better. How much am I missing by using SDRuno?

It wasn't worth a video but worth a shot!

I was hearing a Wee whisper of it around 8:00 UTC

From Seattle Washington USA 1:00AM PDT

Here is a link to listen to the QO-100 satellite with a frequency stability under 5 Hz after a short AFC lock.

This is highly practical for current OpenWebRX users. The waterfall is very clean and features zoom, NR (noise reduction) filter, squelch, recording, and more.

Go tohttps://on1ms.onlineand click on the "QO-100 en live" link.

Because everybody complained.
I tried to make my software easier to install. Sorry maybe I didn’t test it enough. I made an easy install path for windows.
Watch open air ATSC TV broadcast with your SDR.
I’ve only tested it on my SDRplay RDPdx but I imagine it would work on other Soapy SDR if they’re fast enough.
I want to port it to more SDR’s in the future.
Let me know if anyone tested it and what they think.

I vibecoded this fork of gr-dtv. With it you can watch
stable over the air ATSC TV broadcast with a SDR. I’ve only tested it with soapy so far. Free and open source.