SDR Television Beta #6
Simon Brown • August 28, 2025
SDR Television
- Improved phase detection at the start of each frame (SOF, PLS) which in turn improves sensitivity.
- Added 2,000 ksps receive, confirmed as working with GB3NQ.
- Sensitivity still not as good as a Serit 4334 NIM as used in the MiniTioune receiver, what's missing is synchronisation timing, I will be using Gardner timing error detection (TED). This will be added in Q1, 2026 when this project is extended for terrestrial use.
Downloads are at the bottom of this page.
About Gardner timing error detection
Gardner timing error detection is a widely used technique in digital communications for estimating and correcting timing errors in the received signal. It is commonly employed in symbol timing recovery circuits, particularly because of its effectiveness even when the carrier phase is unknown or rotating—making it carrier phase independent.
How Gardner Timing Error Detector Works
- Gardner's method operates by sampling the received signal at twice the symbol rate (two samples per symbol).
- The timing error is calculated by comparing the signal sample at the midpoint of the symbol (between two symbol peaks) to the samples at the symbol boundaries.
Zero-Crossing Principle
Gardner's TED is based on a zero-crossing concept—detecting timing errors by observing differences across symbol transitions, not requiring knowledge of the transmitted data. This is known as a non-data-aided approach. If data symbols are known, this becomes a data-aided/decision-directed form called Zero Crossing Timing Error Detector.
Applications and Advantages
- Carrier Phase Independence: It is robust even with phase offsets or frequency drifts, which is essential when the carrier recovery is not perfect.
- Historical Relevance: Gardner timing error detection was notably used in Mariner Mars 1969 missions for symbol synchronization in telemetry receivers.
- Multi-level Modulations: While originally used for QPSK (quadrature phase shift keying), the principle extends to other digital modulation schemes, though modifications may be needed for Nyquist pulses with low roll-off.
Summary of Use
- Gardner TED is popular for timing synchronization in digital receivers, such as those used in wireless communications, SDRs, QAM, and OFDM systems.
- It helps align sampling instants to symbol boundaries for accurate symbol detection, crucial for bit error rate performance.
In conclusion, Gardner timing error detection is a foundational algorithm ensuring precise symbol timing in modern communication systems, prized for its carrier independence and non-data-aided operation.
- https://webdemo.inue.uni-stuttgart.de/webdemos/02_lectures/uebertragungstechnik_2/timing_error_detection/index.php?id=2
- https://wirelesspi.com/gardner-timing-error-detector-a-non-data-aided-version-of-zero-crossing-timing-error-detectors/
- https://wirelesspi.com/on-the-link-between-gardner-timing-error-detector-and-early-late-timing-error-detector/
- https://john-gentile.com/kb/dsp/Timing_Sync-TEDs.html
- https://www.reddit.com/r/DSP/comments/164bvjg/gardner_algorithm_applications_limitations/
Download
This minimum version of SDR Radio is shown below. Only download if SDR Television displays an error message when starting.
SDR Television
Download from either:
- OneDrive: SDR Television V1.0, 64-bit, 2025-08-28_0613.exe
- Dropbox: SDR Television V1.0, 64-bit, 2025-08-28_0613.exe
SDR Radio
Download from either:
- OneDrive: SDR-Radio V3.4, 64-bit, 2025-07-16_1114.exe
- Dropbox: SDR-Radio V3.4, 64-bit, 2025-07-16_1114.exe
Version 1.6.2 This release fixes two bugs in the new DX Spot feature. The spot age logic incorrectly affected spot display. When the map was zoomed, station markers off the map would be displayed at the top left (0, 0). Downloads are on the World Map page . Version 1.6.1 This release fixes two fatal bugs in the new DX Spot feature. When the graphics engine is restarted, resources are correctly released. Fixed a resource leak when processing the MoseMove logic. Downloads are on the World Map page . Version 1.6 This release adds the display of DX Spots. Display spots are submitted to PSK Reporter which in turn are relayed by a MQTT Broker running on a high performance Akamia node. Spot Format Each spot consists of these fields: Sequence Frequency Band Mode Signal level Time stamp Sending station call, square, country Receiving station call, square, country Note: The country is the ADIF country. Spots are displayed as they arrive, currently no on-demand database. Bandwidth To reduce bandwidth from the broker, filtering is required for 80m up to and including 15m. Filtering requires at least one field below to be set in a definition: Receiver callsign, square or country. Sender callsign, square or country. Without filtering the bandwith from the broker could be excessive. For LF and VHF+ no filtering is required due to the lower number of spots sent on these bands. In a later version the bandwidth restriction may be reduced.
Version 1.6.1 This release fixes two fatal bugs in the new DX Spot feature. When the graphics engine is restarted, resources are correctly released. Fixed a resource leak when processing the MoseMove logic. Downloads are on the World Map page . Version 1.6 This release adds the display of DX Spots. Display spots are submitted to PSK Reporter which in turn are relayed by a MQTT Broker running on a high performance Akamia node. Spot Format Each spot consists of these fields: Sequence Frequency Band Mode Signal level Time stamp Sending station call, square, country Receiving station call, square, country Note: The country is the ADIF country. Spots are displayed as they arrive, currently no on-demand database. Bandwidth To reduce bandwidth from the broker, filtering is required for 80m up to and including 15m. Filtering requires at least one field below to be set in a definition: Receiver callsign, square or country. Sender callsign, square or country. Without filtering the bandwith from the broker could be excessive. For LF and VHF+ no filtering is required due to the lower number of spots sent on these bands. In a later version the bandwidth restriction may be reduced.
Version 1.6 This release adds the display of DX Spots. Display spots are submitted to PSK Reporter which in turn are relayed by a MQTT Broker running on a high performance Akamia node. Spot Format Each spot consists of these fields: Sequence Frequency Band Mode Signal level Time stamp Sending station call, square, country Receiving station call, square, country Note: The country is the ADIF country. Spots are displayed as they arrive, currently no on-demand database. Bandwidth To reduce bandwidth from the broker, filtering is required for 80m up to and including 15m. Filtering requires at least one field below to be set in a definition: Receiver callsign, square or country. Sender callsign, square or country. Without filtering the bandwith from the broker could be excessive. For LF and VHF+ no filtering is required due to the lower number of spots sent on these bands. In a later version the bandwidth restriction may be reduced.
SDR Television v1.1 May 18th, 2026: This is the official v1.1 release , code exactly the same as 1.0.16 which has survived testing for a few weeks. Lots of improvements since the last official kit. As with any software project, there's always room for improvements and new features, but for now here's a stable solution which works well with the QO-100 satellite. Many thanks to Sigi and the DATV test team. Downloads are at the bottom of this page.
SDR Television v1.0.14 April 12th, 2026: A new kit, lots of improvements since the last official kit. As with any software project, there's always room for improvements and new features, but for now here's a stable solution which works well with the QO-100 satellite. Many thanks to Sigi and the DATV test team. Downloads are at the bottom of this page.
SDR Television v1.0.9 March 13th, 2026: A new kit, lots of receive improvements since the last official kit. As with any software project, there's always room for improvements and new features, but for now here's a stable solution which works well with the QO-100 satellite. Many thanks to the DATV test team. Downloads are at the bottom of this page.
First Impressions
SDR Television v1.0.6 February 13th, 2026: A new kit, lots of receive improvements since the last official kit. As with any software project, there's always room for improvements and new features, but for now here's a stable solution which works well with the QO-100 satellite. Downloads are at the bottom of this page.
February 10th, 2026 Pluto Correct the FIR filter definitions, this has improved reception.
