HF Spectrum Monitor Technical Information
Location : Central Southampton, UK
This website offers a live view (see links below) of the HF Spectrum seen on a wideband HF receiver connected to a web server via control and graphing software. The receiver offers an instantaneous snapshot of the full 0 to 30 MHz HF spectrum, as well as continuous filtered data from one of its 4 narrowband tuned channels.You may select a section of the wideband and set the frequency and bandwidth of the narrowband channel. Spectral displays can be viewed in your browser in real time.
Main Viewer HTML + JavaScript Viewer Flash Viewer (with live AM demodulated MP3 audio clips)[To see if you have the Flash Player (9,0,45,0 required), click here] [To download the latest Flash Player click here] (install notes) Queries and suggestions may be sent to  |
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A separate 24 hour zoom-able waterfall display shows a chosen section of the spectrum built up from snapshots taken at 2 minute intervals over the last 24 hours. Fully zoomed resolution is approximately 380 Hz / bin (windowed).
24 Hour Waterfall Viewer Flash Viewer |
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Hardware and software details
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The HF Spectrum Monitor is based around a custom Digital Wideband Receiver. This digitises the antenna input using a 16bit ADC at 80 MHz, providing a wideband signal snapshot together with four 48kHz narrowband tuned outputs. The receiver output is via high speed USB2. |
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The receiver is connected via USB2 to a 1U SuperMicro rack server (Dual Core2 Intel® Xeon™ 3060, Dynatron P37G fan). This allows multiple users to view the wideband spectrum, and each user may tune one narrowband channel to enhance the wideband spectral plot or provide audio output. The server runs SUSE Linux and serves its status pages via a redirect from the main web server holding this content. The connection to the internet is via 4 Mbit ADSL modem / router. |
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The antenna is a 1.1m active loop made by
Wellbrook Communications.
It is mounted on a vertical metal pole (also used for a washing line) around 2.5m above the ground.
Software is written in "C". A data collection process runs continuously, saving sections of wideband and narrowband data to temporary RAM files. All images are produced using the GD library in PNG format on demand from the user's web browser. The main web page contains dynamic HTML or Flash viewers that display these graphs and allow receiver control. |