Spectra HF DF  is an HF monitoring and DF system designed and engineered by CommsAudit.  Using our own CA7814 HF receivers the system is capable of providing Super-Resolution Direction Finding (SRDF)across the HF Spectrum from 9 kHz—32 MHz.

Associated with the wideband DF resource are controls for configuring automatic signals detection. Spectra currently supports automatic signal detection using either an absolute threshold or noise-riding threshold. Automatic signal detection can be run against the entire HF spectrum in real time.

Clearly, the HF spectrum incorporates many signals which are not of interest, for this reason, the software incorporates features to target signals based on frequency, signal type and direction/area of interest.

To enable the collection of signals on specific frequencies of interest, the software incorporates our Priority Frequency List, which provides the means to run detections against specific frequencies of interest. To aid subsequent analysis of the collected data, user defined labels are added automatically.

To further refine the targeting of signals of interest, the software incorporates a Signals of Interest list, where the operator can define the signal types the system is required to collect. To achieve this the software incorporates modulation classification and signals recognition. The system utilises the signals classification/recognition to automatically check if a detected signal matches the required signal criteria. Advanced operators can develop their own signal recognisers. When a signal is detected which matches the signal of interest list, the event will be visible in the event manager. Events relating signals which do not match the criteria will be hidden by default, but viewable if required.

In order to provide monitoring and SRDF the system uses an 8 antenna array configuration.  A typical array layout would be a circular pattern of two concentric circles spaced 30m and 100m from the central point and is calculated and spaced to ensure optimum performance.  However,  this is configurable depending user requirement and available real estate.

The antenna used are a cross-loop design including a monopole antenna.  This combination provides excellent results for ground-wave, low take-off-angle sky wave and high-angle and near vertical incidence skywave (NVIS).

The crossed-loop antenna is circularly polarised for high-angle signals, reducing the susceptibility to ionospheric fading and making the antenna performance independent of the orientation of the transmitting antenna. The monopole elements provide excellent performance for long-range skywave.

The advanced techniques in SRDF enable accurate DF within a congested environment where there are multiple co-channel transmitters on a signal of interest. Using CommsAudit’s propitiatory SRDF software an operator can gain a much clearer picture of HF spectrum by obtaining separate lines of bearing towards co-channel emissions.

Spectra HF DF is typically  installed as a fixed site strategic capability.  However, dependent on user requirement the system can be tailored in order reduce the overall form factor and antenna  configuration.  This agile approach means the user has the ability  to deploy a  tactical level  HF DF system rapidly to a static or semi-static location in order to meet the increasing operational need against the HF spectrum.