2003 Ninth International Conference on HF Radio Systems and Techniques

Meaningful impedance measurements of short HF antennas can be performed with a set-up consisting of an automatically sensing high power generator, combined integral reflection meter, tuneable preselection filter and a remote field probe. These are combined as a customised vector network analyser. The idea is to avoid measuring equipment destruction by using an automatic adjustment of test port pow... View full abstract»

The area of digital communications has undergone a significant transformation in the last ten years due largely to the discovery of turbo codes. The "turbo" concept can be applied to more than just forward error-correction (FEC) schemes. For example, waveforms developed for the high frequency (HF) band typically place an interleaver between the FEC scheme and the transmitted symbols. The purpose o... View full abstract»

Transmission in the high frequency (HF) band is considered not to be reliable, due to channel's highly dispersive characteristics, frequency selectivity, Doppler spread and multipath propagation. Briefly, it can be stated that all inconveniences of a wireless channel are present, making this channel a very hostile environment. Some innovations used in presented HF modem design are described. Ortho... View full abstract»

STANAG 4538 defines a third generation (3G) HF system that includes a synchronous Automatic Link Establishment (ALE) system coupled with efficient data link protocols. The data link protocols, collectively known as XDL, have been integrated into the Harris RF-5800H HF man-pack radio system and are included in the Harris radio being produced for the UK BOWMAN program. This paper begins with an over... View full abstract»

RF sky wave transmissions undergo multipath fading due to propagation through the ionospheric layers. The HF channel is time varying and can be modeled by a tapped delay line of independent complex fading processes each exhibiting correlated fading characteristics specified in the ITU-R recommendation. A practical configuration for a turbo equalizer to combat the effects of intersymbol interferenc... View full abstract»

Uses the GICCA categorisation model, which was developed by Carkhuff and Berenson (2002) to analyse the maturity of products and services. Highlights and explains some of the innovations in the hobby and to provide a framework for looking to the future. View full abstract»

Harris Corporation has incorporated its implementation of the STANAG 4538 automated radio control system (ARCS) protocols into its RF-5800H and AN/PRC-150(C) manpack radio products, and is now offering this capability as a standard feature of these radios. In developing this implementation, Harris has developed extensive experience in use of these protocols under a variety of operating conditions.... View full abstract»

High frequency (HF) coverage planning tools have been used successfully for many years to assist radio planners in designing HF networks and operating HF services. This paper describes techniques which have been derived as an adjunct to existing planning tools to improve their utility for use with modern HF systems and networks. The techniques factor in real-time frequency diversity and site diver... View full abstract»

Digital Radio Mondiale (DRM) is a new transmission standard designed for broadcasting in the traditional AM bands below 30 MHz. The system was officially launched at the World Radio Congress in June 2003, after which permanent digital broadcasting in the AM bands will begin. Quality of service in digitised AM bands (QoSAM) is a collaboration between QinetiQ, Thales Broadcast & Multimedia, VT Merli... View full abstract»

This paper presents results of an investigation into the change in the utilisation of the HF spectrum over a sunspot cycle, using experimental occupancy measurements made at Linkoping (Sweden), and at Baldock (UK). This is a companion paper to "Models of HF spectral occupancy over a sunspot cycle" (see L. V. Economou et al., ibid. (2003)). View full abstract»

The main objective of the present design has been the development of a HF band communication system providing digital voice transmission within around 3 kHz bandwidth, through ionospheric reflection, mainly, but not only, for aeronautical environment. Interactivity, as a basic design constraint, has shown that standard structures using single carrier modulations are not suitable at all because the... View full abstract»

We use our 'wideband-Q' method of finding and measuring the various resistance components of a small tuned loop (Underhill and Harper, IEE Electronics Letters, vol.38, no.18, p.1006-8) to measure and assess a variety of small HF tuned loops. The method relies on bandwidth, and hence Q, measurements being made over the two to three octave tuning range of such tuned loop antennas. Because the measur... View full abstract»

In a multi-carrier transmission system, intermodulation distortion (IMD) is generated because of amplifier non-linearities. The presence of IMD degrades the performance of such systems. In this paper, an IMD cancellation technique based on phase shift is presented. The technique depends on applying pre-determined phase shifts to each carrier signal before they are combined. Then, an increased numb... View full abstract»

The move from analogue to digital HF broadcasting using the Digital Radio Mondiale (DRM) standard poses some problems of transition that have not been present for the transition of other digital broadcasting systems most notably that there is little or no additional spectrum available to support the simulcast period when both analogue and digital transmissions will coexist. This paper explores the... View full abstract»

Access to the Internet is considered essential and critically important to sustainability of rural economics and social development. Most rural communication centres, such as community telecentres (CTC) urgently need an error free long-haul digital radio link connection. Provision of an affordable and reliable narrowband radio link becomes essential to help them with their economic issues. The HF ... View full abstract»

Rockwell-Collins France has completed during the calendar year 2002 the software development of an IP client for the product line HFMessenger™ that is compliant with STANAG5066. STANAG5066 is a new ratified NATO standard that defines a profile for high frequency radio data communications. The key features of this standard are the definition of a selective ARQ mechanism and the use of high pe... View full abstract»

A new network of transmitters and receivers has been installed in northern Scandinavia (including Svalbard), capable of measuring the time delay and Doppler spread characteristics and the directional structure of received signals on three HF paths. Based on the large amount of data expected from this experiment, a statistical classification of signal directional characteristics under various geoph... View full abstract»

Observations over recent years have established that large scale electron density structures are a common feature of the polar cap F-region ionosphere. Whilst experimental work has produced many useful results (Warrington, E.M. et al., IEE Proc. on Microwaves, Antennas and Propag., vol.144, p.241-9, 1997; Rogers, N.C. et al., IEE Proc. on Microwaves, Antennas and Propag., 2003; vol.144, p.91-6, 19... View full abstract»

The HF band is challenging - having mobility and unpredictability at its heart. This paper focuses on the spectral implications of the first frequency translation in a receiver, or the corresponding final conversion in a sender. The aim is to optimise the internal frequency plan of the radio, i.e., the tuning range of local oscillator, filtering, etc. EMC compromises in that area will be the last ... View full abstract»

Measurements of the time-of-flight and direction of arrival are presented for an HF radio signal on a subauroral path between Sweden and the UK. During the day, the signal usually arrives from the great circle path (GCP) direction. However, at night, especially during winter and equinoctial months, the signal often arrives at azimuths displaced from GCP. To the north, signals are probably scattere... View full abstract»

This paper focuses on the use of reconfigurable analogue technology to support multi-standard Digital Radio Mondiale (DRM) and high frequency (HF) communication systems. The choice of receiver architecture is discussed within the context of frequency adaptive systems and the low-IF receiver is introduced as an alternative to the zero-IF digital receiver. This paper also investigates the ability of... View full abstract»

The proposed method, based on a generalization of the Γ-match concept, allows an almost instantaneous computation of aircraft towel-bar antenna self and mutual input impedance by a 2D electrostatic analysis and fast numerical simulation of the aircraft without antennas. Application to test cases has shown results in good agreement with reference solutions (better than the one proposed by oth... View full abstract»

The BOWMAN HF networking solution is based on easing the integration of the RF-5800H radio into the BOWMAN network using a concept called bridging. This has greatly simplified the IP management problem associated with the HF subsystem. The HF Networking scheme utilizes the STANAG 4538 capabilities in association with performance enhancing technologies such as concatenation and compression to achie... View full abstract»

This paper describes an experimental evaluation of small (h<λ/100) wire transmitting antennas for amateur radio applications at 136 kHz and 73 kHz. Efficiencies between 0.0033% and 0.13% are obtained, whilst the radiation pattern is found to be that of a short monopole. Causes of low efficiency, and discrepancy between measured and calculated field strengths are discussed. View full abstract»