RSGB proposal for experimental
amateur radio access to 500kHz

Abstract

A proposal is made for radio amateurs in the UK to have access to frequencies between 501-504 kHz or 508-515 KHz at a transmit level of 10W ERIP, in order to extend their experimental work, and thus understanding of low frequency propagation mechanisms, from work complementary to 73kHz, 136kHz and 1810kHz.  The two frequency bands options are proposed, as they are no longer used for maritime telegraphy in the Western hemisphere, their usage for non-directional aeronautical beacons (NDB) is being phased out.  It is understood that it is unlikely, in the near future, that the channels will be re-allocated to another service. 

Experimentation rationale

A frequency allocation around 500kHz will offer a number of unique opportunities and capabilities to the amateur service.  This will include ultra-reliable regional ground-wave communication, and secondly, further significant opportunity for extending the traditional merits of amateur radio – operating skill, self-learning and social interaction – and also the broad benefit to the national science and engineering skill and knowledge base.

UK spectrum regulation and its attitude to licensing amateur radio activity has for a number of years been innovative.  In response the UK amateur has shown respect for its privileges and made good use of opportunities to experiment with new frequency bands.  Examples are the temporary allocation at 73kHz[1] and currently the experimental access to channels at 5MHz. 

Whilst it is legendary the way in which radio amateurs, in the early years of the last century, were able to demonstrate the usefulness of the HF spectrum, it is still possible for amateurs to contribute to knowledge about radio propagation.  This is because amateurs often tend to study and then exploit anomalous propagation.  Examples of this, where recent findings on a long-term study the transatlantic path at 73 and 136kHz[2], and more recently, the unexpected long-path propagation between Rodrigues Island, in the Indian Ocean, and the West Coast of the USA on 1.8MHz.

The amateur experiments at 5MHz are aimed at the long-term collection[3] of data to understand and predict quality of service for inter-UK communication at that frequency.  Apart from collecting and aggregating station logs from participating amateur stations beacons are planned[4] that provide S/S+N and multipath/doppler assessment on either a manual or automatic basis.   Preliminary discussions have been started with Bath University for assistance in analysing the complex set of data in order that scientifically valid conclusions can be drawn from the work.

Rationale for 500kHz

Ground-wave  (also called surface-wave) propagation at low and medium frequencies can provide reliable communication over medium and large ranges.  The ground-wave signal propagates along the surface of the earth.  Such communication is omni-directional and continuous and is therefore well suited to nodal or network type of communication.  Since the ground-wave signal is not dependent upon the ionosphere, communications based upon ground waves are not interrupted by solar events (sunspots, solar storms, coronal mass ejection [CME]) or a high-altitude nuclear detonation that disturb the atmosphere.  A recent burst of solar activity (November 2003) produced significant aurora and disrupted HF ionospheric communication for days.

The optimum frequency for ground-wave communication depends upon the aerial efficiency, ground-wave propagation loss, atmospheric noise and of course man-made noise local to the receive station.  Given typical capabilities of radio amateurs, where aerials are far smaller than comparative commercial installations, the best S/S+N per watt of transmitter output occurs in the range 400 to 600kHz[5].    A frequency of 500kHz would therefore be ideal for low-information rate emergency communications, which was its rationale for being used for so many years as the maritime distress frequency.  An aim for the initial experiments would be to confirm that within a 1Hz receive bandwidth and 10W ERIP from the transmit aerial, the estimated ground-wave coverage of 300km can be realised for S/S+N of 20dB[6].

The radio amateur’s propensity for studying anomalous propagation is a part of the rationale for seeking access to 500kHz as it is situated part-way between the two existing amateur allocations at 136KHz and 1810kHz.  Skywave signals are a feature of both of these existing bands, more predominant at the latter, but never the less also after a CME event at 136kHz as a propagation enhancement.  Amateur access to 500kHz, would allow studies to be carried out to assess any anomalous skywave propagation.  This would be an important part of the study given some continued usage of the frequencies elsewhere in the World.

MF frequency Allocations in Region 1

The recent report under Ofcom contract AY4602[7] states that the band 415 – 526.5 kHz (primary and co-primary) is mainly allocated for MF telegraphy.  It details that the bands were stated at the Regional Administrative Conference for the Planning of the MF Maritime Mobile and Aeronautical Radionavigation Services (Region 1), Geneva, 1985:

The report goes on to say that the technology that is used on these frequencies ranges from Morse telegraphy to SSB, narrow-band direct-printing (e.g. NBDP and NAVTEX) and direct selective calling (DSC).  And comments that due to the international character of the usage of the channels, progress is slow to implementing the newer technologies; the expected move from Morse telegraphy to NBPD has not been realised and Morse telegraphy is virtually the only usage in Europe.  The only usage in the frequency range of interest are the NAVTEX transmissions from Niton, Cullercoats and Portpatrick on 490 and 518 kHz, augmented for UK waters by a site at Valentia and Malin Head in the Republic of Ireland.  Maritime safety information is all carried on channels outside the frequencies of interest (but some within the existing amateur band at 1810-2000kHz.

The UK closed down all its coastal stations several years ago, which included the monitoring of 500kHz, their roles in provision of public communications needs of ships have been met mainly by GSM or satellite services.  Thus, apart from the frequencies used for distress and safety (490 and 518 kHz) the frequencies in this area of the spectrum around the UK are unused.  WRC-2003 made no pertinent decisions on the re-use of these frequencies.  Furthermore, because of the possible EMC problems from un-intentional RF radiators, such as wire-line electronic communication, it has been suggested that the MF and LF parts of the spectrum are not reallocated until more efficient distribution systems for Internet broadband are developed.[8]  The report also concludes[9] that it would be “worthy of consideration” any approach for an amateur allocation in the vicinity of 500kHz.

Our study of the allocations in the region 435-525kHz suggest that 500-517 kHz would be the clearest area of spectrum for experimental amateur activity as it avoids the planned use of 435-495 kHz by the US Coast Guards for high-accuracy DGPS transmissions, maritime telegraphy in Region 2 and any residual Aeronautical NDBs at 505 kHz and above.  The emergency and distress frequency of 500kHz is only being monitored, as far as we can establish, by the Chinese and their regular use of the frequency is understood to finish in 2005.  Our own monitoring shows that the NDBs within 495-505 kHz appear to have been phased out and the sub-band appears clear.  We therefore propose access to 501 to 504 kHz for initial experiments – this would provide for “guard bands” approaching 1kHz for any residual or special event services at 500 kHz and a further 1kHz “guard band” for any residual NDBs at 505 kHz.  An alternative, depending upon the demise of the NDBs would be a 7kHz wide band from 508-515 kHz, i.e. the space between 505 kHz and 518kHz with a 3kHz “guard band” at each end.  This latter proposal would avoid any residual concern over 500kHz and give appropriate clearance for the NAVTEX transmissions on 518kHz.   The proposal would be for a 10W ERIP, based on the initial practice at 1810-2000 kHz amateur band and experience gained at 136kHz. 

Harmonisation

Amateur radio operation, bandplanning, EMC, etc, is coordinated globally through the International Amateur Radio Union (IARU).  This proposal has been drafted in full consultation with the IARU Region 1 500kHz Working Group, formed by the RSGB and chaired by the Belgium National Society, UBA, after WRC 2003.  The Working Group has representation from all 3 regions and thus gives visibility that similar requests for amateur experimental access to 500kHz is being sought by other countries, e.g. Australia, USA, and New Zealand.

Administrative aspects

The Radio Society of Great Britain, RSGB, has long-established experience at coordinating Notice of Variation (NoV) issuing and administering / policing activity on privilege access to spectrum.  For the proposed UK amateur access to 500kHz it would plan to follow the existing process, well tried and tested, which it uses for controlling 5MHz access.   This was developed from the earlier period of issuing NoVs for 73kHz.  To keep the number of NoV’s initially issued down to sensible numbers the first tranche of NoV applicants should, ideally, be able to demonstrate that they have successfully built and/or operated stations on 73 or 136kHz. Dependent upon demand a second tranche of NoV applicants could include Advanced Class Operators who demonstrate a genuine desire to further their skills through self-learning and experimentation. Another feature of the administrative process would be that it would provide a rapid “shut-down” service, should undesirable interference to the primary user be reported. 

20^th September 2004

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