Rising RF noise floor calls for urgent action
In 1999 the US Federal Communication Commission (FCC) requested that their Technological Advisory Council (TAC) study the noise floor and propose new approaches to spectrum management based on emerging and future technologies. Yet some 16 years later no such studies have been conducted.
For the past decade new noise sources have been developed, and will continue to develop. The proliferation of electronic devices and their unintended radio frequency interference outstrip regulatory initiatives and the ability for organisations such as the FCC, Ofcom and ICASA to take action against offenders. In June 2016 the TAC announced plans for a noise floor study and invited input to help answer questions about the study of changes to the spectrum noise floor over the past 20 years.
Recently, following a concern raised by the South African Radio League (SARL) at the SABS TC73 meeting, it was agreed that the question of the increasing level of the RF noise floor should be included in the strategic business plan of the technical committee and added to the work schedule of Working Group 6. Noise in this context denotes unwanted radio frequency (RF) energy from man-made sources. Like many spectrum users, radio amateurs have reported that the noise floor in the radio spectrum is rising as the number of devices that emit radio energy grows. However, in search for concrete evidence of increased noise floors, it appears that only limited quantitative data to support this presumption is available.
A typical noise intensity graph in different environments in Vienna, Austria as a result of a PLC network in the area.
Radio spectrum noise is generated by many different types of devices. Devices that are not designed to generate or emit RF energy but do so as a result of their operation are called incidental radiators. Most electric motors, light dimmers, switching power supplies, utility transformers and power lines are included in this category. There is little regulation governing the noise generated by these devices. Noise from such sources is expected to be minimised with “good engineering practices”.
Devices that are designed to generate RF energy for internal use, or send RF signals by conduction to associated equipment via connected wiring, but are not intended to emit RF energy, are called unintentional radiators. Computers and many portable electronic devices in use today, as well as many new high efficiency lights, are included in this category. Current regulations limit the levels of emitted RF energy from these devices but conformance is difficult to monitor or enforce.
Unlicensed intentional radiators, industrial, scientific, and medical radiators, and licensed radiators are devices that are designed to generate and emit RF energy by radiation or induction. Such emitters contribute to the noise floor with emissions outside of their assigned frequencies. These are sometimes generated as spurious emissions including, but not limited to, harmonics of desired frequencies and intermodulation products. Regulations that permit the operation of these devices also specify the limits of emissions outside of licensed or allowed (in the case of unlicensed devices) frequencies of operation.
The SARL is joining a number of members of the International Amateur Radio Union (IARU) to highlight the problem which will ultimately affect all users of the radio frequency spectrum. The internet of things has the potential of increasing the RF noise floor which would adversely affect small signal sensors. This should in itself make industry more aware of minimising the impact on the RF noise floor by exploring innovative designs and complying with strict specifications. IARU members such as the American Radio League, the Radio Society of Great Britain, and the Netherlands VERON are supporting the call. The ITU has an ongoing study until 2019. The IARU Region 1 EMC committee chairman, Thilo Kootz, has developed and released software called “noise reporter” which is a basic tool to monitor man-made noise at the location of a radio amateur and compare it with data from the ITU. No special equipment is needed, just the amateur’s own radio equipment. Kootz said that the benefit is that data can be collected by thousands of radio amateurs and analysed to develop a global picture. The SARL will be holding a RF Noise Floor workshop at the National Amateur Radio centre on 8 April 2017 to develop a coordinated programme.
Interested parties to contact hans.vandegroenendaal@ee.co.za
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