The IARU Region 1 Spectrum Regulation and Liaison Committee (SRLC) chair took part in a joint session with the R1 Political Relations Committee (PRC) during the member society International Meeting convened during the HamRadio2022 Friedrichshafen event. The session highlighted the connections the SRLC maintains with Region 1 regulatory bodies and the work carried out since early 2021. This included engagement in the WRC23 preparatory activities in a number of regional bodies and the detailed study work both with ITU‑R and CEPT. The hot topics affecting amateur spectrum bands were summarised with particular attention being paid to the 23cm band topic on the agenda of WRC23.

The SRLC slide set can be found here.

Further detailed information on the 23cm band topic can be found here.

The latest meeting of ITU‑R WP5A concluded on June 2, 2022. The IARU was represented by Ole Garpstad (LA2RR – ITU Lead) and Barry Lewis (G4SJH – WRC23AI9.1b Lead).

ITU‑R WP5A is the study group at ITU which deals in part with topics related to the amateur and amateur satellite services. It is the lead group responsible for developing the Conference Preparatory Meeting (CPM) report on agenda item 9.1(b) This Agenda Item provides for a “Review of the amateur service and the amateur-satellite service allocations in the frequency band 1 240‑1 300 MHz to determine if additional measures are required to ensure protection of the radionavigation-satellite (space-to-Earth) service operating in the same band in accordance with Resolution 774 (WRC‑19);” The CPM Report will form the basis for consideration of this issue at WRC-23 next year.

At the conclusion of the recent WP5A meeting a draft recommendation was prepared which will provide guidelines to administrations to ensure the protection of the RNSS primary allocation from the secondary amateur and amateur satellite services.

The draft recommendation will be the most important element of the WP5A work going forward for the amateur and amateur satellite services in the 23cm band. The working document contains a number of proposals for severe limitations on amateur usage of the band including transmitter power constraints. Very low power levels are proposed for large portions of the band (100% in one case). Proposals also identify possible frequency band usage limitations for broadband applications (e.g. ATV), narrowband applications and amateur satellite services in 1 260 – 1 270 MHz.

A full report of the WP5A meeting can be found here.

None of these proposals are adopted at this time and work will continue at the next meeting of WP5A to rationalise the variations proposed by national telecom-administrations. The IARU will work to minimise the constraints on amateur radio activities and continue to seek amendments to the draft recommendations through the ITU process, but as a secondary user, radio amateurs should understand the need to protect the Radionavigation Satellite Service (RNSS) in many consumer and industry applications (like autonomous vehicles) that will lead to some restrictions on our use of the 23 cm band.

A detailed slide set relating to this topic can be found here.

During the period 4 – 10 May 2022, the IARU continued to engage in the preparatory work for WRC-23 agenda item 9.1b in ITU‑R Working Party 4C (WP4C).

Work continued to develop the coexistence studies between the amateur services in the 23cm band and the radio-navigation satellite services (RNSS) operating across the band. New studies were submitted by France, China and the Russian Federation.

The scale of the problem for the amateur services is becoming clear. For example, the studies predict that even a relatively low power 23cm band station could cause interference to distant RNSS receivers on the antenna main beam heading. Although the level of amateur activity and the density of users is quite low (compared to other more popular bands) the issue remains that from a regulatory perspective the amateur services are required to not cause harmful interference to RNSS services.

The figure below is a sample of one result from one study submitted into ITU‑R. In this example a station using an 18dBi gain antenna is used for both narrow band transmissions 100W. The protection criteria for the RNSS receivers differs for narrowband and wideband interfering signals. The figure shows the distances out from the amateur station where the RNSS protection criteria could be exceeded around the amateur station antenna .

These results have been developed based the ITU‑R defined receiver protection level for the GALILEO RNSS. For the narrow band modes this is ‑134.5dBW and for the wideband modes is ‑140dBW/MHz. In addition, measurement campaigns have shown that an improvement in the compatibility potential can be seen if the amateur signals avoid the centre portion of the GALILEO receiver passband.

Of course the studies cannot take into account every possibility that might mitigate the problem (e.g clutter, terrain blocking etc.) but it is clear that the potential for interference is considerable. 

The IARU is working hard to ensure that the amateur service can continue to develop in this band and allow all the amateur applications in use today to continue. However, given the heavy spectrum occupancy of the band by the various RNSS systems it is evident that proposals will come calling to restrict our ability to operate in certain parts of the band and at the power levels possible today. IARU is totally engaged in the discussion of these considerations and these will continue within ITU‑R (and other regional bodies).

The IARU summary report on the WP4C meeting can be found here which in turn includes a link to the full draft study.

The 4^th meeting of the CEPT project team (CPG PTC) tasked with developing the CEPT Brief for WRC23 agenda item 9.1b on 23cm band amateur service and RNSS coexistence took place during March 2022. The IARU R1 was present and provided a contribution to the working document. A summary report describing the contributions and the meeting activity can be found here.

The meeting did not tackle any technical studies directly but the developing brief reports and summarises the activities taking place in other groups where they are being carried out. Updates were made to the background including a description of the work carried out by the amateur community in CEPT and ITU‑R with respect to resolves 1 of the WRC-19 Resolution 774. Further updates were introduced to describe the study work taking place in ITU‑R (WP’s 4C and 5A).

The draft CEPT Brief will undergo further development as technical studies evolve in the wider regulatory community including both CEPT and ITU‑R. The next activity concerning this topic will take place in the CEPT arena (SE40) to progress the technical studies and the draft ECC Report.

As we head into 2022 the ITU‑R and CEPT work considering the 23cm band and coexistence with the RNSS systems (GALILEO, COMPASS, GLONASS, GPS…) will continue so where have we got to and where is it heading?

The IARU has provided extensive information regarding the amateur and amateur satellite service applications in the band 1240 – 1300MHz as well as operational characteristics and data indicating the density of active transmitting stations and the busiest periods when these are most likely to be operational. Using this data, one CEPT administration has provided an extensive set of propagation model predictions for a number of amateur operating scenario assumptions (including satellite working and EME operation) that predict an “interfered area” over which an amateur transmissions may be received by a RNSS receiver at levels exceeding a defined protection level. Another ITU‑R member administration contributed a smaller set of predictions using the same model. The received RNSS interference level that the RNSS can tolerate (receiver protection level) is based on ITU‑R recommended criteria and depends on whether narrowband or wideband interfering signals are being transmitted.

The propagation model predicts that an interfered area can extend out to several tens of km (depending on the scenario) but at the extremes of the area, the time probability of exceeding the protection level is very low (1%) and for only 50% of locations. The model can only assume a full power continuous transmission.

In addition much attention has been paid to documenting an interference case recorded in Italy between an Italian 23cm band repeater and GALILEO receivers at the nearby European Commission Joint Research Centre in Ispra where work is undertaken to develop and test GALILEO system applications. The impact of traffic through this very local repeater (12.5km distant) on three different GALILEO receivers has been documented. This work suggests that whilst RNSS receiver bandwidth can have a part to play in enabling coexistence, beyond that nothing has been reported that could help develop any coexistence criteria. Nothing is reported about the mode of failure in the receivers beyond degradation on C/N.

This one case is often cited as the “proof” that interference can occur.

At present the conclusions from this work are being developed (in ITU‑R and CEPT) and IARU work continues to ensure these results are put into a real world context to understand what they imply with respect to successful coexistence.

Amateur transmissions virtually anywhere in the band will be co-frequency with the RNSS receivers from one system or another. It is therefore obvious that any RNSS receiver will be open to any co-frequency amateur transmission and amateur operators have no way of knowing where or when a RNSS service user is active. Therefore IARU has expressed a view that for successful coexistence guidance to be developed, some compromises will need be necessary.

As we move through the work in 2022 we need these compromises will become apparent so that the amateur community can know how to respond appropriately in a way that can allow our diverse set of applications to continue to develop whilst minimising any potential disruption to RNSS services. It is anticipated that the international views on the ITU‑R studies will need to stabilise by the middle of this this year in order to meet the timetable for the WRC-23 preparatory work. These views will likely propose technical and operational measures to be applied to the amateur and amateur satellite services that could be formalised in the Radio Regulations.

As the study activities work towards conclusions it is vital that the national societies engage with their national amateur radio regulators to ensure they understand and hear about the importance of this band for the amateur radio community.