During the period 20 – 26 October 2021, the IARU continued to engage in the preparatory work for WRC-23 agenda item 9.1b in ITU‑R Working Party 4C (WP4C).

The working party is considering simulations provided by two administrations to estimate the interfered area that might exist around a 23cm band amateur service transmitter. A number of amateur station configurations are under consideration identified as “Home Station 1”, “Home Station 2” and “Permanent Station” (e.g. Repeater station) based on characteristics developed and contributed by the IARU. Both narrowband and wideband emissions are considered. Two further scenarios are included in which “Home Station 1” operates with antenna uptilt as an amateur satellite uplink station and in which “Home Station 2” operates with antenna uptilt as an E‑M-E station.

A typical output plot from the simulations looks like this:

The colours represent the varying RNSS received level from high (red) to low (blue) around the transmitter in the centre. The red outline represents a RNSS receiver protection threshold (in this case ‑134.5 dBm)

The IARU representatives contributed to an off-line email discussion to ensure the amateur station parameters used are more representative than those that had been proposed in the original contribution papers. The studies were revised based on these negotiations during the meeting and are reflected in the draft working document. The interim results show interference distances of up to several km depending on the antenna and power level assumed. Work on these studies will continue into the next meeting.

Other measurements campaigns are investigating the effect of offsetting the transmission frequency of various amateur signals with respect to the centre frequency of the RNSS signal and the impact of the RNSS receiver bandwidth.

The IARU is working to ensure the amateur services are realistically represented in the studies as they move forward and remain consistent with the information developed in WP5A. It remains vital that national amateur communities present their views on the importance of this band to their national regulators in a consolidated and consistent manner.

The work on this topic will continue throughout the year both in ITU‑R and in the regional telecommunications organisations and the IARU is committed to ensure every group hears the amateur position on this important microwave band.

The summary report from the WP4C meeting can be found here .

The parallel work in CEPT SE40 is tracking the activity in the ITU‑R and is at a similar stage of development. This is also within the purview of the R1 SRLC.