RSM conserves spectrum that’s good for long distances by setting minimum path lengths. Engineers are not allowed to certify licenses that don’t meet the minimum length.
This table is a summary from Radio Licence Certification Rules (PIB 38) - Issue 12 (March 2021) p 47-48.
Bands | Frequencies | Minimum Length |
|---|---|---|
5 GHz | 4.4-5.0 GHz | 30 km |
6, 7, 8 GHz | 5.925-8.500 GHz | 20 km |
10,11,13,15 GHz | 10.5-15.35 GHz | 5 km |
18 GHz | 17.7-19.7 GHz | 2 km |
Exceptions (dispensations) can be granted by the RSM licensing team in special circumstances, but RSM has on obligation to do so. Examples where exceptions have been granted in the past:
The license was for one part of a longer path that involves a passive repeater
The license was in a remote area where there’s no possibility of spectrum exhaustion - and extended a system in the same frequency band.