This report is that document, as authored by Dr Nash, in all its original detail. Starting with the existing version of the CIMO Guide (2010 update) Dr Nash revised that information, primarily to include the additional understanding gained from the Yangjiang intercomparison. At the same time, though, he added a wealth of further specialist knowledge, gained from his protracted involvement in WMO CIMO activities over more than thirty years, and in particular from his participation in all eight CIMO international radiosonde intercomparisons, commencing with the first, held at Bracknell in 1983. This report comprises a treasure trove of information on radiosondes and other upper air measurement technologies and techniques. It contains the distilled knowledge and understanding gained by Dr Nash over the thirty years of his experience in testing and operating radiosondes. It is essential reading for anyone with a specialized interest in radiosondes.