• A national Air Force operates generally in a closed common user group. However, deviation to this regulation existed on German territory until 1990. E.g. the HQ-user of the
German Air Force in the North of Germany, operational subordinated to
2nd Allied Tactical Air Force used
HQ net-group 1, whereas the southern units, subordinated to
4th Allied Tactical Air Force, used
HQ net-group 2. • The co-ordination of HQ radio frequency channels in the
NATO-harmonised UHF-band, the design of the so-called
HQ hop-sets, is provided in NATO-Europe in responsibility of the
NATO Allied Radio Frequency Agency (ARFA) in Brussels. • For training and exercises, HQ operates in
peacetime mode with limited frequency access. Four net-numbers may be used overlapping in net-group 1 and 2. However, in
tactical operation mode this limitation might be lifted. • Some HQ-features are compatible to encryption hardware; e.g. to the
KY-58 VINSON-family. == Utilization in the US and NATO ==