Any HF radio equipped aircraft will have to carry out a full radio check after maintenance. We carried out weekly checks on all our radio gear including HF comms x2 and a Selcal test. If there was an avionics guy up front then it all went well but often the checks were done by the airframe/engines engineers. They weren't as savvy on the HF use and often didn't check that they could hear (or not!) the station they were calling - being used to the quiet background of VHF comms - so they would call the ground station not knowing they were interfering. Then they get on the radio to the avionics workshop complaining that the HF doesn't work....so we had to go out to the aircraft and apologise to the HF station....Pilots have to do a pre-flight check too with a Selcal check and as they are on the ground, often cannot hear the other airborne stations - HF propagation for you! BTW if you listen frequently to the Aero HF it's surprising how many pilots don't get the first Selcal check and have to get a repeat "No Selcal, code bravo golf charlie hotel" then they remember to press the reset button....
