E - Telephony, including sound broadcasting — Page 48, Lesson 49

Let’s start with the big idea. Every radio transmission is described by an official three-part designator — three characters that tell you exactly what kind of signal is being sent. The first character tells you the type of modulation, the second tells you what kind of information is in the signal, and the third tells you what that information actually is. Take J3E, which is the designator for HF radio telephony. The J means amplitude modulation, single sideband with suppressed carrier. The 3 means single channel containing analogue information. The E means telephony, including sound broadcasting. So when you put it together, J3E means an RF carrier wave is being amplitude modulated with speech, then the RF carrier wave is removed along with one of the sidebands. That’s the whole point of single sideband — you keep the intelligence, you throw away the carrier and one sideband to save power and bandwidth. Now, you don’t need to memorise the whole table of designators, but I want you to recognise the ones relevant to the equipment you’ll meet in phase 2. ADF is N0NA1A or N0NA2A. VHF RTF is A3E. HF RTF is J3E. VOR is A9W. ILS is A8W. Marker beacons are A2A. DME is P0N. MLS is N0XG1D. Let me decode a couple so you see the pattern. A3E — the A is amplitude modulation, the 3 is single channel analogue, the E is telephony. That’s your VHF radio. A9W — the 9 means a composite signal, and the W means a combination of two or more of the other categories — that’s VOR. A8W — the 8 means two or more channels carrying quantised or digital information — that’s ILS. A2A — the 2 means a single channel with quantised or digital information, and the A is telegraphy for aural reception — that’s your marker beacons. P0N — the P is unmodulated, the 0 means no modulating information, and the N is no audible information — that’s DME. One practical note: with the exception of ADF, it’s unlikely that knowledge of these designators will be examined. So don’t stress about memorising every letter — but do understand what J3E means, because that’s the one you’ll actually use on HF.