BACKGROUND There has recently been a lot of bloated theoretical talk about Automatic Busy Detection. My observation is that most of the operators who glorify it and exalt its virtues, have nearly zero experience using it on the air! The same guys who have no experience with it, want to make auto busy detection mandatory for everyone else! Let's get down to the reality of automatic busy channel detection. AUTO BUSY DETECTION - THE REALITY I can tell you from real experience using it on a daily basis in the ham bands, that automatic busy detection should never be mandatory!
The reality is, automatic busy detection is a two-edged sword: Automatic busy detection has big advantages. Automatic busy detection has big drawbacks. WHO IS CURRENTLY USING AUTO BUSY DETECTION? There are some of us who have been using automatic busy detection with ALE for a number of years on the ham bands. In fact, I believe the ham radio ALE network is one of very few nets that currently use automatic busy detection on a regular basis. Does anyone else know of another HF system using auto busy detect? ADVANTAGES It helps prevent interfering transmissions when a channel is busy. In some cases, the busy detector is more reliable than a human operator. Certainly, even the simplest auto busy detectors are much more courteous and polite than most "contest operators" or "avid DX chasers". The auto busy detector can greatly help to enable automatically controlled stations to interact and cooperate reliably with manual stations. I've found that it is generally convenient to use automatic busy detection for normal operation when the radio is scanning or listening on a channel for stations to connect. It also provides a polite way to automatically postpone station ID transmissions until an ongoing QSO on a channel is completed. As an example, my busy detector is programmed to return to a channel and try again 6 minutes later. DISADVANTAGES Noise can cause false busy channel indication. This prevents use of an otherwise clear channel. Reliable positive and reliable negative discrimination for all signal and noise cases may not be dependable or practical in the ham band environment where any type of signal working at any QSO level of SNR may be transmitted on any frequency. Some of these signals may appear as noise or as too weak to be reliably detected by the human ear, by human eye viewing a waterfall. One clear example is Olivia MFSK with QSOs operating at -15dB SNR. Most humans cannot perceive these extreme weak signal QSOs and the busy detector may not either. ADJACENT CHANNEL INTERFERENCE Minor adjacent channel interference to a busy-detector-enabled station has the potential to totally prevent or stop communications. This is especially important for emergency traffic, and is also important for reliability on a daily basis. ABUSE OF SYSTEM BY INTENTIONAL INTERFERENCE If automatic busy detection was to be mandatory or obligatory, all stations using it would become very tempting targets for nefarious intentionally interfering operators to abuse the system. Operators using automatic busy detection would be open to potential abuse when it becomes known that any intentional QRM will halt their transmissions. SUSCEPTABILITY TO INTENTIONAL AMBUSH There is great potential for a nefarious operator to lie in wait on a clear channel, and ambush all others who attempt start a QSO. It would be possible for any nefarious operator to anonymously stop a bonafide QSO already in progress, simply by QRMing the automatic busy detector. REMEDY TO INTENTIONAL INTERFERENCE I have personally experienced intentional interference, and fortunately, I was aware of the situation and simply disabled the auto busy detector. CONCLUSION In my experience over the past several years, automatic busy detection seems to work best when no one knows you have it enabled! This goes hand-in-hand as an option that can be easily turned on/off at will by the operator. Bonnie Crystal KQ6XA .
