> Andy K3UK wrote: > As Bonnie mentioned last week, ALE has no busy detect for > none ALE signals. So yes, Soundings and certain other > aspects of ALE cause QRM.
Hi Andy, A few weeks ago, during the discussion about busy detectors, I described some of the different busy detect systems that are currently in use by various comm systems. Ham radio ALE operators are some of the few on HF who are actually using busy detection on a regular daily basis. These are in use with ALE for manual, semi-automatic, and automatic operation. There are two levels of busy detect normally in use with ALE. Both of these are available in PCALE and ALE hardware radios: 1. The first, basic busy detection level for ALE, recognizes ALE signals and other digi or CW signals that are mostly sine waves within the active signal occupancy range of audio frequencies. This type of busy detect is always enabled on ALE systems, and cannot be turned off by the operator. It also is used to recognize signals and frequently causes the ALE controller to pause while scanning. It prevents sounding or calls on top of other signals. If a sounding or scanning call transmission is prevented by this detector, the ALE controller comes back to the channel and tries again a few minutes later. The purpose of this is to prevent signal collisions of any type, and the listen time constant is short. 2. The second type of ALE busy detection is commonly known as "channel occupancy check", "polite mode", or "voice detect" and it detects signals that are voice-like within, above, and below the active signal occupancy range of audio frequencies. It is normally selectable on/off by the operator, and the listen time constant is long. It is good to enable it whenever a scanning call is being made. If a sounding or scanning call transmission is prevented by this detector, the ALE controller comes back to the channel and tries again a few minutes later. It is mostly used for ALE operation on the voice channels, but it has some benefit for normal non-critical or non-emergency application on the data channels also. As implemented in many ALE systems this super-polite detector tends to falsely prevent ALE transmissions very often. It can often be a royal pain in the rear end because of the close spacing between signals found on the ham bands. 73 Bonnie KQ6XA .
