> Skip KH6TY wrote: > > Look at it this way - NO transmissions without listening first, > either ALE soundings, beacons, or mailboxes of any kind, > are permissible on the *shared* HF amateur bands, except > in designated beacon areas or the automatic subbands > ( where it is presumed by the FCC to occur, since unattended > stations do not, and cannot, listen first for any other activity > within range of the unattended station).
Hi Skip, The ALE-141 standard includes "listen-before-transmit" for ALL transmissions and the ALE modem controllers have channel occupancy detectors that can detect other signals than ALE. ALE listens before transmitting and listens after transmitting. This standard is the main one used by hams, and we have adapted it with some improvements to further enhance it for non-interference... Ham-friendly ALE operation details that any scheduled station IDs happen only in the automatic subbands. Currently, 90% of selective calls, and nearly 100% of all text messaging happens in the automatic sub-bands. All HF frequencies are shared these days... whether they are amateur radio bands, commercial, or government channels. No one has "exclusive" channels any more, with few exceptions. Over half of the non-amateur 2-way communications transmissions on HF now are ALE signals, or begin with an ALE exchange of some type... ALE is quite simply, the main method being used now for initiating and maintaining communications on HF. There are many reasons for so many services adopting ALE, the primary one is that ALE works well... and it enables many stations or entities to share HF frequencies easily. Oddly the original premise that ALE was only for unskilled operators turned out differently than they expected. In the hands of skilled operators, ALE is being used like a force multiplier to enable skilled radio operators to handle more traffic and to monitor and communicate with more nets simultaneously. Hams are late to the ALE party, but we are bringing a few interesting innovations of our own with us :) 73 Bonnie KQ6XA
