DANNY DOUGLAS thoughtfully asks: > We already require this of CW/SSB/RTTY/PSK etc. users. Why should a > user of these higher-newer modes not be held to the same requirements? How is busy channel detection done in PSK or RTTY? people listen for a bit then, transmit. It's not common practice, nor is there an easy way to ask "is the frequency in use" like in voice. CW ops sometimes ask, but not as common.
So all digi'ish modes typically fail the hidden terminal detection, which is the majority of QRM. With PSK transmissions taking as long as they do, very few ops listen on a frequency long enough to determine that there is no qso in process. I've commented previously, all HFLINK related ALE operation is confined to band segments where automated operation is allowed. And yes, that means there is risk of hidden terminal interference like with all radio. All other ALE operation is in attended mode, no soundings, and only semi-auto response when queried by another station. At my ALE station, clicking the mic PTT terminates the digi transmission. So in attended mode I can kill or hold off any semi-auto response. I do whenever needed. 99% of the time it's someone interfering with my qso in progress, but I still hold it off. Since the HFLink promoted practice is to operate attended mode only outside of the auto sub-bands, you will find very few cases of interference in other band segments. If it does happen it's unintentional due to hidden terminal effect. No soundings, just hams calling & kbd chat just like rtty/psk. Or using selcall (also allowed) in the voice bands. So yes, HFLink has promoted ALE operation. But it's also channeled that operation into areas to minimize unintentional interference to the limits of technology. And by defining "net" frequencies, have managed to focus even unattended operation away from frequencies used by incompatible uses. (QRP, PSK, SSTV, etc) The significant majority (up in the 95-99%) of ALE activity is on one 3khz frequency per band. Yep, a full 3khz, widely published. And contending with packet bbs's, winlink pactor, and many other modes. You might find some kbd qso's on ALE on another defined freq per band. And the normal HFPack voice net frequencies may see occasional (very rare) ALE selcall's, but no other ALE activity. Likewise, we've tuned and tried to standardize the various ALE settings to make it "ham friendly". This is everything from call duration, to the various arcane ALE settings. Your question is a valid one, and we've tried very hard to practice "good neighbor" policies. I like to think we do better than many user groups. I find it hard to reconcile the bedlam your average RTTY contest weekend with complaints about ALE operation. But we feel an obligation to practice good neighbor operation, and wish others would do the same. Have fun, Alan km4ba
