[RTTY] Fw: ALE Sounding. What is it and how does it work?

[Joe Subich, W4TV]

This entire issue simply shows that any protocol which includes 
automatic transmission (beaconing, sounding, etc.) or which can 
autonomously reply to remote interrogation should be required to 
contain and implement a "channel busy" detection circuit that 
will inhibit transmission if there is any activity within a 
window 1.5 times the "necessary bandwidth" for the modulation 
in us.  Thus if one were to operate a RTTY responder using 170 Hz 
shift 45.45 baud RTTY, the software should be required to inhibit 
automatic or autonomous transmission if there was any signal (CW, 
PSK31, RTTY, MFSK, etc.) in a 400 Hz Window (using 260 Hz as an 
estimate for the "necessary bandwidth").  If one were using PACTOR 
III that could "up shift" to a mode that required 2.5 KHz, the 
protocol/software should require a "clear" 4 KHz Window.  

The protocol should also be required to detect all coherent (non-
noise) modulation methods and not simply its "own kind" to prevent 
interference between incompatible methods of modulation.  Given 
advancements in digital signal processing, such a requirement is 
not excessive, nor particularly "costly" in terms of development 
resources. 

None of the automatic or semi-automatic systems currently in use 
have any kind of listen before transmit safeguards for "incompatible" 
modulation methods or protocols.  With the compression of spectrum 
in which digital (non-voice) operation is permitted to US amateurs, 
increased protection from the "robots" is vital. While "semi-automatic" 
operations have been a problem to human operators since they were 
first popularizes in the mid-1980's, fully automatic systems have 
not been a significant issue due to the relatively separate spectrum 
for "automatic operation."  Rapidly increasing levels of narrow 
band digital activity due to interest by new HF operators and the 
relatively easy access to software like MixW, WinWarbler, MMTTY, 
MMVARI. MultiPSK, FLDIGI, etc. coupled with the significant reduction 
in non-voice spectrum will make the conflict between human operators 
and automatic or autonomous operations critical in the very near 
future.  

The only way to prevent conflict is to require that automatic and 
autonomous systems observe the same "listen before transmit" behavior 
expected of human operators and embodied in the rules of the Amateur 
Service that states "no licensee 'owns' any frequency." 

73, 

   ... Joe, W4TV