re "So you add a magic "frequency is occupied" device to your digi mode. You are legitimately on a frequency, in a digi qso. Yet someone who does not the remote station (hidden) fires up, and stays fired up. At that point, your anti-qrm tripped, and you just lost the frequency, and your qso is terminated. "
This would only be true of an extremely naive implementation of a busy frequency detector. The purpose of a busy frequency detector is to prevent an unattended station from initiating a QSO (or responding to a request to initiate a QSO) on a frequency that is already busy. If the unattended station is already in QSO, detection of a signal other than that of its QSO partner would not terminate the QSO. re "Lot's of the (perceived) issue is the classic "hidden terminal" nature of radio.... you may think a frequency is clear because you hear nothing, but in fact, it's a qso in progress where you can only hear one end. You fire up, and turns out you just stomped on someone. Happens on voice, cw, psk, RTTY, it's equal opportunity." Yes, this does happen, but you neglected to describe the rest of the scenario. The "end" that you can hear says "QRL, pse QSY", and most operators quickly oblige. In contrast, unattended automatic stations *cannot* oblige; they blithely QRM away. An unattended station with a proper busy frequency detector would have likely been monitoring the frequency long enough to detect the copiable half of the QSO already in progress, and thus would never have transmitted on the first place. re "Happens all the time. Some versions of ALE software have reasonable busy freq detectors. Winkink has deployed & tested busy detection. Yet in real life it's unusable, as it pretty much derails any legit qso in progress when other folks (cw, rtty, pactor, whatever) fire up. The naive busy frequency detector, again. re "And when it's been deployed in the winlink world, there has clearly been intentional QRM to hold off the digi's" Yes, Winlink has generated an enormous amount of ill will, to the point where some ops have become so angry that they will waste their time QRMing an automatic station. There is no excuse for this illegal behavior, but its *ludicrous* to use this as an excuse to avoid eliminating the problem by deploying busy frequency detectors. Once Winlink and other unattended automatic stations reduce their QRM rate to something approaching that of the average human operator, the anger will dissipate and the QRMing of automatic stations will dissappear. 73, Dave, AA6YQ -----Original Message----- From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com]on Behalf Of Alan Barrow Sent: Tuesday, November 24, 2009 7:14 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Disinformation about ALE by N5PVL Re: Getting serious about ALE / LID factor KH6TY wrote: > Your prejudice is obviously showing! (Uh - long live HFlink and others > that run unattended transmitters outside the beacon bands and transmit > without checking for a clear frequency???) > With tongue in cheek: "your ignorance is showing" (in the misinformed sense, no insult implied) All unattended ALE operation associated with HFLINK operates solely in the band segments set aside by the FCC for "automatic" operation, including unattended. It's a very narrow slice in each band, and quite full of packet BBS, winlink, and ALE. Given the huge (comparatively) segments where narrow modes (rtty, psk, etc) are allowed that are free from competition, I don't see just cause for complaint. You may not like it, but it's an allowed operation mode in an allowed band segment. ALE activity in other portions of the band is attended mode, with the same guidelines/recommendations for listen before transmit. > The point Charles is making is that transmitting without listening is > simply exceptionally inconsiderate on shared frequencies by all widely > accepted standards of behavior, but you obviously do not get it, and I > guess you really don't want to, do you... Simply put, "frequency > sharing" means not using a frequency unless you have made a reasonable > attempt to verify it is not being used. There is no technology yet > implemented that makes this possible for an unattended station. So help me out, how does the repeated rtty transmissions in contest weekends handle this? I see 100x the examples of xmit without listening during rtty contests then all the semi-auto modes put together? Lot's of the (perceived) issue is the classic "hidden terminal" nature of radio.... you may think a frequency is clear because you hear nothing, but in fact, it's a qso in progress where you can only hear one end. You fire up, and turns out you just stomped on someone. Happens on voice, cw, psk, RTTY, it's equal opportunity. BTW, no one asks in psk "is the frequency in use?". So you add a magic "frequency is occupied" device to your digi mode. You are legitimately on a frequency, in a digi qso. Yet someone who does not the remote station (hidden) fires up, and stays fired up. At that point, your anti-qrm tripped, and you just lost the frequency, and your qso is terminated. They are in a different mode, and did not ask is the frequency is in use. You would not have decoded it if they did. Happens all the time. Some versions of ALE software have reasonable busy freq detectors. Winkink has deployed & tested busy detection. Yet in real life it's unusable, as it pretty much derails any legit qso in progress when other folks (cw, rtty, pactor, whatever) fire up. And when it's been deployed in the winlink world, there has clearly been intentional QRM to hold off the digi's. I see it even now on the ALE net freq's in the auto sub-band: lot's of space in the cw bands, even for no-code/novice. Yet a cw station will fire up in the center of the ALE, packet, and winlink all sharing a few khz for unattended operation. My view, it's tantamount intentional QRM, as there is a 100% chance of a digi station being queried by a hidden terminal. I've even heard them joke about it in the CW qso. It would be a wonderful world if there was a workable solution. I've tried in the past, and would try again, any workable approach. But what I find is that the anti-digital hams (including some rtty) will absolutely take advantage of any good faith attempts to derail legal activity they don't like. Personally, I don't think this will ever be resolved until each band is sliced by bandwidth & nature of operation (wide/narrow, analog/digi, attended/auto). We'd all lose, but since no one will compromise, there's not an alternative. Have fun, Alan km4ba