re "Problem is, just like other mode operators have found out, it's
unworkable as the majority of legal, in progress qso's will be derailed by
someone else firing up."
Its only unworkable because the implementation of the busy frequency
detector in question is obviously quite poor.
re "Since the CW op has no way to ask in ALE, PSK, whatever mode "is the
frequency in use", all they can do is interfere. so the mythical busy
detection software would have to have a way to answer back "sorry OM, the
frequency is in use" in every imaginable mode."
No, an automatic station already in QSO need only respond with "QRL" in CW,
which will be understood by the majority of attended stations.
re "Fact: Radio is vulnerable to "hidden terminal" effect like most shared
media. We live in that world. And because of that, there will be some
unintentional interference."
This is rarely problem with attended stations; you might not hear one side
of an in-progress QSO, but you will hear the other side, and be able to
respond appropriately when the side you hear asks you to QSY. Only automated
stations without busy frequency detectors suffer the vulnerability you
describe here.
Effective multi-mode busy frequency detection has been demonstrably feasible
for years. Had a concerted effort been made to equip all automatic stations
with competent busy frequency detectors, the rate of "QSO breakage" caused
by such stations would have plummeted, the anger caused by this QSO breakage
would have dissapated, and we'd be efficiently sharing spectrum in the
pursuit of our diverse objectives. Instead, we've been treated to years of
blatantly lame excuses as to why busy frequency detection either can't be
designed, can't be implemented, can't be deployed, won't work, causes warts,
causes cancer, causes global warming, or will cause the universe to expand
forever. Few are fooled by this.
73,
Dave, AA6YQ
-----Original Message-----
From: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com]on
Behalf Of Alan Barrow
Sent: Tuesday, November 24, 2009 8:14 PM
To: digitalradio@yahoogroups.com
Subject: Re: [digitalradio] Digital busy detect
Charles Brabham wrote:
>
>
> Packet radio gets by with a simple carrier detect, PACTOR can only
> detect other PACTOR stations, and from what I can tell, ALE has no
> busy detection at all.
Absolutely not the case. ALE listen's before transmit for other ALE by
protocol. And the commonly used ham implementation has a busy detection
mode that works for rtty, carrier, and most CW. Just does OK on voice,
but that's less of an issue as any operation in the voice sub-bands are
attended.
Problem is, just like other mode operators have found out, it's
unworkable as the majority of legal, in progress qso's will be derailed
by someone else firing up. Since the CW op has no way to ask in ALE,
PSK, whatever mode "is the frequency in use", all they can do is
interfere. so the mythical busy detection software would have to have a
way to answer back "sorry OM, the frequency is in use" in every
imaginable mode.
I see this in the PSK bands by CW & RTTY ops, and happens to pretty much
any digi mode. It's not unique to ALE for sure.
Fact: Radio is vulnerable to "hidden terminal" effect like most shared
media. We live in that world. And because of that, there will be some
unintentional interference.
Regarding busy detection, I've posted youtube video's of ALE's busy
detection in action. Packet's is not the most effective, by any means.
All that said, until there is mutual respect of the digi modes right to
exist, no one will widely use the busy detection as it's too easy to
hold off or interfere with a station running it. see it happen every day
on the busy ALE frequencies, and for sure this has soured winlink on
busy detection. It's not technology, it's your fellow hams.
When I see all psk ops wait for 2 complete transmission cycles to ensure
there is no hidden terminal effect, then ask "is the frequency in use"
before transmitting I'll concede. Same for RTTY. Until then, it's just
one mode complaining about the other, and we won't see progress.
Have fun,
Alan
km4ba
