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ups.com...

an_old_friend wrote:
wrote:

and why is it a problem I thought CW always got through, yet it needs
protecting from Pactor?

No, CW does *not* "always get through".

Assuming the robot listens before sending well it looks like anything
else I hear about in HF

No, robots do *not* listen before transmitting which is against the
regs and is the crux of the problem.

Brian,

Most of the "robots" *do* (at least make an attempt to) listen before
transmitting ... however the vagaries of propagation and the highly dynamic
nature of usage in the HF bands cause a serious "hidden terminal" problem
and that results in interference (it's unintentional, but still there - and
it happens more with "robots" because their "listen before talk" is not as
effective as a human sending "Is the frequency in use" and being
appropriately patient before blasting away).

A human operator causing QRM is either lousy operating practice or an
accident, a robot blindly causing QRM via it's inherent design is
illegal. One solution might be to come up with a robot which tunes
around it's frequency before transmitting. There's one for you
code-writers to chew on.

Solving the hidden terminal problem on HF for automated stations is a
difficult nut to crack ... in addition to the propagation issues and the
dynamics of usage, there are so many modes that a "robot" would have to
sense/detect/recognize to optimize the "clear channel assessment" and it
would have to do it quasi-continuously ... I'm not saying that it's a
permanently insoluble problem, but for now the mechanisms aren't up to the
level that's needed.

My working group, IEEE P802.22, (http://www.ieee802.org/22) is working on
"cognitive radio," but in response to the FCC's NPRM on license-exempt
devices using geographically unused TV channels ... this situation makes the
"incumbent detection/avoidance/protection" a more soluble problem because
there are a limited number of incumbents, they are high power transmitters
at generally fixed, stable locations, they use the same standards (NTSC,
which will be going away, and ATSC the new digital TV standard), the
spectral characteristics of their transmissions have "features" that are
easily detectable (the NTSC carriers or the DTV "pilot carrier"), etc.

However the "detect and avoid" problem becomes much more difficult in an
environment with many lower powered stations that come and go, whose
locations vary, and who use a wide variety of different modulation
techniques ... again, these problems will likely be solved in the future,
but we're not there yet.

73,
Carl - wk3c