It is not necessary to decode in order to sense a busy frequency; it
is only necessary to detect any of the underlying forms of
modulation in use. There are far fewer modulation schemes than
modes. The SCAMP prototype demonstrated the effectivenss of this
approach.
Requiring a common header (both protocol and modulation format)
would certainly be more accurate, but "boil the ocean" approaches
are impractical in the amateur community.
73,
Dave, AA6YQ
--- In [email protected], DuBose Walt Civ AETC CONS/LGCA
<[EMAIL PROTECTED]> wrote:
>
> IMHO, there are only two ways of preventing HF data mode QRM other
than the
> "hidden tranmitter"...
> One is to have a universal mode decoder that would identify the
mode or
> require that each mode send a common protocol at the beginning of
each
> transmission to identify the mode and to have established sub-bands
> automatic/semi-automatic operation.
>
> The second is to break up a large sub-band into channels and have
each mode
> assigned a number of channels (all who want this raise their hand).
>
> I suppose the their way would be would be to only allow "accepted"
modes in
> one sub-band and agree to negotiate and QRM and all other modes in
another
> sub-band where you must accept any and all QRM.
>
> There maybe other ways, but its the way I see things now.
>
> Walt/K5YFW
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[EMAIL PROTECTED] Behalf Of Tim Gorman
> Sent: Tuesday, February 21, 2006 4:51 PM
> To: [email protected]
> Subject: Re: [digitalradio] Re: NTS and traffic handling and
digital
>
>
> Rick,
>
> I think the problem is more complex than this. I believe you will
find that
> sub-bands will ALWAYS be the answer of choice.
>
> First, I use a pk-232mbx on pactor in the automatic sub-bands as
part of the
>
> NTS-D system. This box only listens for other pactor stations. If
I were to
> be told that this was going to be banned from the ham bands, I
would drop
> out
> of the NTS-D. So would others who use exactly the same equipment.
None of us
>
> would have $1000 or more to get equipped with SCS modems. It would
be much
> better to keep these operations in the sub-bands and keep them
operating
> than
> to just kill the system by default.
>
> Second, I would be interested in how SCAMP operated when QRM came
on the
> frequency? Did it end the session so it wouldn't QRM the other
guy? Or was
> the busy detector disabled after the session had been established?
>
> If the later, the busy detection scheme is only a placebo for
many, many
> situations and not a true fix. Since the systems today offer no
true trunk
> system control signals (i.e. calls to a busy channel are not
abandoned by
> the
> originating end but just continue to be attempted) as soon as the
automatic
> station detects a clear channel (the station it could hear turns
the
> transmission over to a station that can't be heard) the session
will be
> started and will cause QRM. Bottom line? No difference. The QRM is
just
> delayed by one transmission period.
>
> The only situations which would be truly helped would be those
where the
> automatic station can hear ALL stations in the QSO on the
frequency of use.
>
> If SCAMP stops operation upon busy detection, even after a session
is
> established, it is likely that the system would come to a
screeching halt
> during busy times of the day. Since it is likely this is when long
distance
> propagation may be at its best, system throughput could be
drastically
> impacted.
>
> It would appear that the *only* way to minimize impacts of the
automatic
> stations is to maintain automatic subbands. Other operations who
want to
> venture into these areas should understand that protections
against QRM are
> not what they are in other areas.
>
> For those who think that restricting automatic operations to small
subbands
> is
> not fair to operations like Winlink, I would be happy to lay out
changes in
> operation that would let Winlink pass all of its traffic on five
500hz
> channels. That's not five channels per band but five total, and
Pactor II at
>
> that.
>
> To those discussing email content. It is my opinion, for whatever
that is
> worth, that it is *not* the content of a specific communication
that is the
> problem, per se, but the *regularity* of third party
communications. Regular
>
> communications with third parties are specifically mentioned in
the Part 97
> rules. It would seem to be axiomatic that for one time use or even
> non-regular use, almost any content could be allowed, even it is
not what
> most would consider acceptable. When the use is for third-party
> communications on a regular basis, especially the *same* third
party all the
>
> time, the use enters a different realm.
>
> For instance, I keep getting the issue of weather reports thrown
out when
> the
> subject comes up. These are *important* to ships at sea.
>
> Well, what would happen if I started broadcasting the local NWS
system on
> 3920khz or 146.52Mhz during times of bad weather? Wouldn't those
weather
> reports be important to people on the road during periods of snow
and
> freezing weather? If I were to do this on a regular basis, e.g.
24/7, does
> anyone on here think it would take more than a few days for me to
get a
> letter from Riley?
>
> Would the Winlink people support having this type of operation on
the ham
> bands?
>
> Just as there are other radio services providing this service
(i.e. the
> NWS),
> there are other radio services providing for regular, third party
email from
>
> ships, yachts, and boats, be they on land or sea.
>
> tim ab0wr
>
>
> On Monday 20 February 2006 22:14, KV9U wrote:
> > John,
> >
> > At one time it was not technically possible for a robot station
on semi
> > (or for that matter on fully) automatic, to be able to detect
diverse
> > signals in the pass band.
> >
> > There were some who said it could not be done. Well, it HAS been
done.
> > Do you understand this?
> >
> > Your acceptance of this kind of QRM is no longer acceptable to
> > reasonable amateur radio operators who now know that there is
this new
> > technology developed by Rick, KN6KB, the current Winlink 2000
> > programmer. I have personally tested it when he incorporated it
into the
> > SCAMP mode and it is superb.
> >
> > Most of us now expect (perhaps demand) that further development
with
> > automated digital modes and equipment will include the ability
to hold
> > off transmitting until the channel is clear. If this doesn't
happen then
> > the best that can be said is that these operations would have to
be kept
> > in small subbands, similar to the current fully automatic
subbands (that
> > also include the wide band semi-automatic operations).
> >
> > My preference, and I think you will find the preference of an
increasing
> > number of hams, is that any automatic operation that has no auto
detect
> > for a busy channel should be banned from the amateur radio bands.
> >
> > That is a very reasonable position to take considering the
available
> > software technology.
> >
> > 73,
> >
> > Rick, KV9U
> >
> > John Becker wrote:
> > > Lets try the guy 150 miles from you well within your
> > > ring of silence (you can't copy each other if you had to)
> > > listens to the frenquncy (unable to ask if the frequency
> > > is in use on every mode known to man) hears nothing.
> > > brings up the auto station and in doing so QRM's a QSO
> > > on the same frequency that he did not hear.
> > >
> > > Now as I see it that is not the fault of the auto station.
> > > But I know you are going to say that the auto station
> > > *should* be able to tell if it was in use. And that is getting
> > > real old with me.
> >
> > Need a Digital mode QSO? Connect to
Telnet://cluster.dynalias.org
> >
> > Other areas of interest:
> >
> > The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/
> > DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy
> > discussion)
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
>
>
> Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org
>
> Other areas of interest:
>
> The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/
> DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy
> discussion)
>
>
> Yahoo! Groups Links
>
Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org
Other areas of interest:
The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/
DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion)
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/digitalradio/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
