1 Sep
2017
1 Sep
'17
12:11 p.m.
Y'know, there is some relevance in a
significantly asynchronous circuit
with this stuff.
I think the correct label is "asymmetric" but many people call it
"asynchronous"...
Put the High speed TX on the top of the mountain and
have it push high
speed frames in broadcast or multicast mode whilst the outlying stations
listen to the stream and write down the packets relevant to them.
This is of course what I had in mind. We don't have any mountains here but we
have a 3cm ATV repeater at 220m in a broadcast tower transmitting a DVB multiplex
where we could use some bandwidth (or e.g. the bandwidth remaining after the
several variable-rate encoded ATV channels have had their share) to transmit
IP over DVB. Both broadcast/multicast traffic (like IPTV streams from the repeater) and
traffic to a single endpoint (after all, we do not hide traffic from eachother).
The return channel could be much slower indeed, depending on the kind of traffic
and the required return traffic. Maybe even a 9600+ baud packet link, or one of
those newly developed 70cm links of about 400kHz width.
At the moment the repeater is not operating, but we are working on getting it back
on the air.
Rob
1 Sep
1 Sep
12:26 p.m.
New subject: OFDM Modem
Just remember, in the US, that 70cm data must fit in 100 kHz and be 56
kbauds (Same on the 219 Mhz band), but this is interesting work. 97.305(c)
and 97.307(f)6
On Fri, Sep 1, 2017 at 9:11 AM, Rob Janssen <pe1chl(a)amsat.org> wrote:
Maybe even a 9600+ baud packet link, or one of
those newly developed 70cm links of about 400kHz width.
--
------------------------------
John D. Hays
K7VE
<http://k7ve.org/blog> <http://twitter.com/#!/john_hays>
<http://www.facebook.com/john.d.hays>
1:37 p.m.
New subject: OFDM Modem
On Fri, Sep 1, 2017 at 9:26 AM, K7VE - John <k7ve(a)k7ve.org> wrote:
Just remember, in the US, that 70cm data must fit in
100 kHz and be 56
kbauds (Same on the 219 Mhz band), but this is interesting work. 97.305(c)
and 97.307(f)6
John,
Isn't this rule moot when the data is multiplexed on an ATV
transmission? That is the most interesting detail of this
implementation to me.
Tom KD7LXL
1:46 p.m.
New subject: OFDM Modem
Why do all new-technology discussions about the ham bands degenerate
into arguments about USA rules? No wonder most innovation takes
place in other countries.
- Brian
On Fri, Sep 01, 2017 at 10:37:15AM -0700, Tom Hayward wrote:
On Fri, Sep 1, 2017 at 9:26 AM, K7VE - John
<k7ve(a)k7ve.org> wrote:
Just remember, in the US, that 70cm data must fit
in 100 kHz and be 56
kbauds (Same on the 219 Mhz band), but this is interesting work. 97.305(c)
and 97.307(f)6
John,
Isn't this rule moot when the data is multiplexed on an ATV
transmission? That is the most interesting detail of this
implementation to me.
Tom KD7LXL
1:55 p.m.
New subject: OFDM Modem
On Fri, Sep 1, 2017 at 10:46 AM, Brian Kantor <Brian(a)ucsd.edu> wrote:
Why do all new-technology discussions about the ham
bands degenerate
into arguments about USA rules? No wonder most innovation takes
place in other countries.
- Brian
Rhetorical? I'll answer anyway...
In the context of data emissions (like we would expect on this mailing
list), it's because the USA rules are so limiting. Every new
technology is an exercise in squeezing into the old rules. This method
of packing data into an ATV transmission--which is the one exception
for high bandwidth on 70cm--is engenius.
And yes, it is no wonder most innovation takes place in other
countries given the limits imposed on lower frequency data
transmissions in the US.
Tom KD7LXL
3:04 p.m.
New subject: OFDM Modem
A few decades ago, I was one of a handful of people included in
a Special Temporary Authority (STA) permitting the use of spread
spectrum on the ham bands. It was astonishing to me how much
opposition from the ham community itself we encountered trying to get
that exception to the rules approved.
I think to a large extent we could get the FCC rules brought
into at least the previous century, if not this one, by a
concerted effort to get them changed. But in general, hams in
the USA don't work together, and we have no national organization
in favor of getting such changes made, so that is not going to
happen.
Some day I would hope we would be able to do something about that.
In the meantime, both STAs and the Experimental Radio Service are
legal ways around the stupid rules we have to contend with. Both require
a lot of paperwork.
But that's enough of USA rules problems; this is an international
mailing list and I'm often encouraged by what people elsewhere are
doing. Keep up the good work, folks.
- Brian
PS: in Southern California, 70cm is so eaten up by military radars
and other transmission stuff that it's really not very usable
for anything beyond FM voice repeaters anyway.
On Fri, Sep 01, 2017 at 10:55:11AM -0700, Tom Hayward wrote:
In the context of data emissions (like we would expect
on this mailing
list), it's because the USA rules are so limiting. Every new
technology is an exercise in squeezing into the old rules. This method
of packing data into an ATV transmission--which is the one exception
for high bandwidth on 70cm--is engenius.
And yes, it is no wonder most innovation takes place in other
countries given the limits imposed on lower frequency data
transmissions in the US.
Tom KD7LXL
2 Sep
2 Sep
6:47 a.m.
New subject: OFDM Modem
On 2/09/2017 3:46 AM, Brian Kantor wrote:
Why do all new-technology discussions about the ham
bands degenerate
into arguments about USA rules? No wonder most innovation takes
place in other countries.
Probably says a lot about the US rules. There seems to
be a lot more
restrictions on emission modes than most other countries these days,
especially on HF.
--
73 de Tony VK3JED/VK3IRL
http://vkradio.com
8 Sep
8 Sep
12:39 a.m.
New subject: OFDM Modem
On Fri, 1 Sep 2017 18:11:03 +0200, Rob Janssen <pe1chl(a)amsat.org>
wrote:
One could go with asymmetric but Aloha was tested in two modes,
asynchronous-asymmetric where the Menehune was master of the output
channel and terminals contended "asynchronously" on the input without
being able to hear each other and slotted Aloha where Menehune
assigned time slots to terminals and they sent their data
isochronally. I believe there was one slot kept open where a
previously idle terminal could contend for assignment of a slot.
Slotted Aloha performed better than asynchronous Aloha.
--
Geoff Joy - ke6qh -
AmprNet IP Address Coordinator for San Bernardino & Riverside Counties.
(44.18/16)
Y'know,
there is some relevance in a significantly asynchronous circuit
with this stuff.
I think the correct label is "asymmetric" but many people call it
"asynchronous"...
2444
days inactive
2451
days old
7 comments
6 participants
participants (6)
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Brian Kantor -
Geoff Joy -KE6QH- -
K7VE - John -
Rob Janssen -
Tom Hayward -
Tony Langdon