On Fri, 16 May 2008, Ron Wright wrote:
> For D* there is the one issue of less bandwidth. D* occupies about 6
> kHz, about 1/3rd that of analog allowing for putting 2 D* in same
> space as 1 analog. This is not including what can be done with
> digital such as putting more than one set of users on one repeater
> using TDMA or some sort of multiplexing like is now being done I think
> with P25 in the Comercial world. These are starting to show up from
> the Comercial world to Ham Radio, but much more can be done. It has
> been done by the cel phone industry for over 15 years...it is old to
> them.
It would be nice if existing efforts to install D-Star repeaters made
use of this fact. Some spectral analysis information should be collected
and made openly available. I would like to note that I am not in favor
of modification of the existing limits set in the two meter band plan. I
feel I did not make that clear in my last message.
> I think we as hams who have among us some very experienced people who have
> dealt with digital comm for years in the Comercial world (2m/440, etc analog
> came from Comercial world, just we Hams wanted more than "get input/key
> repeater" and added all kinds of bells a farts) we can put together systems
> that can be squeezed into the existing freq allocation.
If we as hams really went the extra mile to ensure our repeaters
generated no mixing products or spurious signals, we would all be broke
at the cost of one $1,500 circulator for two meters. Combining systems
are unfortunately the way of the future as most if not all tower sites
are becoming commercial sites charging rent to anyone and anything that
has a feedline and an antenna.
> Digital is going to revolution voice comm at least on VHF and above.
> A well engineered open Internet interface will be an added feature
> that will also revolution voice and data. We can go to CA or VA or IL
> and using a local repeater there comm with our home repeater just as
> if we were there and this will route things automatically. A feature
> the comm world has been working on and doing for a number of years
> although from my understanding has had slow progress.
I just don't see the revolution myself. We've had HTs that had the
capability to do APRS for several years now, and we've had the ability
to build all the data networks we wanted to with packet radio at 1200
bps and 9600 bps. 9600 bps required radio modification, however looking
at the history of land mobile, the Motorola Spectra has been able to
pass 9600 bps packet data for the better part of the 1990s. The 9600-bps
capable ham rigs, on the other hand, have only been around since about
1996 or so.
The difference between digital NOW and digital THEN is that now we're
digitizing voice, chopping it up, and sending it over the air in a
digital packetized format. Whereas before, it was voice on one channel,
and data on another, with the data being keyboard to keyboard or
keyboard to BBS only. Even now, there are few good reasons to build and
install a repeater based on D-Star -- ultimately, it is just building
the infrastructure to support the existing community of users or future
users.
I am a repeater trustee myself, and the repeater I operate covers a
range that only one other repeater covers -- however, that repeater has
several remote recievers and due to the wide coverage afforded, may not
be the best choice for a small localized event like a bike race or
charity walk. I did analyze the existing location and the map of nearby
repeaters before making the effort to restore the repeater to operation.
Our location affords us protection from outside interference, as well as
covering a relatively small patch of the earth that few nearby repeaters
cover as well.
> However, there are draw backs with digital and I'm not talking about
> the high cost we see now. Experience will lead to these draw backs
> and solutions. Can't fix a problem if one does not know it exist or
> what is a problem.
The land mobile guys have seen this already with simulcast and voted
networks of repeaters running digital trunking modes. There are a few
new papers out there about implementing the systems and the caveats of
doing so.
> What I'm trying to say D* offers opportunities that will allow it to
> come into the analog world and make better use of spectrum allowing it
> to better and more efficiently use what spectrum we have now. The
> main obstacle are the ones wanting to stand still.
This is unfortunately true. Hams are an obstinate group -- to suggest
one clear a frequency for experimenting with a new mode such as D-star
in a place like New York City would likely get one laughed at, in
another part of the US, would cause one to become engaged in a grudge
match with the existing "repeater clique".
There's no perfect solution, other than what we do with our repeaters
already -- compromise.
And again, this is just a hobby, even though some people choose to live
and breathe it.
--
Kris Kirby, KE4AHR <[EMAIL PROTECTED]>
But remember, with no superpowers comes no responsibility.
--rly
