Kris Kirby wrote: > 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.
It is openly available on a number of coordination websites. Coordinators (in areas where coordinators are actually alive and paying attention) have been planning for narrow-band digital and other narrow-band technologies for years. The assumption that D-STAR only takes up 6 KHz is flat-out wrong, too. Folks HAVE looked at it now on spectrum analyzers, and most tend to agree with 10 KHz is the minimum spacing between two D-STAR systems. But there's not a lot of data (yet) on this. With P25 out there too, most areas are using 12.5 KHz spacing so D-STAR and P25 can play nicely together in a sub-section of the spectrum side-by-side, without bothering each other, but still being 1/3 more spectrally efficient as a standard 16 KHz wide (5 KHz deviation) analog signal. Here in Colorado, there is already a "narrow band digital" sub-section of the repeater spectrum for UHF and up, and digital machines that can do these narrow technologies are being coordinated there. Both a private P25 system and a D-STAR system are already in those allocated areas. Work on this takes a while, but started here more than two years ago. VHF is still "full" here, and recommendations for creative ideas haven't been formalized. Efforts are underway to remove the "paper" machines to make some room, and maybe... just maybe... some smart "shuffling" will be needed to get things "right". No one really knows yet, but a lot of smart folks are thinking and working on it. The answer is... don't buy repeater gear expecting a VHF coordination on ANY mode right now in the Denver Metro area. Outside that area, things loosen up considerably. D-STAR, Analog, P25, or otherwise. >> 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. Yep. Long-term, individual hams getting "deals" from friends for sites, or clubs paying money to be on commercial sites, is the norm. Been that way for a couple of decades now, not sure what the surprise is there... or what it has to do with narrow-banding Amateur technologies? Building to commercial standards is now fast-becoming a requirement, not a luxury. Isolators are expensive, but lawsuits when you jam the local Public Safety frequencies will cost a lot more. "Best practices" must be followed by hams, we don't get any special dispensation not to do our engineering properly. >> 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 real difference for D-STAR is two-fold. The data capability is built into the rig. The programming cable (at least for the portables, the mobiles need a different cable that anyone can make...) doubles as the data cable, so you buy the programming software, get the cable with it as a package deal, and five minutes after programming your rig, you can also have the various applications that people are writing for communication over the 1200 bps channel downloaded and running. No TNC, no need to learn anything... it's just "done". Add in a Gateway, and you can now (as of today) send that data and voice at the same time back and forth between you and your buddy somewhere clear across the country, by just changing a callsign "route" in your radio. It's the "pre-built" integration between all of the things you mentioned (data systems, voice systems, internet linking systems) into one contiguous system that "just works". All you need is a compatible rig. > 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. The plus of digitizing the voice at the user rig and receiving that digitally at the repeater is this... ever spend an hour getting levels set right at multiple ends of an analog voice linking system? Some systems certainly don't do it right and sound like crud, and/or have other technical issues (too many hops, too much high-pass filtering, etc...) that makes the linking sound bad. Still works for communication but... it's nasty. (Hanging my head in shame here, some of my links sound like crap too.) With digital systems, be it D-STAR, P25, or anything else... the system digitizes you at the source and the only variation in your audio end-to-end is your microphone in your rig, any packet/stream loss, and the Vocoder the system uses. You sound the same coming out the other end, no matter what. That's probably one of the "hmm, I didn't think about that" things that came to my mind once we started playing with our Gateway. Everyone sounds the same, and a conversation with someone here locally is the same audio as a conversation with someone in California or Australia. I have noticed SOME difference with the DV-DONGLE product -- the quality of the PC/Mac/Linux microphone is key there, but usually the DONGLE users sound BETTER than the built in mics in the Icom rigs. (One of our local users is convinced the mic in his IC-800H sounds worse than the mic in his IC-92AD, so he's working on fixing that audio... we'll see how he sounds when he gets through the bench work and comes up with a theory as to why the Icom hand mic sounds bad to him. So there ARE differences, but generally with digital... what goes in, is what comes out. That's NICE for a large linked system.) > 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. Cool! We have a lot of "duplicated coverage" repeaters out here with our high mountain sites, but I've learned that some hams just can't seem to get along with others on-air... having them not on the same analog system is a good thing for sanity. But... in a digital system, they could easily set up a digital squelch or talk group (depending on if you're talking about D-STAR or P25, or whatever... they all call it something different, but at the low-level, it's just twiddling a few bits and deciding if your rig is going to listen if those bits are twiddled), and share the same repeater, and never hear each other if they didn't want to. The only problem then (like in all muxed/shared data networks) is managing overall system load and adding more repeaters to cover the traffic load. >> 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". Politics. Get the "repeater clique" interested, and things start to move. Our association, Colorado D-STAR, went a long way towards that... various ARES, Repeater Clubs, and technically minded individuals pitched in together to get the first system up. Now two other clubs have formally announced either systems are purchased or they're actively accepting donations, and others are interested. The system has been up only a week at a low test site, and we have almost 30 registered Gateway users. Interest in digital tech is there, but if the repeater-builders of the world don't go build... the interested people who might otherwise buy a rig and start experimenting, or even just talking on it and enjoying it, sit stagnant. > And again, this is just a hobby, even though some people choose to live > and breathe it. You should meet a few Private Pilots, if you think we hams are "bad". Some hobbies are just more of a "lifestyle" choice than others. You can't be a safe/good pilot without flying a lot, and to fly a lot costs a lot of money and time at the airport and in the aircraft... for example. Ham radio is unique in that you can really dive in deep, or you can just operate casually once in a while. Your choice of how involved you are in things can vary from minute to minute, year to year. It's so broad, no one can "do it all". As a "generalist" I like it all, but don't have time to do it all... right now, it's D-STAR and fixing some analog repeater links... later in the summer it'll be VHF and up weak-signal, maybe by fall I'll get better HF antennas up... who knows? As long as I'm having fun and not neglecting my normal life... just like any hobby... I just keep doing it. When it gets "not fun", I don't. There are certain aspects of repeater operation of ANY kind that are almost always NOT fun, though... comes with the territory of building "infrastructure" for others to use, I guess. :-) Nate WY0X
