[QCWA] D-Star experience

[Jeffrey D Angus]

Daron Wilson, N7HQR, sent me a response about D-Star and asked that I 
post it here:
> I operate a VHF Dstar repeater on Mt. Hebo, as well as the internet gateway,
> and have done a fair amount of field testing.  In short, while the system
> may work well in a dense, cellular linked design, the digital signal is
> horrible anytime you have multipath such as on the coast where we have trees
> and mountains.  The specific design of the protocol causes huge holes in the
> voice/data stream when the data is corrupted.  Other digital protocols
> recover very quickly, only losing a syllable or so, but not D-star.  Another
> complication is allocating spectrum, as the chair of the coordinating body
> in Oregon, we struggle to find a spot in the VHF spectrum for the repeaters.
> Unfortunately they are advertized as 6.25khz channel devices, which might be
> the case for other digital services, but when sharing with analog users it
> won't work to put them between existing analog machines.  Mine remains
> operational with very little use, it does well for fixed stations with ample
> signal, but the UHF analog repeaters on the hill serve us much better than
> this digital VHF.
>
> As you might be aware, there are two data modes, low speed and high speed.
> The low speed data is interleaved in the digital voice stream, and is
> similar to the APCO P25 protocol in that manner.  Operationally it is
> similar to a sub carrier on FM or a sub audible tone on analog FM, WHILE you
> are talking, there is a slow stream of data.  It works well for sharing GPS
> coordinates for example, as I am talking with you on Dstar there is enough
> data ability to send you my position.  Of course no error correction to
> speak of, so you get what you get.  Dan KK7DS has exploited this amazingly
> with his D-Rats software, allowing the sharing of data with complete error
> correction, integration of ICS forms, maps, and more.
>
> The high speed data is nothing more than an Ethernet bridge on 1.2 Ghz,
> operating in a simplex mode.  We have one on Mt. Hebo, and use it to link to
> several EOC's.  It does very well in a point to point setting, we tested
> from Mt. Hebo to Goat Mountain, over 70 miles with 10 watt 1.2 Ghz radios
> and were able to get new full bandwidth.
>
> Washington County had some incredible building with the technology, likely
> due to the highly technical environment in that area.  A large grant was
> procured to link the various neighboring counties together.  I participated
> in many of the planning meetings, which were mostly made up of ARES EC's
> from the various counties involved.  A very workable network was presented
> by Dan KK7DS, but after months of trying explain how it would work to the
> ARES folks, they just could not grasp the data and networking concepts.  Dan
> and I worked closely with the county to arrange for sites for the equipment
> and redundant linking for file sharing between the nodes.  In the end, the
> ARES folks just couldn't get it and finally decided to spend the money on
> Alinco radios and 1200 baud modems.  (and we wonder why we can't move
> forward in amateur radio technology?)
>
> Currently, Washington County uses the technology on the low speed data side
> of things with D-Rats, however there isn't any growth and most of us who had
> the ability to build and grow it have given up trying to drag people into
> the value of the technology.  Dan and I are working on a network to link the
> coast and the valley with high speed, and move towards an IP based solution
> with some of the linking operating over high speed Dstar links.
>
> There are many formats available, several will grow while others will
> dwindle off, and unfortunately few of these decisions will be made because
> of quality or technical superiority.  Remember, while Betamax was superior
> to VHS, the porn industry drove VHS to the top making it the winning
> solution.  Dstar was a Japanese design that they just tossed to the US
> because they already had it, it is in no way a superior digital solution.
>
> BTW, the Chinese aren't 'cloning' systems and selling them, they are
> stealing the design from Japanese companies, stripping out every possible
> component that isn't required to make it appear to function, and then
> selling it to us as 'equal to' the Japanese product.  I purchased a couple
> of the different ones on ebay to evaluate, you can pick up the image
> frequency with as much clarity as the desired frequency and the radios are
> useless next to other transmitters due to little or no filtering.  I keep
> them around as great examples, and show folks the difference.  With an Icom
> handheld and the Baeofing handheld, I work FM satellites with a hand held
> antenna, but it only works if you receive on the Icom because if you use the
> Chinese radio to receive, the VHF transmitter just clobbers it.  Not a
> 'clone' by any means.
>
> For amateur radio, the biggest issue with emcomm is not interoperability, we
> can all talk to each other on many different bands and modes (provided the
> operators are skilled).  The problem is lack of standardized training, and
> accepted certification for operators.  Every other participant in
> emergencies has a firm requirement (volunteer fire fighters, EMT's,
> paramedics, reserve police, even CERT has a 24 program that must be passed)
> yet amateur radio plugs along with the ARES requirement of 'willingness to
> serve and a license'.  We have grown in numbers, which is fantastic, but now
> we have literally hundreds of 'hams' with a Wouxon handheld, preprogrammed
> by their group leader who are ready to help.  Many cannot program in a new
> frequency, or even leave the VHF/UHF FM band.  If we are to be taken
> seriously, we need to have some required, standardized training and
> certification for our folks that shows they can do what is needed.  We need
> to make these new operators into hams so they are frequency agile, and mode
> agile, making us as valuable as possible to the served agencies.
>
> 73
>
> Daron Wilson, N7HQR
>
> www.oregonaces.org
> www.ocrg.org
> www.orrc.org
>