[Dstar] Re: D-Star and emergencies

[Mark Aitken]

dstar-request at lists.wia.org.au wrote:
>
> Hello All
>             Without going into the technical side of digital radio I 
>   
We are a technical hobby,  so why not go into it,  we may all learn 
something?

At the start I have to defend Dstar and say this.  With the reproduction 
of the audio, what do you
really want and expect.  I know of amateurs that want HiFi, Broadcast 
quality out of a 2.4KHz wide
SSB signal?????  What tha???

Think of what you are trying to achieve,  the normal human voice is 
roughly 300 - 3300 KHz, girls
and young men maybe a bit higher, we have 2.4Kbaud bandwidth to play 
with, take out FEC and sub channel
data from the 4800 Baud, so its not a great deal to play with.

Remember,  these radios are narrow band!!  Ever listened to a NBFM 
signal,  yuk.

> 1 = As you all have observed digital signals goes all garbled  under a 
> certain threshold where weak and noisy analogue transmissions can still 
> get thru 100 percent reliable messages under crucial times same for    
> very weak SSB signals on HF, Lives could be lost when sending a message 
> and if all goes all garbled while the person sending would have no idea 
> if the receiving operater has received the message this could mean waste 
> of valueable time lost if the mesage need to be sent again via another 
> mode such as straight FM,Same problem if a D-Star portable repeater go 
> off air and field stations having to go simplex.
>   
I totally disagree Lionel,  I have experienced the exact opposite. I 
have found that dstar will recover the
audio where a fm contact (mute open) was not workable.  QSB on HF can 
render any communication
unreadable,  be it analogue or digital,  even good ole faithful CW.

In portable, emergency conditions, even an analogue repeated can go off 
the air!  But I thought that the idea
of a repeated was to extend the range of transmissions anyway. So lost 
or garbled transmissions could and
would happen to either mode if conditions where THAT bad.


> 2 = As you can seen from that article from Utah when operating in noisy 
> conditions EG other people operating in the same room, voices of people 
> running around under emergency poeple could very vocal,
> cracking of fires in the background, noisy generators ETC ETC could make 
> hearing the operator non understandble during exchange of messages.This 
> problem is worse on digital than Analogue.
>   
I have works a few contests, not as many as most but I personally 
dislike a multi operator station due to
the back ground noise in any circumstance.  This form if interference 
can happen to either analogue or
digital, and I reckon correct choice of microphone, headphones etc can 
help in preventing such occurrences.

Again,  from experience,  anyone traveling in a car with the window down 
holding a qso can once again yield
background noise interference be it ssb/fm/dstar.  In saying that,  I 
will say, in my opinion,  the qso's that I have
had with mobile stations in this exact situation on dstar have not been 
that affected by road/engine/wind noise.

> 3 = Having to program your digital radio on the fly and having to wait 4 
> seconds to break in on repeater would be a pain in the backside and 4 
> seconds is a long time under extreme conditions.
>   
Every piece of new technology requires the user to "figure" out how to 
operate it to get the most out
of the piece of equipment.  Dstar radios are not alone in that respect.  
But, I have no more trouble with my
ID800H than I do with my IC706MKIIG both home base and mobile. I will 
give in that there is no substitute
to having the approbate cable and a PC to set it up nice and easy, in 
fact this is my preferred method, yet, I started
out with no cable and no software yet was able to, eventually, set up 
from the dial and buttons and really,  a new repeater
doesn't take more than 1 or 2 minutes to install from the front panel.

To further add to this point, if you are involved in emergency work,  
you should be trained, for your own and others
health and safety, this means also with procedures and equipment.  So 
why would you as a prospective emergency
communications officer during a natural or other disaster jump head long 
into your job not being familiar  with the
procedures and equipment you are going to be asked to utilize!

I will have to agree though that I personally think the 4 sec rule is a 
bit of an ask however, in the 12 months odd
the operators in and around Melbourne have become used to this procedure 
and generally things work smoothly.


> To finish I am not trying to bash D-Star I enjoyed working USA last 
> night but I would  never use D-Star for real WICEN emergencies it is 
> just not suitable when there are people lives at risk.
>   
I am not bashing any other mode either.  I enjoy working dstar simplex 
better than via a repeater, this way I can test its
capabilities better than with a S9+60db signal that will NEVER be pushed 
to the extreme.

Not bagging all the great work that WICEN and other organizations around 
the world do and achieve each and every
day, however, at least in VK3, the emergency services learnt hard and 
fast in the early 80's what a strong and reliable
communications network could do to prevent the loss of life. And I think 
they have their act together pretty well these days.


> 73 Lionel VK3NM/VK6DC
>
>   
73

Mark VK3JMA