[amsat-bb] Re: Icom D-Star

[Tony Langdon]

At 01:42 AM 4/24/2011, Gregg Wonderly wrote:
>In the end, digital compression of spectrum space is going to happen more and
>more.  AM style broadcast is hugely inefficient even though it is painfully
>simple to do.  I don't really believe that D-Star is the right choice for
>"everything" because it is single source.  But, so is Microsoft windows,

There's no "one size fits all.  D-STAR has its place, and being the 
new kid on the block, it's open to a lot of tinkering.

>MacOS-X, and many other software based systems.  If you are an FPGA 
>programmer,
>perhaps you can build an FPGA based CODEC for amateur radio that 
>would do voice
>compression etc.  But in the end, you also have to have an 
>transmitter with the
>appropriate bandwidth output to reduce the spectrum used.

Well, maybe one day someone will package something like Codec2 into a 
chip.  That will be a good day for ham radio, BUT it'll never make 
D-STAR.  Why?  Because it's not in the spec and will break the 
existing installed hardware base.  However, the future is likely to 
consist of "multimode" radios, which can handle multiple codecs and 
protocols, and which will be capable of having a yet unknown cocecs 
installed in the field.  Also, eventually the DVSI patent will run 
out, just like the patent for SSB did many years ago.

>The simple fact is that HAM radio emission standards (simple voice modulated
>with some simple emission standard) are now more than a century old.   As

Not quite.  CW certainly is, AM is around the century mark, I think 
SSB is a little over 80 years old from its first conception, and FM 
is 75 years old. :)

>capable as they are, the abilities they present seem minimal to 
>some.  I think
>that there are great things about them because they do allow long distance
>communications which the HAM community regularly uses to support distant
>operations which provide aid to areas struck by natural disaster.

I think this is one area where ham radio will be increasingly 
important.  Alongside the newer modes, it can also be a living 
"museum" where older modes can live on.  The only mode that hasn't 
survived is spark gap Morse, because it's so spectrally inefficient 
it became illegal.  So ham radio, while it still does advance the art 
also preserves the art as well, and both are important functions to 
me.  If something happened that required falling back to older analog 
modes, there's a pool of experienced operators on hand, who know he 
quirks that the commercial world will forget.


>But, we all have to understand that it costs money to do anything "new and
>different".  People experimenting with stuff is great, but it 
>minimizes who can
>participate if you have to "build it" or "pay a lot".   That's just life in
>general.  You can't participate in everything unless you have the 
>resources to
>do that.

And there's experimentation.  I don't have the background and 
resources to play at a low hardware or software level, but at a 
higher level, equivalent to "mashups" on the Internet I have played 
and still do.


>In the US, any digital communications that is coded in some way only needs to
>have a publicly visible document detailing how it works for the FCC 
>regulations
>to be met.   Other places in the world may have different requirements and
>that's nothing new is it?

Requirements here are much the same as the US, somewhat more liberal 
when it comes to modulation and coding.  Basically there are two 
things that matter.  (1) Not to exceed the maximum necessary 
bandwidth (D-STAR fits on all bands except 2200m), and (2) The coding 
must not be for the purpose of "obscuring the meaning of the 
message".  D-STAR certainly fits, because radios are readily 
available, and they don't need encryption keys.

73 de VK3JED / VK3IRL
http://vkradio.com