[amsat-bb] Re: Help sought - amateur satellite service vs D-star

Geert Jan de Groot pe1hzg at xs4all.nl
Wed Sep 9 03:06:16 PDT 2009

[Apologies as it's slightly off-topic, I do my best]

On Wed, 09 Sep 2009 16:39:20 +1000 Tony Langdon wrote:
> >The folk experimenting with D-star
> >on 70cms use a fairly large shift of 9.4 Mhz, resulting in
> >a typical setup of 430.400-430.600 in and 439.800-440.000 out.
> >Unattended stations (like D-star repeaters) do require a special
> >license here.
> OK, so what do FM repeater owners do?  Asking that, to see if there's 
> any other places the D-STAR systems can be put.  Over here, D-STAR 
> repeater allocations are in the same parts of the bands as FM ones.

Good question, long and complex answer. Briefly, (voice) repeater pairs
are allocated geographically. So, there is one slot (but only one slot)
per area. If there are multiple groups who want to build a repeater,
then the single license would alternate between these two groups
every three years.

On 70cm, voice uses 1.6 MHz shift down. The repeater I built (PI2EHV)
does 431.700 in, 430.100 out.

D-star is currently considered "digital/packet" for which the
9.4 MHz shift pairs are set up. And the output collides with
the newly "allocated" DGPS users. Hence, no new licenses are issued,
and the D-star folk are looking for a new place.
Which is all nice and well, but the "new place" SHOULD NOT
be in the sat band for all the reasons you mention, 
and I believe they should be told.

I've repeatedly asked why they are so hang up on large shifts
(causing them to need to take this extreme measure), but I get
no answer. To me, the difference between GMSK and NBFM is small,
and if 1.6 MHz shift can be made to work for NBFM, it can be made
to work for GMSK.
And, obviously, a smaller shift gives much more flexability to
(potentially) find a good spot. [that is, if we would decide to
accomedate the illegal allocation for DGPS, which I don't think 
we should, but that's another matter].

Anyway, the current proposal would hurt the amateur sat service,
*as well* as negating a careful allocation process the amateur
radio community has built for tens of years.
While the proper allocation of this mode is beyond the scope of
the AMSAT community, the current, improper proposal *is* within
scope, and I hope people will raise their voice on this.


Geert Jan PE1HZG

More information about the AMSAT-BB mailing list