Bruce Robertson wrote:
On Mon, Sep 28, 2009 at 7:04 AM, William Leijenaar <pe1...@yahoo.com> wrote:
Hello AMSATs,
I agree that APRS can have a higher power transmittter, because of its small
amount of time to get the data broadcasted. However the workability with the HT
and whipe antenna is only an advantage for the downlink. For the uplink there
will be no advantage.
Personally I believe that making a satellite easier accessable will also decrease its
functional efficiency. This is especially the case for satellites with limited user
access, like single channel FM satellites. This also includes APRS. The same issue is
valide for a geostationary satellite, with the addition that a geostationary satellite
would be overloaded in short time by more and more stronger stations as fixed antennas
can be used. Only the uplink power level would be the parameter of
"competition". Resulting in a privat chat satellite for only few (high power)
users.
Satellites for emergency communication sounds very interresting, and personally I believe
it can give a great advantage when doing it well. The question is only what will work
well in an emergency situation. It will depend on the needs and the availability of
equipment in the effected area. I believe that digital communication will be of limited
use as you need also a computer, modem, keyboard, screen, software etc besides your
radio. Only one thing missing and you will not be "heared". I don't say it is
impossible, but to make the system work the ground stations need to be made more easier
somehow. Maybe HT APRS in combination with voice to text conversion (and opposite) would
be an idea ?
In some cases, the groundstation situation might not be as complicated
as you describe. The popular TH-D7A Kenwood HT, though no longer
manufactured, has integrated APRS messaging with a TNC on board. So,
too, does Yaesu's new VX-8R. And there are mobile 2m radios with
similar capabilities. Moreover, if there were a wide satellite network
of APRS birds, we could hope that even more new HTs would include this
feature, since the cost of implementing a modem is quite low these
days.
Not to be picky but the VX-8 do not have an inbuilt TNC but it has a
"TNC" doing APRS and could not be used to connect to a computer.
But i think that APRS is a nice function for the sats. It's easy to use
and you can do i.e e-mail too. It's easy to operate and requires very
little hardware to operate.
APRS is a nice mode to allow more people use the same "bandwidth". Doing
the sats portable with voice is not always an easy task if the majority
is using rotators and high power.
I really would like more APRS sats and more "igates" as i'm happy with
messaging capability and positioning.
Most new tracker like TinyTrack etc have message and display capability
so that you don't need a special made APRS radio.
Kai Gunter
LA3QMA
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