[amsat-bb] Re: All Satellites

Kai Gunter Brandt kai.brandt at cih.uib.no
Mon Sep 28 05:46:05 PDT 2009

Bruce Robertson wrote:
> On Mon, Sep 28, 2009 at 7:04 AM, William Leijenaar <pe1rah at 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

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