[amsat-bb] Re: All Satellites

Andrew Rich vk4tec at tech-software.net
Mon Sep 28 03:29:05 PDT 2009

I am playing with RF modules that take ms to send not seconds



Andrew Rich
Airways Technical Officer Grade 4
Surveillance - RADAR ADS-B
Amateur Radio Callsign VK4TEC
email: vk4tec at tech-software.net
web: www.tech-software.net
----- Original Message ----- 
From: "William Leijenaar" <pe1rah at yahoo.com>
To: <amsat-bb at amsat.org>
Sent: Monday, September 28, 2009 8:04 PM
Subject: [amsat-bb] Re: All Satellites

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 ?

Besides the technical difficulty there is also the (human) organising 
factor. I heared some ideas about an easy to access geostationary satellite 
with high power downlink. That would be great, but without any communication 
control it would be like the FM LEOs where everyone talks at the same time 
and nobody is able to get there message through.
It might be solved with a central control centre on a safe place (maybe by 
the Amateur Radio Emergency Service ?) that has control over the satellite 
radio and uses it as a remote radio "ear" in space. In this way it is also 
possible to use one frequency simplex system.

Just some ideas,

73 de PE1RAH,
William Leijenaar

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