[amsat-bb] Re: OH2AUE P3E transponder demo video

Gus 8P6SM 8p6sm at anjo.com
Thu Oct 18 07:55:01 PDT 2012

On 10/18/2012 02:47 AM, Gordon JC Pearce wrote:
> On 18/10/12 03:28, Gus 8P6SM wrote:
>> On 10/17/2012 05:38 PM, Gordon JC Pearce wrote:
>>> We're going to have to try coming up with clever satellites, rather than
>>> flying a bent-pipe box the size of a fridge.  No-one is going to want to
>>> lift that, without us paying full price.
>> I may not be 100% on the 'bent pipe' definition, but if it means hams
>> 'talk' on the UP and other hams 'listens' on the DOWN, then that's what
> What I am referring to is linear transponders.  They're heavy and
> consume a lot of power.  We need to either devise a new way of doing
> that, that doesn't involve heavy inefficient linear amplifiers, or stick
> to something like FM or GMSK where a little lightweight PA that doesn't
> dissipate most of the input power as heat will do the job.

A full-duty-cycle FM transponder that eats up the entire bandwidth of
the satellite to allow a single ham to communicate strikes me as far
less sensible than an efficient linear transponder that allows multiple
simultaneous contacts and does not run the PA at full duty cycle.

But never the less, I don't really care what the operating mode for
communication is, so long as there actually *IS* an operating mode for
communication.  Satellites that DON'T allow hams to communicate are not
of any interest to me, and (IMHO) are not relevant in any discussion of
AMATEUR satellites.

>> we need.  Whether it be the size of a fridge of a matchbox, if ham radio
>> operators can't use it to communicate, then it's pretty pointless.  It
> If it's big it won't fly, unless you pay for the whole flight.  Have you
> noticed how airlines have stopped carrying children for free, too?

And most people have long ago stopped whining about it and now simply
pay for their children to fly.  So let's pay for a flight and stop
whinging about how we can't get a free one.

>> don't matter how much telemetry it sends, how many LEDs it blinks, how
>> clever the beacons, or what purty pictures it downlinks.  If hams can't
>> use it to QSO, then why bother?
> It depends what you're trying to achieve.  I'll respond to Domenico's
> comments here, too.
> Most satellites are not built by radio amateurs.  They're not there so
> you can talk to your friends.  They are built so the engineering
> students that will build the satellites and spacecraft of the future.

Most satellites have nothing whatsoever to do with the engineering
students of the future.  But we don't get all goo-goo eyed over the
launch of some military spy-sat because it has nothing to do with
amateur radio.  And neither do most of the cubesats.

> Like it or not, amateur radio is a secondary service on 70cm.  We don't
> own that chunk of band.  If you want to work a band free from "beep
> sats", stick to 2m and good luck with your build.

Uh-oh!  As a recent posting leads us to understand, UMSATS TSat-1 uses
437 *and* 145 MHz amateur radio bands.  Is the 2 meter band a secondary
service as well?

73, de Gus 8P6SM
The Easternmost Isle

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