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Re: Frequency Co-ordination.




On Jun 16, 2008, at 3:54 AM, John Hackett wrote:

> Can you imagine a future scenario....not too far in the future.
> 'Linear transponders on 2m & 70Cms?'.... don't be silly, those are the
> Cubesat bands :-).

While I don't question the utility, or even the necessity of frequency  
coordination as part of the amateur satellite service, I am honestly  
confused about some of this.   If I recall correctly, 144.3 to 144.5  
and 145.8 to 146.00 are allocated to the amateur satellite service.   
That's at best 400khz of space available to us for all satellite  
operations.  It isn't hard to imagine that a single satellite could  
actually cover each of the sub bands with a single linear transponder:  
for instance, AO-40's 2m uplink was 145.840 to 145.990, covering  
nearly 40% of all spectrum available on 2m to the amateur satellite  
service.   The new Phase 3E satellite has a proposed passband from  
145.845 to
145.945 (according to http://www.amsat-dl.org/p3e/tabelle.htm).

And here's the thing: VO-52 already operates on 2m, centered on  
145.900.  DO-64 is carrying a
linear transponder centered on, you guessed it: 145.900.   Right now,  
that's not such a big deal.  DO-64 isn't on yet, and they are both in  
LEO orbits, so the chance of them both being up is relatively small  
for any particular pass (indeed, running a simulation forward, I found  
no conflicts between DO-64 and VO-52 in the next 30 days from my home  
location).  Both of these satellites had frequencies coordinated  
through the IARU.

But if we do succeed in getting a satellite into HEO, it seems to me  
that we already have a problem: I suspect that it renders the LEOs  
transponder capability more or less moot.  The simple fact is: there  
isn't that much space available to us on 2m, and it fills up quickly,  
coordinated or not.

We've also seen that even though the COMPASS-1 and new CUTE-1.7+APDII  
sats were coordinated, they actually were coordinated to use the same  
downlink frequency and were launched on the same vehicle.  This isn't  
all that big of an issue, their orbits are drifting apart, and they  
use primarily narrow band CW telemetry on those frequencies, but  
still, potential conflicts exist.

I guess my question is: how did these conflicts make it through  
frequency coordination.  Also, how do  sider allocations get  
processed?  Everybody seems to want more linear transponders on board  
(we have seen this request again in response to the Spanish cubesat's  
request for comments) but if we were to get our HEO with linear  
transponder, doesn't this spell significant interference problems for  
VO-52, Do-64, and other satellites which might carry linear  
transponders into LEO?

I'll thank you all in advance for your thoughtful comments...

	Mark



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