[amsat-bb] Re: Frequency Co-ordination.
kf6kyi at gmail.com
Mon Jun 16 10:10:15 PDT 2008
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
145.945 (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...
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