Thank you for careful review on this topic. I sincerely respect your
Bdale Garbee <[EMAIL PROTECTED]> writes:
> [EMAIL PROTECTED] (Glenn LeBrasseur) writes:
>> Unfortunately no part of 802.11a is in the amateur spacecraft
>> range. This kind of makes sense with regard to interference, since it
>> would be so easy for a spacecraft to interfere with a large number of
>> terrestrial 802.11a stations.
> The reverse is *far* more important, at least to me. ;-)
> A large body of unlicensed terrestrial transmitters bringing up the noise
> floor could make it *very* hard to hear amateur satellite downlinks, which
> are typically far too weak to cause any significant interference to
> terrestrial stations. In theory an uplink could cause interference to
> 802.11a stations, but since highly directional antennas are typically used
> aimed at the satellite, any real interference caused by an uplink is likely
> to be rare.
Yes, you are correct. I had my perspectives inadvertently biased toward
the terrestrial. I understand and agree with the problems with noise
pollution of extraterrestrial RF and light, and am an advocate to their
>> Power levels
>> are limited to the license class , which for the technician class
>> is 200 watts, and the overall power limit stated in CFR 47-97.313(a)
>> and (b).
> I think you mis-read that part of the rules. The actual power limit for all
> licensed amateurs on that band should be 1.5kW PEP. However, the restriction
> in the preceeding section on spread-spectrum transmissions likely applies, so
> the limit may be 100W. In practice, these distinctions are not important,
> because making gobs of power on C band requires *serious* heroics. A watt is
> pretty easy, a few watts is plausible, serious uplinks for things like EME
> typically involve TWT amplifiers, mongo amounts of heat sink mass, and/or
> cooling... you *really* don't want or need lots of watts for this task.
Mis-read is too polite; I simply overlooked 802.11a is spread-spectrum
(SS), which is a new privilege. However as you point out, we will mostly
be dealing with power levels on a practical level that is well below any
power limits of the law. I expect we will be able to work 1 to 3 watts
into an antenna with maybe 0bB of gain, hopefully. We'll see.
>> The way I see it, using 802.11a will work for us up at larger amateur
>> power levels until we actually get into space, and either need the
>> higher power levels (more than 3 watts say) for the link budget, or
>> our footprint increases and we actually become a spacecraft.
> When you become a spacecraft, you'll want/need to coordinate use of
> in the amateur satellite sub-bands. As long as you're on something like a
> ballistic trajectory, the should continue to apply.
It is reasuring to confirm that you believe a ballistic trajectory
follows terrestrial rules. We will probably be there for a while.
However I expect we (PSAS) need to be thinking about the space segment
sometime soon. How do you think we should proceed?
> 73 - Bdale, KB0G
Bdale, Thank you sincerely for your critique.
73 - Glenn, KJ7SU
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