[amsat-bb] Re: AO-51 short experiment

Larry Gerhardstein W7IN at montana.com
Sun Oct 24 14:00:59 PDT 2010

No one 'owns the frequency' and if in-place coordination can not resolve 
the issue, the newest user should consider moving out of the required 
bandpass.  Was the first user ever coordinated?  ~~Larry W7IN~~

On 10/24/2010 2:45 PM, Alan P. Biddle wrote:
> Bob,
> 145.825 is the "established" space APRS frequency, and has been/is used by
> more than just the ISS for years.  There are other APRS satellites which are
> intermittently active on the same frequency, and I expect there will be
> others in the future.  I can't address the formal coordination issue, but
> anything with an uplink on that frequency is guaranteed to have problems.
> The only question is whether those problems are tolerable.  There is little
> to no APRS activity on that frequency over most of the world, and then there
> is the question of both HO-68 and the ISS being in the same footprint.  The
> HO-68 has an inclination of about 102 degrees, the ISS about half that.
> Finally, the ISS is not active on that frequency 24/7.  It operates on other
> frequencies for voice and SSTV, and is often QRT completely due to other
> operations.  In an imperfect world, it looks like a reasonable tradeoff,
> though other evaluations are certainly possible.
> The problem of unattended APRS beacons does cut both ways.  There are some
> daylight-only APRS satellites.  When they enter periods of extended
> illumination, they can be commanded from their default modes.  However, even
> a single "braaap" can pull the DC busses low enough that the command
> stations need to start over again.  WB4APR has lamented this problem, with
> specific calls, in other venues.  Looking at some of the paths, both in
> Drew's example and my reception, there are stations whose paths have not
> been updated for years.
> The sort of courtesy/coordination issue is not limited to space operations.
> A ham relatively local to me fired up a propagation beacon on 30 meters this
> month.  It is/was within 200 HZ of an APRS frequency which has been in use
> for some time.  Quite a fight over who "owns" the frequency.  ;)
> Alan
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