[amsat-bb] Possible ISS School Contact Experiment idea?
bruninga at usna.edu
Mon Oct 19 02:10:14 UTC 2015
I wonder if we could collect data from skilled portable "arrow" operators
on the reception of ISS comms near the horizon during upcoming school
The interesting question is the viability of using well placed fixed tripod
"arrow class" antennas at AOS and LOS instead of the current requirement
for a full AZ/EL Oscar class antenna system at the school. By using two
fixed portable beams on the AOS and LOS sides of the school for reception,
for example, then maybe the 50W uplink can work fine from a more simply
located and operated central omni antenna that is easier to set up.
A concept paper with details on this idea will be posted Monday afternoon at
The desired data would be a minute-by-minute log throughout the pass of ISS
signal quality especially noting any nulls or fades without moving or
adjusting the antenna. Just orient the beam vertically with an up tilt of
15 degrees. Then aim it in Azimuth half way between AOS (LOS) and when it
rises above (drops below) 30 degrees elevation to cover the first (or last)
portions of the pass. Above 30 degrees the ISS is 3 times closer and 10 dB
stronger and would probably be heard fine on the central omni.
An audio recording would make it easier to prepare the log after the pass
or you can just make checks or X's every 5 seconds on a piece of paper and
summarize it later. Do NOT run open squelch. Set the squelch for normal
ham radio operation to silence the radio when the signal would be
unintelligible anyway, since we would not want unintelligible noise from
one receiver to distract from good audio from the possible others..
The concept is to bring in all three receiver speakers (left-to-right) into
the auditorium operating position to give equal weight to each receiver but
also give a sense of the passage of the ISS. During this test, It is
tempting to want to re-orient or move your AOS (or LOS) beam, but we need
the data horizon to horizon on the original fixed antenna orientation to
see how well the squelch eliminates the distraction of a noisy receiver
when it is not the prime contributor.
If this test shows any promise, it could not only eliminate all the
complexities of long crossed yagis, AZ/EL rotators, big masts and active
tracking, but also completely eliminate the problem of long runs of coax
from the school gymnasium to the antennas. The coax is eliminated by
placing 50W mobile rigs (capable of cross band repeat) at each of the
possible three antennas and operating them remotely via 3 UHF HT's indoors
on-stage (coupled into the sound system).
So, if there will be an ISS school contact within range of your station,
and you have an arrow on a tripod at your QTH, you could collect data to
see if this idea is a possibility. Again, this is *independent* of the
actual school contact, you are just taking your own receive data where ever
you are of how well an arrow on a tripod can hear the ISS at low
elevations. Be sure to find a place with a good horizon at AOS(or LOS) to
set your antenna.
I'm on deadline to deliver a satellite in 12 days, and so if someone else
might be interested in collecting and summarizing any incoming reports,
that would be helpful too.
If we learn that there will be any significant fades or loss of signal,
then this idea fails... But if it works, then the two arrows, tripods,
three mobile rigs and three UHF HT's could be made into a suitcase GOKIT to
standardize school contacts with a lot less work.
Just an idea
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