[amsat-bb] Possible ISS School Contact Experiment idea? (Thurs)

Robert Bruninga bruninga at usna.edu
Tue Oct 20 22:05:57 UTC 2015

> An ISS school contact… in Michigan on 22 Oct.
> … to begin at approximately 17:14 UTC.

This is a great time for those skilled portable "arrow" operators to get
data on using fixed vertical arrow beam antennas for ISS voice at or near
the horizon.

The test will show if well placed fixed tripod "arrow class" antennas at AOS
and LOS and a central turnstyle could possibly make it easier than a full
AZ/EL Oscar class antenna at the school.

Testers, Please read the concept paper at http://aprs.org/aos-los-test.html

If your QTH is west of Michigan, then you should test your LOS horizon.  If
your QTH is east of Michigan, then you should test your AOS horizon.  This
is because we want to make sure we are getting voice quality data AT the
horizon while the ISS crew is actually speaking.

The desired data is a minute-by-minute log throughout the pass of ISS signal
quality (noting nulls or fades) without moving or adjusting the antenna.
Your receiver must be right near the antenna (no coax loss).  Just orient
the beam vertically with an up tilt of 15 degrees.  Then aim it at a fixed
Azimuth that is half way between AOS (or LOS) and when the ISS rises above
(or drops below) 30 degrees elevation to cover the first (or last) portions
of the pass.

Leave your antenna fixed throughout the pass.  We need to know how well the
squelch on your radio eliminates the weak signal when the ISS is outside
your particular fixed beam too.

In a real scenario of this full technique, above 30 degrees the ISS is 3
times closer and 10 dB stronger and would be heard fine on a central omni
antenna.  But that is not part of your horizon performance test.  So be sure
to choose a good low horizon *and* the horizon you share with the School
contact in Michigan so that there is ISS audio during your particular
horizon crossing (AOS or LOS).

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..

If this concept works, then the idea would be 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.  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 you are in range of this Michigan ISS school contact, and you have an
arrow on a tripod at your QTH, you could collect data on a horizon
transition to see if this idea is a possibility.

Again, YOU ARE RECEIVE ONLY.  Your test is *independent* of the actual
school contact, you are just taking your own receive data wherever you are
of how well a FIXED 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

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
crossband-repeating mobile rigs and three UHF HT's could be made into a
suitcase GOKIT to standardize some school contacts with a lot less work.

Just an idea
US Naval Academy

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