[amsat-bb] Ridge Test Results

Nathaniel S. Parsons nsp25 at cornell.edu
Mon Apr 21 20:06:42 PDT 2008

Hi again, everyone.

It's a little overwhelming to get so much help at once, but thank you,
everyone, for all of it.

One clarification: I did indeed mean pF, not uF for the capacitors in the
matching circuit.

Also, we performed another ridge test this evening (another typo there: the
ridge is 3.18km from the roof where we have the ground station setup), using
the complete ground station (minus pre-amp), and TH-D7 with rubber duck.

We transmitted from the ground station, while varying the amount of
attenuators between the TS-2000 and coax to the antenna. The "PWR" column is
in the format (TH-D7)/(TS-2000).  With each test, two 319-byte packets were
sent by the ground station in rapid succession. The results are below. If
any of this is not clear, I will do my best to clarify things.

Also, the entire test was performed at 437.405MHz, at 1200 baud, even though
we would like to operate at 9600. I have gotten 9600 baud to work when two
TH-D7's are across the room from each other, but since 9600 baud didn't work
during the initial configuration, we decided to just characterize the rubber
duck at 1200.

Ant. Pos.   PWR    Atten.   Packets
Vertical   .05W/5W  0dB       2/2
Vertical   .5W/5W   50dB      0/2
Vertical   .5W/5W   45dB      1/2
Vertical   .5W/5W   45dB      2/2
Vertical   .5W/5W   50dB      0/2

Horizontal .5/5     50dB      0/2
Horizontal .5/5     45dB      1/2
Horizontal .5/5     45dB      0/2
Horizontal .5/5     45dB      0/2
Horizontal .5/5     45dB      0/2
Horizontal .5/5     40dB      0/2
Horizontal .5/5     40dB      0/2
Horizontal .5/5     35dB      0/2
Horizontal .5/5     30dB      2/2
Horizontal .5/5     30dB      1/2
Horizontal .5/5     30dB      2/2

45 deg.    .5/5     30dB      2/2
45 deg.    .5/5     30dB      2/2
45 deg.    .5/5     35dB      2/2
45 deg.    .5/5     40dB      2/2
45 deg.    .5/5     45dB      1/2
45 deg.    .5/5     45dB      0/2

Comments? Concerns? Questions?

My initial interpretation of these data is that our square loop antenna has
a MUCH lower gain than is required, and something like a short length of
measuring tape would be a better substitute, as has been suggested by
numerous people.


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