Spring 2012 Progress Report
EE 482
Team Leader: Josh Beighle
Group Members: Adam Chen and Aaron Seyfried
Faculty Advisor: Dr. Wu
High Altitude Balloon – DDF
Final Design Specifications:
The Doppler Direction Finder (DDF) system gives the user an approximate bearing to the balloon as it is
in flight. Using a circular array of LEDs, the DDF displays the bearing in increments of 22.5 degrees. This
was not desired at first, but after speaking with Dr. Slater, the Mechanical Engineering team advisor, he
stated he would be ecstatic with 22.5 degree increments of direction to the balloon. This system will at
least give some general direction in which the balloon and package are traveling if the GPS system were
to fail. This way everybody that is foxhunting for the package has a more precise direction to the
balloon.
Design Implemented:
The design of our experiment is to use the bearing indicators from the DDF kits from stationary
locations to track its position during flight. Placing one DDF south of the anticipated path, and
one north, the relative position of the balloon can be tracked. The relative position of the
balloon will be recorded at time intervals to be specified at a later time. Using the bearing to
the balloon from each of the kits the ground track of the balloon can be determined. See Figure
1 for clarification.
Figure 1 – Planned Experiment
Detailed implementation progress:
All of the major parts of the project have been received and built, despite having to purchase a
third kit after the first kit was determined to be non-functional. Functional testing has proven
the feasibility of the project. During the first test of functionality, the CW beacon was not
functional and thus the testing was inconclusive. In the future, with the CW beacon operating,
the tests should prove valid.
Successes/Setbacks:
The team has had great success in the latter part of the senior design sequence. During this
time, we have found that one of the kits was not functioning properly and replaced it. The
overall time for kit construction was significantly faster than previous attempts. Furthermore,
the experiment was constructed and tested. The CW beacon was not functioning properly and
thus the kits received no input. This was a major disappointment in the field, until the team
realized there was a problem with the beacon and not the DDF kits. Later in the same week, the
team tested the feasibility of the project once more and gathered small-scale data. This data is
conclusive with the design approach.
Also, the original configuration of the Yagi antennas was deemed to be incorrect by engineering
advisors. The “y” connection at the driven element of the Yagi antenna was producing improper
impedance. To remedy this error, the coaxial cable was extended to connect directly to either
side of the driven element. This corrected the improper impedance match and the antennas
began functioning properly.
Supplemental Work
In keeping with the demands of the balloon team, our group has also designed and built
6 Yagi antennas for fox hunting purposes. The antennas were design to operate on the 70 cm
band. The bodies of the antennas were constructed using PVC pipe with the elements being
made of metal measuring tape. Of those antennas built, one was tested and yielded a Standing
Wave Ratio (SWR) of 1.12. The remaining antennas will be tuned to a similar SWR via
impedance matching. This is to be accomplished in a similar fashion as the one tuned antenna,
by adding or removing the wire bridge between the two halves of the driven element.
Schedule:
The schedule for the remainder of the quarter is displayed in the following table:
Event
Date
Poster Presentation
May 18, 2012
Launch 29
June 2, 2012
Final Presentation
June 8, 2012
The poster presentation will take place at the Russ Engineering Center, Wright State University,
on May 18th, 2012. This will include the presentation of a poster containing detailed aspects of
the team’s design, implementation and plans for Launch 29. The final launch of spring quarter
will take place on Saturday, June 2, 2012. This launch will be the implementation of the large
scale balloon tracking scheme developed using DDF kits. The final presentation for senior
design will be held on Friday, June 8, 2012.
Conclusion:
In conclusion, the overall project for both winter and spring 2012 has been conducted in a
timely manner. The team plans to collect data at the next balloon launch and verify their
experimental design at that point. The supplemental tasks, in support of the greater balloon
team, have gone very well. All members of the DDF team have attended at least two balloon
launches and have helped the mechanical engineering teams implement their tests. The
contribution of six Yagi antennas will also aid the greater balloon team and all teams to come.
At this point in the design, the DDF team is fully prepared to implement.
References:
Ramsey Electronics, LLC. "Radio Direction Finder Kit." 2011. MS DDF1. Victor, New York.