STRATOSPHERE ONLINE

Volume 2, Issue 3 --- August, 1992

Tim Kelliher, N0RHE, Hardcopy Editor

This is the electronic version of the Stratosphere Newsletter. Occasionally final editing is done to the actual layout of the newsletter and spelling checks, and other corrections may not make it into this edition. The content is complete (except for graphics).

CONTENTS

President's Corner

Congratulations EOSS, we are now 100+ members strong. The membership ranks of EOSS continue to grow and last month we went over the 100 mark. For an organization that is only a year and a half old, it is obvious that we must be doing something right. Welcome new members!

I'm happy to report that we have received the 501(c)(3) nonprofit, tax exempt status from the IRS thanks to the hard work of primarily Merle McCaslin. This was followed by the receipt of our Colorado certificate of exemption. All of this means that now contributions to EOSS are deductible. Expenses to support EOSS projects ar deductible. Purchases we make to support EOSS projects are exempt from state taxes. This status has already helped to collect some contributions and I hope more are out there.

There are a number of on going activities that will require more support. The development of the second generation Shuttle (our standard balloon bus) is now underway and will require both members' time and financial support. If you are interested in joining the Technical Committee and helping with this important effort, contact Dave Clingerman, W6OAL.

Tom Isenberg, as chairman on the Education Committee, is recruiting help for his committee's tasks. As education is one of our primary functions, I urge all of you to consider joining Tom in his fine work.

The continuing upgrade of our EOSS Ground Station is being headed up by Rich, N0PQX. His efforts will preclude the necessity of all of us tearing down our own stations each time to loan equipment for the ground station. If you know of spare or inexpensive equipment that might be integrated into the ground station, let Rich know. Specific items sought include:

  • Dumb terminals or computers
  • 2 meter and 70 cm transceivers
  • 12 volt power supplies
  • 2 meter and 70 cm Antennas (long boom)
  • Televisions and VCRs
  • 4 foot equipment rack

Well, that's it for this issue. Thanks again to Tim Kelliher, N0RHE, for the find job putting together "Stratosphere". I'll look for all of you at our next meeting!

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VOR Navigation Experiment

by Mike Manes, W5VSI

About a year ago, I dreamed up the VOR Navigation Experiment after looking over the DF bearing plots recorded during EOSS-2. What a rat's nest! It requires a lot of skill and teamwork to sort out truth from fiction given a set of even the most carefully determined VHF-DF bearings, as Ed and Paul will surely attest, and as I learned firsthand during EOSS-3. Multipath and strong reflections from the front range can really foul things up. With DF plots done every 10 minutes, you never know for sure where the balloon is right now. There just has to be a better way. Well,there are. The Global Positioning System (GPS), which uses a constellation of satellites, is exquisitely precise in three dimensions. Its use could make the "bushel basket" payload recovery notion near reality. GPS signal processing is quite complex, however, and commercial receivers eat about 3 watts of power and plenty of gas money. LORAN-C, which operates at 100 KHz, is more than accurate enough for terrestrial application, but its signal processing is still non-trivial, and its accuracy at high altitude is questionable.

The TACAN navigation aids which I relied upon back in my Navy flying days were accurate enough to take me practically down to the flight deck. TACAN is a bit hairy to process, but a bit of study revealed that the older and simpler VOR system promised +/- two degree bearing accuracy, which jived with my own experience. There are plenty of VOR stations around, so acquiring three of them for a triangular plot should be easy anywhere in the country. So, VOR was my choice for a first shot at on board balloon navigation.

As described in an earlier "Stratosphere" piece, the flight system developed for this experiment comprised a horizontally polarized omni antenna, Ramsey AR-1 112-118 MHz AM receiver, and a mux to link the receiver audio into the ATV audio channel. The AR-1 was modified to improve its image rejection (FM broadcast mainly), to widen its dynamic range, to incorporate synthesized tuning which could be programmed by the spacecraft processor, to slow down its AFC and lower its audio response to yield phase error free response at 30 Hz. In short, a gut shot.

The ground station comprised an ATV antenna and downconverter, 7" TV set, modified to bring out a dc-20KHz audio signal, an external AF amplifier/buffer and a Narco VOA9 VOR decoder/display donated by Denver Avionics. The system was ground tested from a few sites here in the Denver area using the VOR station at Stapleton, DEN on 117.0 MHz. Surface VOR signals are quite weak and subject to multipath errors, especially from the multitude of aircraft operating around Denver. But from the few usable signals I heard, from Green Mountain and Highlands Ranch, I felt that a 5 degree bearing accuracy would be achievable.

Although there were some offers to flight test the system, a realistic test would have to be done with a fully configured payload to resolve questions regarding known EMI from the payload, would require a ground station to listen to the ATV, and VOR and ATV antennas would have to be mounted on the aircraft. The flight duration would be too short to allow on-line correction of any detected flaws, and repeating such a test a few times would no doubt stretch other peoples' patience. For 25 mA of power and 3 oz. of weight, a regular EOSS launch was judged to serve this purpose.

The system first flew on EOSS-5. I set up in the field at the I-70, Colorado Highway 86 interchange, close to the expected flight midpoint. I used an 11 element yagi and downconverter with no preamp. Although ATV was acquired only 3 minutes after launch, the best signal over the entire flight was quite snowy, and there was a lot of white noise and buzz in the audio. The decoded bearings were unstable and obviously incorrect. My dismay was abated only by the fact that I was out of range of the field repeater and could defer reporting those awful results.

The planned fix was to receive the best possible ATV signal to eliminate that probably source of error. So on EOSS-6 (Humble II), I set up at the launch site and tied into the downconverted output from Jack's huge az-el Yagi and LNA. Starting moments after launch, the video was flawless, and the VOR audio was cleaner than any I had heard to date. But the 30 Hz audio was badly distorted as monitored on an oscilloscope, and the bearings were still obviously wrong! They seemed to be changing in the right direction and at the right rate, however, so I suspected that there might be some fixed offset which I could subtract out. A solid 90 degree error could be caused by loss of one of the audio components, so I tried that first. It appears to work reasonably only on the DEN signal. Kiowa IOC seemed more like 180 degrees out, though and Gill (GLL) was somewhere in between. Several "corrected" DEN bearings were issued to Paul, but in the end, they rated dead last in correlation with the other field station reports. If there's any consolation on this flight, it's that the VOR wouldn't have helped pinpoint that flight's landing site even if it had worked flawlessly.

The problems which caused the errors have not been nailed down, but there is no lack of suspects:

  • Receiver front-end overload
  • EMI from the processor
  • Intermod from the 2m signal
  • Distortion in the ATV audio link
  • And ... plain old broken wires

There is, however, a shortage of zeal necessary to nail the culprits down and fix them. At this point, I think the VOR experiment has consumed its share of He and Li. This doesn't mean that we shouldn't pursue on-board navigation, though. Whatever approach we take should exploit what I think has been learned from this work:

  1. Keep the nav signals clean and well clear of on-board sources of interference. VHF AM is not advised.
  2. Don't depend upon the ATV baseband audio link for high quality analog telemetry. It's fine for voice grade work only.
  3. Navigation signals should be reduced to digital form on board for downlink on packet.
  4. Design the system so that it can be easily flight tested, and get commitments, if you are so audacious, necessary to conduct the test plan before tying up a lot of time developing it.
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Congratulations RMRL

EOSS wishes to congratulate the Rocky Mountain Radio League (RMRL) on their successful balloon flight of July 18th. The balloon payload consisted of a cross band repeater with an input of 446.000 MHz and an output of 147.555 MHz. Repeater contacts included those from Kansas, Oklahoma, New Mexico, Wyoming and of course, throughout Colorado.

It was a special treat for several of the fox hunters to actually visually track (with the unaided eye) the balloon as it neared its maximum altitude. Then, "poof", it was gone as the balloon exploded and the payload started its descent. Clear skies, a perfect Sun angle, and the 30 foot diameter of the balloon at max altitude all contributed to this rare treat.

It was interesting to note that alkaline batteries were used in this flight. This is further proof if you keep things warm, a lot of compromises can be made. Bob Ragain, WB4ETT, did the excellent packaging job that both protected the payload and kept the cold out.

Warren Gretz, N0FVG, did an outstanding job conducting an orderly net on the repeater and Glenn, WN0EHE, was the payload integrator. Greg, K0ELM and his team of fox hunters did their usual outstanding job in the lost and found department, recovering the payload in about 20 minutes after touchdown!

Once again, congratulations RMRL on your project. It was great fun!

(EOSS assisted in the RMRL project with the procurement of the balloon and helium, the loan of a parachute and 10 meter beacon, balloon inflation and launch operations. Many EOSS members assisted in the tracking and recovery operations as well. EOSS will gladly assist other groups in similar projects.)

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From the Desk of the EOSS Chief Scientist

I'd like everyone who participated in the latest EOSS balloon launch to know that their efforts are definitely appreciated by me and I'm sure the membership at large. The team effort was gratifying from design, development, integration, check out, launch, tracking and recovery personnel to those that merely helped keep the dogs from playing in the middle of the balloon. I felt a little bad about the FAA calling our effort a "derelict." They might have been so kind as to refer to it as a "rogue", but derelict is a little strong.

Well anyway, onward and upward, we have things to do. Lots of people and associations would like for us to take their systems and experiments to the "edge of space." Let's go for it!

We have about a 20 person Technical Committee that encompasses an abundance of talent and we will use every bit of it in our future endeavors.

A project I'd like to see come to fruition is a portable weather station that can be erected at the launch site. My interest in having such an enhancement is illustrated on Humble I and Humble II launch days. At both launches the wind direction at 0900 or 0930 did not coincide with the runway layout of 0700. I know there are students within the membership of EOSS that have meteorological experience on which we'd like to capitalize and in the process train others on how to use meteorological equipment. Also, it is sometimes rather difficult to have everyone of the Technical Committee get their hands into the spacecraft shuttle or payload. This would be another opportunity to allow students to acquire other "hands-on" experience in the design and construction of electronic and scientific equipment. Much of our charter in the creation of what is now EOSS was the nope that we not only might get more people thinking about scientific careers but be able to function as more than a theoretician in those careers. Many times throughout my career in electronics I have had to deal with the young engineer who had all the credentials and could tell me all about a transistor, right down to the sub-atomic structure of the silicon but yet couldn't solder one into a circuit board.

Many of us don't know what we want to e when we grow up and there is always going to be a need for meteorologists. Maybe we can help, with this proposal, some people to find their niche. Now, I don't propose we go out and buy a Heathkit weather station. What I am proposing though, is the "home brewing" of this station from our junk box treasures. The anemometer can be constructed from the plastic egg shaped containers in which Leggs Panty hose are packaged. The generator can be constructed from a small brushless electric motor or build from scratch. The wind direction can be sensed with a vane of balsa wood and attached to a small synchro transmitter. Wind speed and direction can then be input to a "home brew" chart recorder. Today, we can probably make better ones than some I have had to use in the past. Dry and wet bulb temperatures can be sensed physically and the information sent electronically in an analog or digital form to recording devices. If the running of wires between sensors and recording devices seems rather passe, let's try our hand at fiber optics. There is really no great hurry in completing such a project an it could be done in stages - built, tested and refined. Who knows what clever ways of acquiring and presenting data with which we might come up. We might even hit on something in which the National Weather Service might be interested.

I further propose that the sensory devices be made light enough to be raised on a small balloon to a height of 100 or so feet giving us an indication of other than surface activity. Just some thoughts - remember we are only limited by our own imagination. Don't be afraid to dream!

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Field Day Tethered Balloon-Antenna

During Field Day weekend in late July, EOSS provided the Waterton Amateur Radio Society (WARS) a tethered balloon antenna system that accounted for over 500 Field Day contacts.

EOSS members Merle McCaslin, Tim Kelliher, Dave Clingerman, Mike Manes and Jack Crabtree arrived at the WARS Field Day sit at 9:30 am and soon, the five-eights wavelength, 160 meter vertical antenna (300 feet long) was being supported by an Edmund Scientific balloon inflated with helium to a 6 foot diameter. Three nylon cord guys were used to help stabilize the movement of the balloon system in the wind. Later, a second but smaller balloon was attached to help support the antenna wire. The antenna was fed with open (ladder) feed line with a tuner to allow multi-band operation.

That afternoon, as a storm passed overhead, winds kicked up to at least 30 MPH. The resulting stress on the larger balloon caused it to burst. Quick thinking saved the day. The guy cords were discarded and the antenna length was shortened to a quarter wavelength at 160 meters or about 135 feet long. The smaller pilot balloon easily supported the reduced weight antenna. Field Day contacts were only briefly interrupted during the adjustments.

The balloon-antenna system stayed aloft throughout the night. At dawn, it was noted that about 10 feet of the antennas was periodically scraping the ground in the light breeze. Perhaps the combination of the cool air and some leakage of helium from the balloon was causing the balloon to lose some of its lift capacity. Another antenna length adjustment was made, this time to 65 feet or quarter wavelength at 80 meters. Contacts again resumed.

All in all, some 500+ contacts were made using the balloon system. Most were made on 20 meters followed by 40 and 15 meters. EOSS gained some additional knowledge and experience in using balloon-borne antenna systems while demonstrating how balloons might be used in an actual emergency situation.

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Ground Reflection

Thanks this newsletter go to two guys that have helped EOSS and have been generous with their time and property. First thanks to Rich Volp, N0PQX, an EOSS member and Heritage Student who took over and did a great job with the ground station for EOSS-5. Also, public thanks are due to Bud, owner of Electronic Bits and Pieces (Colfax and Iola, in Aurora). Bud has been very generous with miscellaneous parts, as well as his contribution of the LORAN-C equipment. We will be designing a project to try to improve the TV downlink and will announce our plans on an upcoming net. Rich and I have a lot to learn about ATV and will be counting on help from some of you experienced ATV operators. Thanks in advance!

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Education Notebook

Entering into Education Chair at the first of 1992 was view by me as a position that could slowly nurture an education plan by integrating personnel and projects. In ernest effort to tackle what was perceived as a hard chore, we contacted a few schools to give our pitch and hope for success. Along the way, many other education groups were contacting EOSS concerning our educational opportunities. I have to give all EOSS members an "A" for the great public relations they did in securing all the interest. Suddenly I found myself in a swarm of bees and now all bets are off with any plans I initially started. To put the education plan back in order I need help. The EOSS membership has expressed interest in education, however, I've been slow to respond. My dedication to an education plan has not diminished, but I also want the membership's input as to what plan we want to put in place and utilize the membership in the execution of that plan. If we carefully assign tasks, the labor will not fall on a few.

All who have expressed interest in being a part of the education team please plan to attend the first education meeting on Thursday, August 6, 1992.

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A Minute with the Secretary

There have been three general meetings since the last newsletter. Obviously not all 100+ members can be expected to attend every meeting. This column of the newsletter is intended to provide a brief synopsis of the general meetings (committee meetings will not be included) for those who were unable to attend a particular meeting.

May:

  • Treasurer's Report $1063.47 banked
  • Motions
    • File Tax forms ASAP - PASSED
    • New Secretary Tim Kelliher - PASSED
    • Buy pre-amp for ground station - PASSED
  • Discussed
    • Colorado Springs hamfest
    • payload drop contest
    • Humble II logistics
    • proposed next flights (State Fair, GPS, RMRL)
  • Treasurer's Report $868.21 banked
  • Motions:
    • Change by-laws to separate officers from the board of directors. PASSED
  • Discussed:
    • IRS Tax exempt approved
    • Humble II in review
    • Waterton tethered balloon
    • Colorado State Fair Launch
    • Video for State Fair
  • Tech Committee questionnaires passed out
  • Treasurer's Report 819.78 banked
  • Motions:
    • none
  • Discussed:
    • RMRL Logistics
    • Waterton Tether in Review
    • Tech Committee report on Tasks
    • Colorado State Fair Logistics.
  • RMRL donated a new tracking beacon, and again we graciously thank them.

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Cooperative EOSS Balloon Tracking with a Mac

When Tim asked for an article on "... how my program works," I gasped. I had just submitted a 5400 word article to "QST" that attempted to do just that. It would have been easier to say "wait ten months or so, and it will be in QST." (Instead I could build the battery charger I desperately need). However, after the QST "thesis" was completed, I learned that ARRL favors neither RDF articles, nor long technical articles. So I am at bat with two strikes while ARRL decides the fate of the article.

EOSS is, no doubt, sensitive to "Stratosphere" postage, and ARRL is sensitive about multiple submissions to publishers. Therefore, I will outline some of the Macintosh balloon tracking system that was used to aid the top-notch EOSS RDF team.

The routine runs on any Apple Macintosh computer capable of running Microsoft Excel 3.0, a spreadsheet application. There are two macros. (Microsoft claims it will also run on Windows series PCs).

The first macro does augmented triangulation in four automated parts:

  1. Triangulation
  2. Position Estimation
  3. Plotting
  4. Station performance monitoring

In the position estimating part, a double average calculation is performed to find the "hottest" point; distant points are ignored.

In the plotting part, an Excel Scatter Chart is used to show relative positions of the hunters, residual triangulated points, and the estimated position of the transmitter.

In the station performance monitoring part, a record is kept of the number of times a station's bearing was ignored because of divergence, or for producing a triangulated point deemed to distant from the centroid of all triangulated points.

The second macro saves all results and calculates balloon speed and heading for each sample time.

note: the original article contained an example session with graphs as figures. That information is not included here for brevity. See QST, July, 1993 for the article (and graphs) mentioned in this piece.

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Editorial

This will be my second newsletter as editor. I hope that all of you like the new look. Everyone warned me that getting articles for a newsletter out of a bunch of techies would be like pulling teeth. After the first issue I thought everyone might be right. As you can see from this issue, it may not be all true. I think that I may have found the secret to pulling those teeth. Make a deadline two weeks before you want to publish and just keep moving it back to satisfy the writers. Just kidding, I really appreciate all the support I have gotten from everyone. It has made my job a lot easier.

While this may be the EOSS newsletter, everything in it does not have to concern EOSS business. If anyone has anything they would like to see in the future, a new column, classified section or any suggestion please let me know.

Once again I would like to thank everyone who contributed to the newsletter and special thanks to Dina and Norm for helping with the hardest part of all, folding, stapling and stamping!

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