A Sky-Eye for Field Dayby John L. Gafford, N5XAK
Recently the club was brainstorming ideas for the annual ARRL field day which is always the last weekend in June. What came out of the "storm" was a self-contained TV camera and transmitter carried aloft with helium-filled weather balloons.
WATS "SKY-EYE" is the result. It consists of a PC Electronics TXA5-70 ATV Transmitter board, an Intuitive Circuits OSD-ID (SA) stand-alone ID board to provide station ID as required by FCC regulations and an ATV Research BC-CMOS300 color camera module all packaged it a PC Electronics CAB234 aluminum box. A quarter wave dipole antenna is mounted to the box using BNC connectors. Dimensions of the dipole antenna were taken from the TXA5 data sheet. The system is powered by eight AA alkaline batteries in a Radio Shack battery holder strapped to the bottom of the aluminum box.. RF output of the TXA5-70 at 12 volts is about 80 milliwatts. Operating frequency is 439.250 MHz. The entire package with batteries weighs about 23 ounces.
The TXA5-70 board was mounted in the bottom of the enclosure. A shield consisting of a sheet of cardboard covered on one side with aluminum foil was placed on top of the TXA5-70 board with 1/4 inch standoffs between the boards. The OSD-ID board was then placed on top of the shield. The camera was mounted in the end of the box with a carefully made hole resulting in a friction fit of the camera. The antenna connection was made with a BNC socket mounted in the side of the box. The quarter-wave dipole antenna was constructed on a BNC plug.
The OSD-ID board is programmed by manipulating four push buttons on the board. Any of 128 characters can be placed any where on the display in a text area of 28 columns by 11 rows. The display was programmed to show "WATS SKY-EYE KC5OYN" on the top line, and "ARRL Field Day June 26 1999" on the bottom line. KC5OYN is the Club call sign for WATS. This display is superimposed on the video signal provided by the camera.
Lift was to be provided by four three-foot weather balloons filled with helium. Each balloon is capable of lifting about 9 ounces in addition to its own weight, so we had a net lifting power of about 13 ounces for camera mount and tethers.
We had anticipated a trial run prior to field day using a large kite, but on the day of the test, sufficient wind to make a trial run was not available, so it all came down to a cold run on June 26th.
On Friday, June 25th a tank of helium was obtained, and early the next day we started filling the four balloons. As frequently happens, Murphy struck with a vengeance. While attaching the balloons to the support rod, the wind whipped the balloons around and impinged them on the camera antenna. Almost instantaneously we lost three of the four balloons.
Revert to Plan "B". The kite was brought out, and several successful flights were made with the camera attached to the kite. Also, several "crash landings" occurred, prompting the comment "John, you have just answered the question everyone has been asking, why did you use an aluminum box for a camera housing". The camera survived all the brutal treatment without any damage.
The kite, though providing more than sufficient lift for the camera package, was anything but ideal as a camera platform. There was much radical and random motion, making any images almost useless from a surveillance standpoint. But we did learn what not to do. Any subsequent attempts to use a balloon will use one six-foot balloon with sufficient spacing of components to preclude the disaster we suffered trying to use four balloons.
The photographs below cover construction of the camera, and some pics of trying to use the rig on the kite.
Left: The assembled skyeye attached to the balloons
Middle: The disasembled skyeye, minus the OSD-ID board
Right: The assembled skyeye, with the OSD-ID board on top and camera visible on the right side
Left: From left to right: Larry Bush W5NCD, John Chamberlain AC5CV - holding the SkyEye, Horace Bushnell W5TAH, Marshall Mabry KD5IQ
Right: From left to right: Justin Martin KC5KQL, Marshall Mabry KD5IQ, John Chamberlain AC5CV, Bill Cox W5JRM, John Lewis W5KKD