W6SDO.COM SAN DIEGO, CALIFORNIA USA
THE ORIGINAL PROOF OF CONCEPT KITE-ANTENNAS - THE SHORT STORY
THE BASELINE ANTENNA DESIGN AND TEST PARAMETERS:
The 20 meter band has been select for this kite-antenna project because both North American and world-wide contacts
can be made on this band during the daytime hours. This is also the most likely time when the winds will be strong
throughout the San Diego coastal zone where we live.
The antennas will be flown as high as possible above the ground to assure the best efficiency and the most favorable
radiation characteristics. These antennas will be fed from the ground using a suitable length of RG-8x light- weight
coaxial cable. Each kite-antenna design will be capable of supporting power levels up to 500 watts.
Both horizontal and vertical dipole antennas will be evaluated. It is expected that a horizontally polarized dipole should
be a better antenna for covering North America while a vertical dipole, with a much lower radiation angle, should have
the edge for contacting DX stations.
A sturdy 12 foot ITW Rivera Highlander delta kite will be used to lift this first series of kite-antennas. This kite can easily
lift 4 to 5 pounds of combined antenna and cable weight to heights well over 80 feet in a moderate 8 to 12 MPH wind.
TESTING THE HORIZONTAL DIPOLE KITE-ANTENNA:
For this test, the wires that make up the two halves of the horizontal dipole were temporarily attached around the
perimeter of the delta kite using nylon tie-wraps. The “left over” dipole wire length was then allowed to drop off the two
rear delta kite corners where they will trails behind and below the kite in flight. Modeling of this antenna configuration
predicts slightly less forward gain but shows much higher signal strength off the ends of the dipole, where there would
otherwise be sharp nulls. This pattern is ideal for our San Diego location since our usual Westerly winds will direct our
strongest kite-antenna generated signal strength over the largest porting of North America.
The dipole center point is fed through a 1:1 balun in order to interfaces the balanced dipole with the unbalanced RG-8x
coaxial cable feed line. A carbon fiber rod has been added along the bottom of the kite’s keel so that the weight of the
balun and coaxial cable can be suspended from the optimum point along the length of the keel. This adjustability allows
the kite to deliver its best lifting and stall recovery performance. Finally, the antenna was tuned so that it resonates at
14.245 MHz when the kite is flown at 80 feet. It was observed during testing that the resonant frequency of this kite-
antenna does not change significantly for flying height ranging from 30 feet to well over 100 feet.
The first test flight of this kite-antenna was conducted April 16, 2016. For this first test the kite-antenna was powered by
W6SDO’s 100 watt bicycle mobile transceiver. A total of 23 contacts were made which included nine states and two
Canadian provinces. The results of this first kite-antenna flight were reported in an article published in the AMERICAN
KITING ASSOCIATION’S FALL 2016 issue of KITING magazine.
The second test flight of this kite-antenna was made May 29, 2016. This second test flight provided us with a total of
over 60 contacts for the two test sessions. In all cases our signal reports were very good and closely matched results
from the first test flight.
TESTING THE VERTICAL DIPOLE KITE-ANTENNA:
For this kite-antenna test, which was conducted on November 19, 2016, a half wave center fed vertical antenna was
hung below the kite. A 5 foot length of ¼ inch bungee cord between the end of the antenna and the kite provided
some “softness” to the kite’s pull on the antenna. The upper section of the vertical dipole uses a flexible 14 gauge
antenna wire so that it can support the weight of the balun, lower dipole leg and the RG-8x cable that feds the
antenna. The lower dipole leg is made of 20 gauge stranded hookup wire, and was suspended from one of the two
balun terminals. In flight, the lower leg of the dipole is typically pulled two feet or so away (downwind) from the RG-8x
cable by a 6 foot long kite tail attached to the end of the wire. Ferrite cores, “snapped” around the RG-8x cable at a
point a half wave below the balun, keep the nearby section of the coaxial feedline cable from developing significant
coupling to the lower dipole leg.
As with the horizontal dipole test, this antenna test was powered with 100 watts and the high point of the vertical dipole
was flown at around 80 feet. For this vertical dipole test 37 stateside contacts were made. In addition, we also made
three very solid “long distance” contacts which included Guatemala, Novi Scotia and Hawaii. This seems to confirm the
vertical dipole’s superior DX capability. In the future, we are planning to do a more accurate horizontal versus vertical
comparison when we will have both antenna configurations in the air at the same time and at similar height.
SOME IMPORTANT KITE-ANTENNA IMPROVEMENTS THAT HAVE BEEN RECENTLY MADE:
The carbon fiber rod along the keel of the kite has been removed and replaced with nylon loops sewn to the kite’s keel
at the appropriate load lifting locations. This reduced the kite’s weight by about 14 ounces.
A custom balun has been designed and fabricated that adds only 3 ounces to the weight that the kite must lift. This
design improvement provides a weight saving of about 11 ounces without sacrificing balun performance.
The horizontal dipole wires have now been threaded inside of the kite’s “seams” and the wires now remain permanently
attached to the kite. This allows quick and easy deployment of either the horizontal or vertical kite-antenna
configuration in 15 minutes or less.
Both of these kite-antenna configurations can easily accommodate up to 500 watts.
The antenna weight reductions allow these kite-antennas to fly at much lower wind levels.
Either of these two kite-antennas can be deployed in 15 minutes or less.
The kite-antenna that we will choose to fly on a given occasion will depend on whether we want to work
mostly stateside stations or try for some DX contacts.
Flying both the horizontal dipole and the vertical dipole kites at the same time, using an A-B switch
connected to the two coaxial feed lines to select either the horizontal dipole or the vertical dipole, should
provide some very interesting signal “diversity” results.
The vertical kite-antenna will also be flown soon using a large Rokkaku kite in preparation for the
International Marconi Day event in April 2017.
Bob (W6SDO) and Mert (AF6HF) making a few kite-antenna contacts ITW Rivera Highlander delta kite fitted with a 20 meter horizontal dipole antenna