100 Ft Balloon Antenna
40M & 20M Balloon Vertical Antennas
Our radio club yearly public event has experienced low signal strength and poor signal reports. We needed a better antenna plan to make our event successful.
• Better performing antenna(s) are needed that can be setup on the town square
• Supports are limited to a few trees and lamp posts
• Tiedowns are limited by concrete and trip hazard concerns
• Counterpoise limited to flowers beds at band stand, everything is concrete and bricks
Antenna Best DX performance is objective
• Maximum radiation at 0 to 15 Degrees Elevation
• Bands are not used at the same time CW & PSK antennas can be swapped
• Antennas can be tuned to Tx Frequency
• Single band solutions for 40M and 20M
• Allows optimum performance without compromises
• Operate mainly a 40M and 20M operation
• Past has been SSB & CW event (desire to add PSK)
• Use Band Plan to help QRM
• 200 KHz between SSB & CW address QRM
• CW & PSK too close on 20M & 40M…
• Solution CW & PSK not in same band at same time
Operations
• Two SSB RIGS
- 14.266 MHz Balloon Antenna #1
- 7.255 MHz Cushcraft R7 Antenna
• CW RIG
- Primary 7.033 MHz Balloon Antenna #2
- Secondary 14.066 MHz Balloon Antenna #3
• PSK RIG
- Primary 14.072 MHz Balloon Antenna #3
- Secondary 7.036 MHz Balloon Antenna #2
• VHF/UHF RIG(s) Not addressed in this report
Frequencies
• Club owns Cushcraft R7 Antenna (7.255 MHz )
• Need to build three tuned antennas for SE
• Antenna #1 tuned to 14.266 MHz
• Antenna #2 tuned to 7.035 MHz
• Antenna #3 tuned to 14.069 MHz
Design
• Obtain best radiation in 0 to 15 Degrees elevation for greatest range / hops.
1. Vertical Dipole
2. 5/8 Monopole
3. 3/4 Monopole
4. 1/4 Monopole
Elevation Plot of Omni-Antennas Considered in Design
Testing
• Select Wire, Balloons and Helium
• Select insulator & leader
• Balloon lift tests with real wire
• Balloon lift vs. time tests need ~8 Hours
• Several overnight fatigue test of balloon, wire and insulator (try normal and windy)
• Test 3/4 WL vs. reference dipole on 40M
Lift
• Determined a 9 Inch Balloon = 50 Ft #28 AWG
• Three 12 Inch balloons = 100 Ft coil lift with margin
- Line is tight and secure by weight
- 12 Inch balloon = 12 X 19 Inches
• Latex balloons lift for less than 12 hours
• Lift is 2/3 original capacity after 8 Hours
• Lift is 1/10 original capacity after 24 Hours
• Decided to exceed equilibrium by 50% = Three 12 Inch balloons!
Wire
• Messenger vs. weight - Must fly to work
- #28 AWG Copper tensile strength ~ 22 LBS
- 12 Inch dental floss leader for fatigue (twisting)
• Insulator
- 30 LB Monofilament X 5 Ft
- Measured greater than 10 Meg-Ohms
40 Meter
3/4 Wavelength Details
• ¾ WL Vertical 40M Wire (7.035 MHz) into a 100 Ft Vertical nominal 55 Ohms assume ground rod at gazebo
• Mast required for safety (wind vs. people/structures) Do not worry about wind drift angle vs. RF
• Use true Current BALUN on ¾ WL (BAL on Ant end)
• RG-58 OK as 0.5 dB not noticed with +20 dB
40 Meter 3/4 Wavelength Antenna
20 Meter Vertical Dipole Details
• Vertical 20M Dipole (14.069) with on 16+ Ft Pole and 49+ Ft via Balloon nominal 55 Ohms
• BALUN and/or choke not needed
• Mast needed for Safety & RF as 26 Ft. altitude is required for feed point
• Feed near right angle
Results
Mostly Good Things are:
• Balloon Verticals are superior to Reference Horizontal Dipole by +20 dB Average Rx Gain
• Balloon pulled hidden signals out of noise floor
• Doubled the number of carriers on Panadapter
• CQ at 1 W when checking for SWR got surprize 59 RST Report from 1,200 Miles
• CQ at 25 W got 5,000 Mile 59 RST Report on first call
• In the first Hour mid-day local worked at NA, SA, EU without problems at 25 Watts
• Reverse Beacon Data showed increases for balloon vert dipole reference antenna
+12 dB Average Tx Gain Increase, range measured for 8 dB to 18 dB increasure
The one bad thing is wind speed is a problem. Light winds under 5 MPH are not a problem. Winds at 12 MPH will cause the antenna to be more horizontal. The solution is more lift, bigger balloons, and more cost.