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 = 33 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

• Use Feedline length of 50 Ft or 75 Ft, Avoid 32 Ft or 64 Ft


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

• Cut Feedline length to 40 or 58 Ft, Avoid 32, 50 or 64 Ft

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.