100 Ft Balloon Antenna

Balloon Vertical Omni-Antennas

Our radio club yearly Special Event (SE) 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 
•    SE mainly a 40M and 20M operation
•    SE is a SSB & CW event (desire to add PSK)
•    SE will be using a 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
o    14.266 MHz Balloon Antenna #1
o    7.255 MHz Cushcraft R7 Antenna
•    CW RIG
o    Primary 7.033 MHz Balloon Antenna #2
o    Secondary 14.066 MHz Balloon Antenna #3 
•    PSK RIG
o    Primary 14.072 MHz Balloon Antenna #3
o    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


•    ¾ WL Vertical 40M Wire (7.035 MHz) into a 99.8 Ft Vertical nominal 55 Ohms assume ground rod at gazebo
•    Vertical 20M Dipole (14.069) with on 16.6 Ft Pole and 16.6 Ft via Balloon nominal 72 Ohms
•    Only 40M using gazebo ground minimizes ground loops, coupling & RFI between RIGs

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
o    Line is tight and secure by weight
o    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%

Wire
•    Messenger vs. weight - Must fly to work
o    #28 AWG Copper tensile strength ~ 22 LBS
o    12 Inch dental floss leader for fatigue (twisting)
•    Insulator
o    30 LB Monofilament X 5 Ft
o    Measured greater than 10 Meg-Ohms

40 Meter 3/4 Wavelength Details
•    ¾ WL Vertical 40M Wire (7.035 MHz) into a 99.8 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 Details

20 Meter Vertical Dipole Details
•    Vertical 20M Dipole (14.069) with on 16.6 Ft Pole and 16.6 Ft via Balloon nominal 72 Ohms
•    BALUN and/or choke not needed
•    Mast needed for Safety & RF as 26 Ft. altitude is required for feed point
•    Feed at right angle
•    Cut Feedline length to 40 or 58 Ft, Avoid 32, 50 or 64 Ft
 
20 Meter 3/4 Wavelength Antenna Details

Results
•    Balloon Verticals are superior to Reference Horizontal Dipole by +20 dB Average Rx Gain
•    Pulled hidden signals out of noise floor
•    Doubled the number of carriers on Panadapter
•    CQ at 25W got Belgium on first call
•    CQ at 5W to adjust SWR got immediate SC RST Rpt
•    In the first Hour worked at NA, SA, EU without problems at 25 Watts
•    Sent 270 CW CQs
•    Got 55 Reverse Beacon Hits
•    Balloon Vertical average distance 1699 Miles
•    Reference antenna average distance 732 Miles
•    +12 dB Average Tx Gain Increase **
•    All logs where increases for balloon antennas
•    Maximum was 18 dB increase
•    Minimum was 8 dB increase




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