V/UHF Superflex Mobile Antenna
Background
A mobile antenna was needed that could withstand the rigors of garaging our SUV without damage. Prior antennas proved to be too stiff when it came to entering a garage. The antenna would bend, vibrate and eventually fail. The idea was to use a similar dual band design for a VHF and UHF antenna (V/UHF) but use materials that could be easily flexed. The four design requirements were:
1) Cover both VHF and UHF bands (146 MHz and 440 MHz repeater bands),
2) Provide reasonable VSWR (less than 2.0:1) across both bands for repeater and simplex operation,
3) Ability to easily flex as the antenna hits the garage door, and
4) Provide a low profile to the casual observer.
The antenna uses a magnetic mount for ease of mounting and, if needed, replacement. The antenna element uses a common, flexible "piano" wire that easily flexes and returns to its original condition. This type of flexible wire is obtainable from hobby and hardware stores.
Design
The Superflex antenna design is shown in the attached drawing. The drawing is in the standard PDF format. The lower right portion of the drawing gives the bill of materials used for the antenna. As usual, you may substitute parts with some changes in performance. You should measure and characterize your final installation to account for small variances in materials or production.
V/UHF Antenna Design (PDF file) ( Download PDF File )
Results
The antenna measurements are shown in the table. The 146 MHz range used an antenna analyzer capable of measuring the real and imaginary components of the impedance. The 440 MHz could only have its VSWR measured.
The photograph of the final installation is shown below.
The magnetic antenna mount is in the lower portion of the photograph.
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