Simple quarter wave ground plane antenna for 446Mhz, all elements measure 15.8cm.
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Slim Jim - As invented by Fred Judd G2BCX
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Four element coax collinear
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Homebrew PMR446 Antennas (Aerials)
Some of my DIY antennas that I have built (purely for receiving of course).
Simple quarter wave ground plane antenna for 446Mhz, all elements measure 15.8cm.
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Slim Jim - As invented by Fred Judd G2BCX
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Four element coax collinear
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When I get a chance, I will detail construction plans for the bottom two antennas.
For the moment (and so I don't forget), here are some measurements for the antennas:
PMR446 Slim Jim
Total length of the Antenna - 459mm
1/2 wave top length - 304mm
1/4 wave bottom length - 153mm
Air gap - 2mm
Gap between the vertical elements - 12mm
Feedpoint (gained from tests) - 31mm from bottom
PMR446 Coaxial Collinear
Top 1/4 wave element - 168mm
1/4 wave coax tuning section - 119mm
1/2 wave coax sections - 222mm
1/2 wave coax sections plus bit more for trimmed ends - 230mm (My antenna had 4 of these)
1/4 wave below bottom coax section for decoupling point - 168mm
Ground radials (2 x 1/4 wave if used) - 355mm
Decoupling tube (if used) - 159mm (?)
