[ARC5] Aicraft Antenna Puzzle

[Robert Eleazer]

Yesterday I took apart a belly mount VHF aircraft band comm radio antenna.  It would receive pretty well but on transmit a field strength meter showed very low output.  It had been bent and I assumed a bad connection down inside the mount.  But what I found was a lead that came from the 22 inch whip, through a small copper coil and then seems to have been coupled to the BNC connector through a surface mount capacitor.  Other whips of that length for aircraft comm just hook direct to coax with no other circuitry.  I know that SCR-274-N HF sets coupled to the relatively short wire antenna via a capacitor but why would they do that for that VHF whip?  Any ideas?

Thanks,

Wayne
WB5WSV     

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