Astroplane base clamp.

SPECIAL NOTE OF CAUTION:
Hold metal sleeve inside black plastic insulator while inserting Tube C. If this is not done and sleeve is moved, a broken connection between coax connector and antenna may develop.

OTHER NOTES:
Tube C connects to inner conductor of coax, and a plastic plug fits into the top of Tube C top stop rain from entering the tube. Tube A, clamp metal body.
When tested on a meter, all parts of the antenna should read short circuit to the coax outer shield. The SO239 will also read as if the antenna is short circuit.

Further information:
  General data.
  Components exploded view.
  Bottom loop.