Antenna for portable radio devices

An antenna for a portable radio device, including a helical antenna coupled at its base to a transmitter/receiver, said antenna comprising:

• a conductive material helix which includes:
• an upper portion having a pitch which varies according to the height of the helix, decreasing from a lower end of the upper portion to a top end of the upper portion, the electrical length of said upper portion being substantially equal to one quarter-wavelength;
• and a coaxial member including a central core and an outer conductor, said coaxial member extending from a base of said helix to the lower end of said upper portion of said helix and having an electrical length substantially equal to one quarter-wavelength, said core being connected to said upper portion of said helix and forming said helical antenna therewith, said coaxial member being connected to a feed coaxial cable of said helical antenna.

A portable radio device including an antenna for portable radio devices including a helical antenna coupled at its base to a transmitter/receiver, wherein the pitch of a conductive material helix constituting said helical antenna varies according to the height of the helix, decreasing from the base of said helical antenna to its top, said helical antenna being disposed in the top part of a casing of said device, wherein the electrical length of said helix is substantially equal to one quarter-wavelength.

A portable radio device including an antenna for portable radio devices including a helical antenna coupled at its base to a transmitter/receiver, wherein the pitch of a conductive material helix constituting said helical antenna varies according to the height of the helix, decreasing from the base of said helical antenna to its top, said helical antenna being disposed in the top part of a casing of said device, and a retractable whip being inserted in a housing which is part of said casing when retracted and emerging from the top part of said casing when deployed, wherein the electrical length of said helix is substantially equal to one quarter-wavelength.