Carsten wrote:
"Is it possible to connect a whip type?"

Probably, or perhaps a dipole.

The wavelength is short. You can get antenna gain without connections if
you use reflectors with your existing antennas. The reflecting surfaces
can be plane sheets or grids aligned with the polarization of the
antenna.

You did not give the size of your loop. If the loop has a perimeter of
one wavelength, propagation is broadside to the loop. If it is smaller,
propagation is in the plane of the loop.
Polarization depends on where the loop is fed.

Your wavelength is about 0.7 m.

If a perfect flat sheet is 1/4-wavelength behind your antenna, you may
get about 5 dB gain in the forward direction from the reflector.

Replace the flat sheet with a 90-degree corner reflector, and the gain
rises to 10 dB with 1/4-wave spacing between the antenna and the corner.

11 or 12 dB gain may be obtained by using a 60-degree corner.

For a 1/2-wave dipole spaced either 1/4-wave or 1/2-wave from a
90-degree corner, the gain is about the same (10 dB).

1/4-wave spacing of a 1/2-wave dipole from a 90-degree corner gives a
drivepoint impedance of about 85 ohms.

1/2-wave spacing of a 1/2-wave dipole from a 90-degree corner gives a
drivepoint impedance of about 125 ohms.

As the 1/2-wave dipole without a reflector has a drivepoint impedance of
73 ohms, impedance upset from coupling to the reflector is significant
but not excessive.

See Kraus "Antennas" under the topic: "Corner reflector" for details.

Best regards, Richard Harrison, KB5WZI