Dual band GP is like two single band antennas have merged, one rotated by 45° arround the z-axis. Connections are the same for the two antennas: radiator is connected to the same hot-end of the connector, and grounds are connected to the same mass.

This way there is no limit to how many bands antenna can be made. In practice, though, most common are two and three band GP antennas.

dualband gp antenna

For measurements, see the “GP” section.

dualband gp antenna photo

Photo of a commercial dual-band antenna used for long-distance Senao phones

AWX stands for All Wave, and it is shaped like an X. Gain is higher than for dipole antenna, and it can be used in very wide frequency range.

Construction details and Measurements are for Registered Users only.

awx antenna schematics

Schematics for AWX antenna for 2m and 70cm bands

photo of awx antenna

Top-left: frontal view, top-right: side view, bottom: holder

05 radiation pattern

Horizontal radiation is on the left, vertical on the right

06 swr

SWR/Frequency

Multiband Antennas are antennas that can be used for more bands at once, thus they are very practical.

multiband cw sbb dipole multiband dipole 40m 80m 160m
multiband awx 2m 70cm multiband gp ground plane

This antenna covers 65kHz for 160m band, 75kHz for 80m band and the entire 40m band with SWR under 2:1. The tradeoff is limited bandwidth.

multiband dipole

Schematics for Multiband dipole

The coils used are traps for the signal – they act as a notch filters (the windings have capacitance as well).

Construction details are for Registered Users only

We get wire for the coils when we strip the shield from the RG-58 coaxial cable. We thus get only the core – the hot wire, and the first isolation. The coil forms are cut from the PVC pipe.

For the 7MHz trap, we need PVC pipe with 6cm outer diameter. The windings are in two levels: the number of inner windings is 12 turns, and 11 ¼ of outer turns.

The 3.8MHz trap form is made from 3.5” outer diameter pipe. It has 14.3 turns for the inner winding and 13.4 turns for the outer winding.

Use electrical tape to keep the turns in place. Try to make them as tight and closely spaced as possible. Drill the hole in PVC pipe where the winding will enter and exit and secure that hole with hot glue so the coil does not unwind.

This is Inverted V antenna that can be used for both CW and SBB. SBB part is resonant at 3735 kHz, for CW at 3535 kHz.

multiband dipole for cw and sbb

Schematics for Universal Dipole for CW and SBB

12V relays are used to switch between SSB and CW, two coils are used to lower the frequency.

Construction details are available for Registered Users

Operation: When there is no voltage across relays, antenna works in SBB mode. When 12V is applied across relays, inductive elements start to work and antenna works in CW mode. This means that you need 12V power source with a switch as well. Relays are best fed through separate twin-lead cable.

BalUn: if the compact solution is needed, instead of the Air core RF choke, we can use torus ferrite core. Details about construction are in “BalUn” section of the book.

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