Ground Tuner Circuit Diagram by GD4EIP – Practical Wireless Oct 1990

Why build a ground tuner?

The conductivity of your ground varies from one location to the next. This is of particular note to the mobile or portable radio station. Using short vertical or end fed antennas a good low resistance ground is required for efficient operation as you are tuning your antenna against this ground often shown illustrated as a dotted line representing the missing half of the earth side of the dipole.

If your radio station is located in an apartment or double story building then the Ground tuner attached to a suitable counterpoise can act as an Artificial Earth.

Locate a wood dowel or hollow object 37mm in diameter and fasten one end of the copper wire by screw or self tapper and close wind on 13 turns . Then space the turns evenly apart about 3mm by stretching out the coil on the former and fasten the end with another screw.

Next cut some acrylic (Perspex ) to 37mm width and length 110mm. Measure the distance between the screws on your former and centre on the acrylic and drill two mounting holes 3mm.

Parts List

R1: Variable resistor 50k/ohm

S1: Switch single pole 12 way

C1: Capacitor variable 500pf air spaced (1mm

recommended), insulated shaft extension

C2: Capacitor 10nF (103)

D1: Diode point contact germanium diode 1N34 OA91

L1: Toroid T50-2

M1: Meter 50 or 100ma

Montage: Enamelled copper wire 1.8 or 2mm (14swg)and 0.5mm(24swg)

L2: See below

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