By using this system you can obtain a perfect 1:1 SWR anywhere on the 160 meter band. The efficiency of your system will depend on how good your ground system is, as well, of course, how high and clear your antenna is.
The inductor coil was home made from #14 house wire. The insulation was stripped and wire slightly stretched to straighten it. A support frame was made with strips of plastic. Turns spacing was set by cutting slots in the plastic strip.
L1 – 7 turns #14 insulated house wire wound outside L2 (close wound)
C1 – 365 pf broadcast variable
L2 – 17 turns #14 bare, 8 turns per inch, 2.5 inch diameter
C2 – 365 pf. broadcast variable
C3 – 200 pf fixed mica (may need more for difficult tuning situations)
Switch may be used for convenience in adding in the extra capacity (not shown here).
Tuner wire size is not important as currents for typical 100 watt rig are about an amp, at maximum. #14 or #16 ga. wire works well, easy to work with, and keeps its shape
For 100 watts, broadcast receiving capacitor (365 pf variable) is probably OK for C1 and C2. Wider spacing with the capacitor will be needed when running over 100 watts
It is assumed that the transceiver has a SWR meter built in since it is not shown as a separate accessory in these diagrams.
C1 in many cases will require no adjustment as you tune across the 160 meter band. This might not be the case depending on how tightly coupled the two coils are.
C2 covers 1800 to 2000 kHz very nicely. If antenna is different additional capacity provided by C3 might be necessary. Start without C3 until the additional capacity becomes necessary.
Normally a dipole operates regardless of the type of ground system you have. The dipole is a “balanced” antenna and at resonance is half wavelength long. The ground system is not a significant factor in RF radiation with the dipole.
On 160 we find a vertical type of antenna and then “feed it against ground” which is much different way of feeding an antenna.“Feeding against ground” is simply said, but complex in what is involved.With a vertical the antenna is only half of the circuit, while the ground system provides the other half of the antenna system. Thus, an excellent ground system is imperative to the type of antenna being described here. One good benefit of a good ground system, is that it also doubles as a low impedance path for lightning protection. Consult documentation regarding lightning protection for ideas on building your ground system. See also our notes here. Notes on grounding. When feeding against ground, you connect one side of your balanced tuner output to the antenna (this may be the shorted antenna lines mentioned elsewhere, or a long wire). The other connector is connected to your hopefully, good ground system. Thus, your antenna tuner is in the electrical middle: the antenna on one side and your ground on the other. RF to your system is inserted at the tuner.
Is your ground as good as your antenna?
Good luck and welcome to the “TOP BAND”!