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80m end fed half wave tuner.
Tuner design.

The design for this project is of a similar nature as used for the previously constructed 160m and 40m tuners. The design layout shown in this photo shows the tuner components connected to a resistive load and the antenna analyser to give the desired results. The resistive load was determined by using the TuneHalf.exe program. The variable air spaced capacitor is used to tune the circuit to resonance and the antenna analyser is used to confirm both the tap point for best return loss and the point of resonance.
 
 
Component testing layout
 
 
Mid-band frequency response

Here is the display of the analyser giving the vswr reading of 1.00:1 at a frequency of 3.596MHz. The impedance is 50 ohms resistive with no reactive components, which is expected with a carbon resistive load.

 
 
Antenna analyser results
 
 
Measured value of capacitor.

Using the LC meter, here is the value of the air spaced capacitor (separated from the circuit!).
 
 
Measured capacitance
 
 
Measured value of inductor.

Using the LC meter, here is the inductance value of the winding on the toroid core (separated from the circuit!). The green wire is the 50 ohm tap point (which is left un-terminated for this test). You may be wondering why I haven't spaced the windings out more or why there are extra turns. The reason for this is that this core was also being used in a multi-band design - which is still under experimentation.
 
 
Measured inductance
 
 
Final assembly.

Here's the view of the label attached to the cover and the bits installed in the box.
 
 
Project assembly
 
 
Schematic.

Here's the schematic of the tuner. Note that the windings for this tuner are close wound. This will affect the overall inductance and the 50 ohm tap point.
 
 
80m EFHWT schematic
 
       
    2006 - 2009 S.Spirat 
Another SPIRAT initiative