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Making a tuner for an end fed half wave antenna for 160m.
In the beginning...

The time had come to try a half wave on 160m. No ground radials required. Minimum ground losses = more radiated rf. That's the theory. I found a program on the internet that helped provide a starting point for the tuner.

TUNEHALF.exe by the late R.J.Edwards, G4FGQ, usually available as a free download from the internet.

A screenshot of the opening page of the program, is shown below:
 
 
TuneHalf program main page
 
 
Let's start.

When you press E, you are taken to the data entry screen, shown below. This is where we enter our initial data.

 
 
160m data entry
 
 
Input the data.

I've entered the data and then modified the variables using the hot keys, to give the desired values that I think should work.
i.e. change the antenna height so the length is electrically closer to being a half wave, for example.

 
 
160m data entry
 
 
Analysis of the results.

From the data displayed, we can see that the coil Q is reasonably high (495) but the overall circuit Q is low (8.3). This will mean that very little tuning, if any, will be required to cover the band.
So, let's confirm the coil winding details and inductance using the mini-ring core calculator, as used in a previous project. Let's use 43 turns, 91mm diameter by 265mm long. This can also be used to find out how long the coil wire needs to be, as a minimum.
 
 
160m inductor
 
 
Let's start building ...

Collect the bits we need and arrange placement. The plastic coil former was made from the bottom of a computer keyboard.
 
 
160m EFHW Tuner - inside view
 
 
Connect and test.

The load impedance is about 4700 ohms, so let's use a 4k7 ohm resistor as the load and see where it tunes up.
Best swr can be determined by using an alligator lead and a scalpel blade initially (to pierce the coil wire insulation), to find the best matching point, after the variable capacitor is tuned for the desired frequency.
 
 
Inside 160m EFHW tuner
 
 
Reasonable vswr reading for a resistive load. What will a true antenna test show?
160m EFHW vswr
 
 
On air test

Let's go and test it out! Where else could you have 80 metres of wire in the air?!!!

 
 
The radio, tuner and kite wire restraints.
160m EFHW tuner setup on the beach
 
 
80m of wire rising steadily into the air. Pretty strong wind this day and no one on the beach.
160m half wave antenna
 
       
    2006 - 2009 S.Spirat 
Another SPIRAT initiative