The How of measuring a tuner

The MFJ is a nice convienient package and is shown below in front and back views




They simply most useful tool in measuring tuners and antenna and components is the MFJ line of Antenna Analysers. They are a basic stable variable oscillator, frequency counter, SWR bridge, Resistance and Reactance bridge all in a nice package that runs from 12 volts D.C. Mine has a Vectronics lable but it's MFJ made. Here is a picture of mine.


To measure power I need to measure the voltage across a load that may be just a resistor or a more complex load like a resistor and a inductor. I have the Fluke Model 81RF RMS rf probe which I read the voltage from on my Techtronics Model 422 Oscilloscope. You can see the fluke probe next to the Vectronics in the picture above. The setup I used to make the measurements with is shown below. Notice the scope on the floor and the Fluke probe connected to the MFJ-945B coax output port.


The tuner is a simple design which makes it attractive and the equivelent circuit is easy to draw and is seen below.


The inductor has a Q defined series resistance that can account for loss. Also the shorted turns of the inductor are close to the active part and can dissipate power if it is coupled into that circuit.

To read the results of the first test series click on Data.

Data