Following from tests conducted and recorded in the previous blog I had to now compare the Z Match output with my Tank Circuit coupler that I have used for many years to feed a 40m end-fed. This was done using additional bench tests in the same manner as before.
I could not match the 3000 Ohms to the tank coupler with 1:1 SWR. The best obtained was a 1.7:1 match. I then substituted the tank coupler with the Z Match. I was able to tweek this to an SWR of 1:1.
Results: Tank Coupler DVM reading = 315mV SWR 1.7:1
Z Match DVM reading = 340mV SWR 1.1:1
Z Match DVM readings = 277mV, 331mV, 330mV, 277mV various settings SWR 1.7:1
Some interesting observations. At the 1:1 SWR on the Z Match the greatest output was obtained. However if the input power is adjusted for SWR 1.7:1 = 93.3% efficiency, thus input power = 1.2*0.933 = 1.11Watts. If I reduce the power input to the Z Match by 6.7% I derive a DVM = 315mV. This being the same as the Tank Coupler. Looking at the Z Match DVM, SWR 1.7:1 readings they are highly dependant on the settings of the capacitors. However they are all in a similar 'ball park'.
Thus I conclude that the couplers have a similar efficiency at least at 7020KHz.
When comparing to the theory. The DVM readings are significantly lower that the calculated value of 463mV (see previous blog). Is this an indication that the loss is attributed to the RF current transducer?