Someone asked why the VNA graphs do not also show the loss and efficiency of the measured impedance transformer.
The requested values can be calculated in a simple way.
It should be noted that the load resistance used (3203 ohms) and the VNA input impedance (50 ohms) are also measured during the transmission measurement (s21) of the 1:64 impedance transformer.
In addition, because the impedance of the transformer input is not exactly 50 ohms, there is a (small) matching loss that must also be taken into account.
Calculation example for 7.0 MHz (Marker #2)
Impedance at transformer input 47.56-j0.94 ohms
→ Mismatch loss 0.003 dB (calculator by Owen Duffy see below)
Transformer loss=
-|s21|-load loss(load resistance+VNA input resistance)-mismatchloss=
-18.59-(-10*log50/(50+3203))-0.003=-18.59-18.13-0.003=0.457 dB
Transformer efficiency=10^(-0.457/10)=90.0 %
Calculator by Owen Duffy to
Calculate VSWR and Return Loss from Zload (orYload or S11) and Zo
https://owenduffy.net/calc/ZY2Vswr.htm
For those interested: With the ferrite core and compensation capacitor of the 1:64 impedance transformer (above), when wound as a 1:49 impedance transformer, the transmission values shown below result.
At 7.0MHz, the transformer loss is 0.437dB and the transformer efficiency is 90.43%.
The difference is not exactly dramatic - on a real antenna, the different transformation ratios will be particularly noticeable in the lowest and highest frequency bands - also not dramatic, but possibly relevant when working without an ATU.
