RG58 coax pictures
On a different tack I came across this on qrz and thought it would be useful info to anyone using a VNA. First the data from measuring a 50 Ohm dummy load as a reference point..
1. LogMag ——————————————— 10dB / -30.6 dB 2. Phase ———————————————— 90degrees / -1.786 degrees 3. Delay ———————————————— 1000p / signal varying between -1.3ns and 0.966ps 4. Smith ———————————————— 1.0FS 47.1Ohms 700nF 5. SWR ————————————————- presents 1.06 the ratio part of vswr. 6. Polar ————————————————- 1.0 FS -0.029 -0.029j (again means nothing to me) 7. Linear ———————————————— 125m / 0.029 8. Real ————————————————– 250m / 0.029 9. Imag ————————————————- 250m / 0.000j 10. Resistance —————————————– 100 / 47.1 ohms 11. Reactance —————————————— X 100 / -64.7 mOhms
Many of these options show the same information in slightly different ways. When you are making One port measurements. (Using just one connector of the VNA), Some of the parameters are not very useful. The first number before the slash/ is the scale so the first one is 10dB per vertical division.
1. LogMag means that you are taking a return loss measurement. You only have the magnitude and it will report the value in dB scale. This is not a vector measurement by itself. Return loss is really just another way to look at VSWR. The reflected signal energy is lower if the match to the transmission line is good. If you are interested you can look up conversion between return loss and VSWR. It really is just the same thing with different units.
2. Phase. If you combine this with the Log mag measurement then you will have a vector measurement. You will know how much the reflected energy is reduced from the LogMag and you will know what angle the reflected signal is relative to the forward signal. You can convert this vector measurement magnitude and phase to the other ones if you wish by math transformations.
3. Delay. This is normally used for a two port measurement, but it really is another way to look at the delay if using a one port measurement. Not really meaningful and prone to errors for one port measurements.
4. Smith Chart. Just a visual way to look at complex impedance measurement. Same info as from LogMag and Phase. If you like it use it. If not use one of the others. 5. SWR. I think you get this one. 6. Polar. Just another way to visualize the magnitude and phase. 7. Linear. This is just the normalized magnitude of the reflected signal but in linear units instead of log (dB) 8. Real. This is the normalized resistive part of the impedance measurement. 9. Imag. This is the normalized imaginary or reactive part of the impedance measurement. 10. Resistance. This is probably the thing that is easiest to understand. This is the un-normalized real resistance of the impedance.