#97: Z vs Zin vs invZ vs revZ Functions

A look at various ways SimSmith can analyze impedance in a circuit and their uses.
www.w0qe.com

[@ae6ty]

A couple of quick notes. First, the lower case 'z' is the 'component impedance' and is available at the outer level in addition to the inside the RUSE block. So, for example, in the given circuit there exists a value 'R1.z' which will be the same as the R1.ohms + j R1.johms. This is particularly useful for reactive components where the impedance is a function of frequency and value. Second, Larry is correct in that SImSmith computes the impedance given the currents and voltages across the component. This can cause confusion if the current or voltage is zero. For example, if you have a load impedance of zero and a shunt resistor R1 in parallel, the impedance of that resistor will be reported as 1e99. Clearly wrong. Just thought I'd point it out! ward

[@alexpacini]

I just wanted to add a quick comment that I think might be interesting. The Comp.revZ requires Z0 in G to be linear, otherwise the expected value might be very different from what is seen in the reality. An example can help: a class E amplifier has an optimal load where it has the ZVS and ZVDS switching. The conjugate of that impedance IS NOT the impedance as shown by the amplifier. In other words, the amplifier expects a particular load but it is not showing an output impedance that is the conjugate of that load. That would have the consequence that the total efficiency would always be below 50% when matched to its ideal load, while in reality an ideal and lossless class E presents 100% efficiency. Great tutorials! SimSmith has many more functionalities than I though. I generally use scikit-rf as an opensource python library for these kinds of analysis, but SimSmith is also good as quick interactive alternative as it seems it can do it in a couple of clicks.

[@wb5mgr]

Very interesting video, would love to know the reference you use to find all of these functions that are undocumented in the manual. I use this program a lot and there are so many functions I appear to not have found. BTW, I really would love to see a video on RF combiners. Feeding multiple transmitter sources into a single antenna or a single source into multiple antennas. I have played with trying to use two or more sessions of the program or with the LG block but I want to know if there is a less kludgy way to do this.

[@w0qe]

WB5MGR, I believe all the "undocumented" features are in one of the 2 manuals but I wouldn't want to have to prove it. Under the help tab there are choices to click on the SImSmith and Anvil programming manual. Give me a couple of examples that you call undocumented. I did a couple of videos on power combiners which were videos #28 & #29 but this has been quite a while and SimSmith has changed and become more capable since then. There are so many topologies for combiners and splitters that doing more videos would be a good idea. Thanks for the comments. Larry, W0QE

[@djm2150a]

Man, I *really* like that extra annotation block you added at ~1:43 showing .Zin, .Z, .revZ, and .invZ. I think you should bug Ward to make that a clickable choice from the SimSmith help menu. :-)Dan, AC6LA

[@ae6ty]

Ya. like you have no influence on SimSmith's evolution :-)

[@baltimore_amp_repair]

Hey Larry. Question for you. What is the easiest way to measure the impedance of an input circuit and output circuit of an Rf amplifier?