On Sun, Sep 8, 2019 at 07:15 AM, Jerry Gaffke wrote:
In that 2018 paper on his website, W7ZOI simulates what a VNA would see using LTSpice.
The spice simulation I was interested in, because it was so basic, was schematic Figure 12 and graph Figure 13. I created a schematic in Eagle and ran the simulation last night and was able to see the results, not surprisingly, were the same as the article. Then I added more probes to plot more points in the circuit. So, I learned more about the T/R switch as well as Eagle and Spice (and every thing nice [sorry]).
The T/R switch operation is mostly discernible by looking at the schematic, yet not trivial. Another reason that made this a good learning exercise. I can now play with trying more power, off resonance frequencies, removing the diodes. I can imagine what will happen in those cases, but fun to see the results using a calculator that not only, in many cases, can grind the math faster than I can on my hand calculator, but grinding out so many additional calculations and plotting them for me.?
Even when I've done things with doing the math by hand, a physical prototype and some final adjustments on the final design is needed, as you pointed out. Of course in Ham Radio home brew, most often, the production model is the prototype.
That VNA you linked is really nice and at a reasonable cost. I may add one to my test equipment assortment. I think the?Antuino can be configured to work as a VNA as well, if I remember from one of the early posts about it.?
Somehow the whole world is connected. From Heathkits, to going to the moon, to full break-in T/R switches that can stand 100 watts.?
Tom, wb6b
