Nice presentation. Thanks, I learned a new method for measuring impedance. Here how to measure phase difference automatically with out he need for oscilloscope. Use a fast clock and count V2 from raising edge to raising edge with the help of zero cross detector and a counter. Use a fast clock and count from raising edge of V1 to raising edge of V2 with the help of zero cross detector and a counter. Divide the second # by the first # and multiply by 2PI, and this is your phase. Measure V1 & V2 using a peak detector and A2D converter and do the last two lines.
i know Im asking the wrong place but does anybody know a trick to get back into an Instagram account? I stupidly forgot my account password. I love any tricks you can give me.
@Lian Ellis Thanks for your reply. I found the site on google and im waiting for the hacking stuff now. Takes quite some time so I will reply here later with my results.
From what I have seen, most single port VNAs work like this so this could be easily be titled VNA basics or something like that. Very nice presentation, as usual.
Dragan, You are correct that many (maybe most) of the little VNAs work like this. However as I mentioned near the end of the video other circuits such as a dual directional coupler could also be used but the detection circuits would need to be more sensitive. I struggle with titles for videos all the time. The title can't be too many words and I want it to be understood by most folks, I don't want it to be "click-bait", etc. Glad you enjoyed the video. Larry, W0QE
Larry, this is a good video, and I think it will be very useful for most people. I guess the same thing could be done in Excel, but you don't have the nice Smith chart visualization about how close the calculation is. Anyway, this was one of your best.
Tom, Yes, the complex math help could come from SimSmith or several other programs like Excel, Matlab, Mathematica etc. but you're right that having the Smith Chart visualization is really nice. I have done the complex math manually many times (which is good practice) but it is very easy to make mistakes. Thanks for the comment. Larry
This technique can be used to measure the RF impedance of any circuit but with an oscilloscope being the detector the voltage levels will need to be fairly large and you need to be careful not to damage the front end of the receiver. S9 is typically a signal of about 50uV so a voltage of 100mV would be S9+66dB and 100mV will barely be enough unless you have a pretty good scope. A receiver that is mismatched to the antenna + feed line will suffer what I have mentioned as mis-match loss in previous videos. The mis-match loss for a 3:1 SWR is only 1.25dB so little is to be gained in the HF region where band noise dominates receiver noise. At higher frequencies this is not the case but you should probably be most interested in the input impedance of a receiver with the pre-amp enabled and again you need to be careful not to damage the receiver. Larry, W0QE
I setup the circuit, pasted the the first line of the calculation Wave("V1pk", V1, V); but got the error"Wire, variable, or component already declared or built in:V1". What am i doing wrong here?
I see that you got the problem fixed. This can be a little confusing since many of the parameters are optional. Look at video #69 where I went through many of the options. Larry, W0QE
Nice presentation. Thanks, I learned a new method for measuring impedance.
Here how to measure phase difference automatically with out he need for oscilloscope.
Use a fast clock and count V2 from raising edge to raising edge with the help of zero cross detector and a counter.
Use a fast clock and count from raising edge of V1 to raising edge of V2 with the help of zero cross detector and a counter.
Divide the second # by the first # and multiply by 2PI, and this is your phase.
Measure V1 & V2 using a peak detector and A2D converter and do the last two lines.
Here's a link to a video that I did that shows this technique using an analog scope:
th-cam.com/video/eYN7dhdt1Dw/w-d-xo.html
i know Im asking the wrong place but does anybody know a trick to get back into an Instagram account?
I stupidly forgot my account password. I love any tricks you can give me.
@Jacoby Theo instablaster :)
@Lian Ellis Thanks for your reply. I found the site on google and im waiting for the hacking stuff now.
Takes quite some time so I will reply here later with my results.
@Lian Ellis It worked and I now got access to my account again. Im so happy:D
Thank you so much you saved my account!
@Jacoby Theo happy to help :)
From what I have seen, most single port VNAs work like this so this could be easily be titled VNA basics or something like that. Very nice presentation, as usual.
Dragan,
You are correct that many (maybe most) of the little VNAs work like this. However as I mentioned near the end of the video other circuits such as a dual directional coupler could also be used but the detection circuits would need to be more sensitive. I struggle with titles for videos all the time. The title can't be too many words and I want it to be understood by most folks, I don't want it to be "click-bait", etc. Glad you enjoyed the video.
Larry, W0QE
Larry, this is a good video, and I think it will be very useful for most people. I guess the same thing could be done in Excel, but you don't have the nice Smith chart visualization about how close the calculation is. Anyway, this was one of your best.
Tom,
Yes, the complex math help could come from SimSmith or several other programs like Excel, Matlab, Mathematica etc. but you're right that having the Smith Chart visualization is really nice. I have done the complex math manually many times (which is good practice) but it is very easy to make mistakes. Thanks for the comment.
Larry
I enjoyed the video, thank you.
Glad you enjoyed the video John.
Larry, W0QE
Can this method be used to mesure the unknown impedance of a receiver at a specific freq? In order to build an antenna for it?
This technique can be used to measure the RF impedance of any circuit but with an oscilloscope being the detector the voltage levels will need to be fairly large and you need to be careful not to damage the front end of the receiver. S9 is typically a signal of about 50uV so a voltage of 100mV would be S9+66dB and 100mV will barely be enough unless you have a pretty good scope. A receiver that is mismatched to the antenna + feed line will suffer what I have mentioned as mis-match loss in previous videos. The mis-match loss for a 3:1 SWR is only 1.25dB so little is to be gained in the HF region where band noise dominates receiver noise. At higher frequencies this is not the case but you should probably be most interested in the input impedance of a receiver with the pre-amp enabled and again you need to be careful not to damage the receiver.
Larry, W0QE
I setup the circuit, pasted the the first line of the calculation Wave("V1pk", V1, V); but got the error"Wire, variable, or component already declared or built in:V1". What am i doing wrong here?
Problem fixed after upgrading to Version 16.6, thank you.
I see that you got the problem fixed. This can be a little confusing since many of the parameters are optional. Look at video #69 where I went through many of the options.
Larry, W0QE