All right. I just bought some coax to replace some old. (Maybe about 20 years old) similar coax. After replacing the old cable I see very little, if any change in antenna system performance. I think I wasted my money. Now I can run this test to see if I needed to change the cable.
In most cases, if water did not get into the cable and the cable itself is made qualitatively, then it can work 50+ years without a large loss of quality.
Near the end, you show the wiggle that varies with frequency. Since, as we travel along the transmission line we will see short and open at quarter wavelength intervals, shouldn't we expect to see more wiggles displayed with the short cable versus the longer cable? So the number of wiggles is really only related to the length of the cable. The vertical size of the wiggle would be related to the loss.
this VNA only goes to 1.3GHz, for 2.4GHz look at: ruclips.net/video/pUjbgnvQ_dM/видео.html if you are rich and have the room in your lab, an old VNA is a pleasure
It really depends on the length of the coax. Lossy coax will still carry a usable signal when the length is short, but try it through a 100 meter length, and that will fail to carry enough signal for most applications, at high frequencies. If you are making measurements, it can be any short coax for the connections, as long as you know the loss of that piece of coax and can take it into account when making the measurement. What can make the process difficult, is when the coax is intermittent.
What a waste of time. The title of this video is "Coax Loss measured on a Smith Chart." You showed on a Smith Chart that there is loss in coax, but you never actually measured it, you never quantified it in any way. After eight minutes and 10 seconds, you finally changed to a log mag display where the actual loss of the coax (actually, twice the loss of the coax) is displayed. You owe me - and everybody else that wasted their time - eight minutes and ten seconds of time. Thumbs down.
I already made a video on the actual measurement: ruclips.net/video/mU71rGUKlBI/видео.html this is an easy way to check your cable on S11 without having to change the setup for S21. Sorry you didn't find it useful. take a look at the other video
@@IMSAIGuy Sure you can check the loss of a cable with magnitude of S11, no need to set up for S21, and there's no need for the Smith Chart. I was doing that 40 years ago. The point is that this video does not show what the title says it will show. You could use the radially scaled parameters at the bottom of the paper Smith Chart - RTN. LOSS [dB] is there, and I see ATTEN. [dB] is there too, although I've never used that one. I saw the title of this video and thought I might learn something. I was disappointed. And I suspect I'm not the only one.
Nice to see the VNA out again, covering new topics!
I love that display so much. Would fit right into a sci-fi. The computer startup in the beginning of Alien comes to mind.
All right. I just bought some coax to replace some old. (Maybe about 20 years old) similar coax. After replacing the old cable I see very little, if any change in antenna system performance. I think I wasted my money. Now I can run this test to see if I needed to change the cable.
And, come back and let us know the results. I've been thinking of replacing a 20+ year old Comet antenna and coax.
In most cases, if water did not get into the cable and the cable itself is made qualitatively, then it can work 50+ years without a large loss of quality.
Nice 3d printed SMA handles
ruclips.net/video/B1h1Kj-NgSw/видео.html
More wizardry. The screen looks
like something Merlin would have
had :-)
You should tell us more clearly why length matters and how each cable measures in dB/meter.
ok, longer is more
nice time spending Sir
What specification defines a cables lossiness? Does the VNA output this value for comparison with the spec (if there is one)?
ruclips.net/video/mU71rGUKlBI/видео.html
cable loss is usually measured in dB loss per 100ft
@@IMSAIGuy ,thank you!
Paying for decreased capacitance and build QA!
I am a beginner and I want to learn and I am trying hard to learn, but my capabilities are limited. Is it possible to help?
here are free books: ruclips.net/video/eBKRat72TDU/видео.html
Thousand of dollars for a coax? For what use case?
making critical measurements in a calibration or R&D laboratory
But can you actually measure the loss as in the title or it's just an qualitative way for looking at the cable?
I'm sure there is a way to back that number out, but you are better off using ruclips.net/video/mU71rGUKlBI/видео.html
looking at the thumbnail I thought he was hacking nasa
In extrem case, low PIM dummy load are made with very long lossy coax... and on your display, mostly all in the center of the chart.
Thank you.
Great to see all the SMA nut widgets in use
Near the end, you show the wiggle that varies with frequency. Since, as we travel along the transmission line we will see short and open at quarter wavelength intervals, shouldn't we expect to see more wiggles displayed with the short cable versus the longer cable?
So the number of wiggles is really only related to the length of the cable. The vertical size of the wiggle would be related to the loss.
you get the wiggle every time it goes around, so more length more wiggles
that's a nice vna. Do you recommend buying an old vna and calib kits if i do some 2.4GHz antenna matchings once in a while ?
this VNA only goes to 1.3GHz, for 2.4GHz look at: ruclips.net/video/pUjbgnvQ_dM/видео.html
if you are rich and have the room in your lab, an old VNA is a pleasure
RG58 is not meant to be used at these high frequencies.
indeed. 21.5 dB loss per 100 feet at 1 GHz
I have to add though, everyone is using RG174 which is worse!
It really depends on the length of the coax.
Lossy coax will still carry a usable signal when the length is short, but try it through a 100 meter length, and that will fail to carry enough signal for most applications, at high frequencies.
If you are making measurements, it can be any short coax for the connections, as long as you know the loss of that piece of coax and can take it into account when making the measurement.
What can make the process difficult, is when the coax is intermittent.
you are right, I was surprised to see such large effects with the short cables I was testing.
What a waste of time. The title of this video is "Coax Loss measured on a Smith Chart." You showed on a Smith Chart that there is loss in coax, but you never actually measured it, you never quantified it in any way. After eight minutes and 10 seconds, you finally changed to a log mag display where the actual loss of the coax (actually, twice the loss of the coax) is displayed. You owe me - and everybody else that wasted their time - eight minutes and ten seconds of time. Thumbs down.
I already made a video on the actual measurement: ruclips.net/video/mU71rGUKlBI/видео.html
this is an easy way to check your cable on S11 without having to change the setup for S21. Sorry you didn't find it useful. take a look at the other video
@@IMSAIGuy Sure you can check the loss of a cable with magnitude of S11, no need to set up for S21, and there's no need for the Smith Chart. I was doing that 40 years ago. The point is that this video does not show what the title says it will show. You could use the radially scaled parameters at the bottom of the paper Smith Chart - RTN. LOSS [dB] is there, and I see ATTEN. [dB] is there too, although I've never used that one. I saw the title of this video and thought I might learn something. I was disappointed. And I suspect I'm not the only one.
OK, fair enough, do a video and I'll point to it
@@IMSAIGuy I might.
If you do not get any value from his video, s ,then WHY watch them.🤔