Excellent teaching i am an old electronics engineer but not a RF expert i was searching for videos about coax cable impedance i did not get any thing until i found this video .Thanks sir you are a brilliant teacher better then other English teachers.
Thank you so much for making this video and simply explaining this subject. I knew about what you explaining but it didn't cross my mind how to be able to simply work out the impedance.
I never even gave a though ever for testing an unknown coaxes impedance. Great demonstration on how to do so! I think I'll try it here dor the heck of it using my DE 5000. Also. Thanks for showing us the receive and transmit impedance chart for coax. Now it easily understood by me why the compromise for 50ohm coax for ham, cb, etc. usage is used. Happy New Year Peter! 73 Tom
I've heard about this topic many times, but only now I'm sure I'll remember how it actually works. Thank you very much for this great explanation and demonstration.
Great stuff! And you got me to buy the same calculator you have! Haven't bought a calculator since 1986, when I bought my HP 16C calculator for programmers. Still works today, but I remember laughing back then when I read the instruction manual that it could do calculations on 64-bit numbers. I never imagined that I would have access to that kind of power. Now you have it in your phone. :)
Hi Jack, yeah when I saw the calculator 2 year ago or so I couldn't resist and bought it LOL. Technology is really improving fast..Thanks for watching 73
Peter, Thank you for this great video! You are teaching an old Dog new Tricks all the time! Please keep the Class room videos coming! 73's de K8KEM David from Ohio
Very interesting and informative. A technique that needs no new or specialised equipment which is a good thing at this time of the year. Thank you for the videos from 2016 and I hope you feel motivated to produce more in 2017, they are appreciated.
Good Morning Peter, this is a real eye opener for 50 OHMS. Thank you for your video on the thus subject and your explanation on L &C. Happy New Year best to your family.
It's always useful to have some tips about coax cable. Wit coax being very expensive, it's also ways necessary to re-use it again if it is still in good condition.
Very useful demonstration how to measure and how to use the coaxial cables : 75and 50ohms. I did not know about this difference of impedance , for receiving and transmitting purposes thank you for easy and practical video.
Hi Peter, Great video. Earlier this year I bought an MFJ-269 off Ebay to determine how much 50 ohm coax I had left on a 250 ft spool that was 30 years old. It showed I had 135 ft and when I measured the length it was 126 ft. Close enough for government work. HiHi 73 and Happy New Year WB3BJU
Nice one Peter! It should be pointed out that you can always use coax with larger diameter to handle more power but then the cost is higher. Impedance is related to the conductor spacing, the dielectric constant of the insulating material and also the center conductor diameter. Lowest loss coax will have a mostly air dielectric with large center conductor diameter and correspondingly large outer diameter with correct ratios to make the impedance come out to what you want. 73's and Happy New Year!
Very interesting - thanks. It would also be fun to perform the measurement by putting a signal generator and an oscilloscope at one end, and a variable resistor at the other. Then tweak the variable resistor to minimise the reflection and read off the cable impedance by measuring the resistance. I always wondered why 50ohm was used in some applications and 75ohm in others: it's interesting to learn that there really is a very good reason !
Great video. This formula is working for any transmission line, not only coax cables. Its general form is Z0=sqrt(Zs.c. x Zo.c.), where Zsc and Zoc are complex impedances so the imaginary part gives an information about the losses. So this measurement can also be done with a miniVNA :)
2:40 comment. It's not always easy to get old cable data by looking up whats printed, e.g. try to search some odd Chinese brand. These are often sold without any real product codes and thus lack proper identification for the cable itself. In addition you may find very limited technical information on the web site (if any information exist at all). Your tip is thus very useful. Thank you Peter.
Except he pronounces some words wrong. Coax is pronounced co-axe not coax. He does similar with the word balun which is pronounced bal-un not balloon. Cable too which is kay-bull not cobble.
Always look forward to your instructional and informative videos Peter. I wonder if my MFJ 259b could make those L C measurements ? Happy New Year ! ! !
When I was in school for Physics we tested the velocity factor and impedance. I don't have a specific pulse generator to use at home and I'm wondering if there's a circuit I can build to convert my simple frequency generator to do so. Maybe a a square wave with duty cycle set short and an active RC filter ???
Hi Peter. Really enjoyed your video on determining the impedance of feed lines, and especially about how the use of 75 and 50 ohm coax came about. I was also wondering if you determined the number of significant digits or figures you had in your measurements of capacitance and inductance. I could not see all of the measurements on your meter so I am not sure how many significant digits or figures you were able to read. If you only had one significant digit or figure for example in one of your measurements then only the 5 in the 50 ohm measurement, the 7 in the 75 ohm measurement and the 4 in the 400 ohm measurement would be significant.after the calculations, If this case then measuring longer lengths of cable may give you more significant digits or figures and a greater degree of precision if your meter is precise ,or more accuracy if your meter has been calibrated to a standard. Please give me your thoughts, and please keep making the videos I have learned so much from you. Thanks again John C
Hi John, yes the challenge for the meter is higher with a short test lengths so it is always good to improve the general conditions. Thanks for watching 73
Thanks for sharing your knowledge and measurements. One issue in your first calculation (12:50 in video) is misnaming/labeling inductance as Farad rather than Henry. Simply an oversight and the concept and procedure are clearly communicated.
Awesome video! Learned a lot from you! Btw... Your voice totally reminds me of "Hans Oberlander" from the game Gran Theft Auto San Andreas as the radio DJ SF-UR. :)
Thank you. Very useful and educational information. I have a request - please show how it is possible to test the effective shielding on coaxial cable. I have some new stuff with more dense braid and some with less dense braid and I would like to know the difference regarding RFI (shield effectiveness) etc. Also, I have some old and some used coax - is it still good regarding loss and RFI. 73 joe n8ea
Thanks for feed back Joe. Well a real shielding factor measurement is a bit complex to perform in my lab. Bur I remember a kind of predicting approach may be that could be done with the equipment I have.. Let's see. 73
Could the impedance of the ladder line be changing due to proximity of conductors near it? I know that's a big problem when using ladder line since it is unshielded. Would it read differently out in the open away from objects on your bench? Thanks for a very informative video.
If 75 ohm cable has a lower loss but we don't we use it for transmitters because of the power handling, what about low power transmitters? Would not 75 ohm be a better choice because of the lower loss if only a small amount of power needs to be handled?
Perhaps the symmetric cable is meant to operate at a frequency that is different than the test frequency of the meter. What I'm saying is that the cable might be 450 ohms at MHz frequencies rather than kilohertz.
Thank you again for teaching me something I did not know Peter. So, if I understand it correctly, the values in the formula should be (L) in Henrys and (C) in Farads. Not in uH and pF?
Bora, you have to use the readings displayed by your meter to use it correctly in the formula. The link is helping to put the right exponents into the formula. 73
It might be nice to clarify even more that you measured absolute capacitance and inductance, and not per unit of length. Yet those would cancel out in the ratio between L and C. The formula for the transmission line impedance is indeed derived from specific not absolute values. this might ground better the intuition. What do you think?
Video yang sangat bagus...ini adalah perhitungan nilai z yang paling akurat menurut saya dari berbagai tutorial di youtube.... Ada pertanyaan sedikit .... Adakah cara yang paling sederhana untuk menemukan nilai z? Misalnya menggunakan multimeter. Terimakasih.......
well done my question is usually we match 50 ohm radio with 50 ohm impedence of antenna but still how RF is transmitted in air when impedence of air is around 300 ohm?
Hi Adnan, thank you! Sorry I'm not able to follow up all e-mails....simply to many.... Z(W) free space vacuum = 120x pi x ohm=376 Ohm. That is a nature given constance and describes the condition in the far-field of an antenna. The condition in the close-field is very much more complex and different to the far-field condition... 73
I bought one of those Ebay LC meters on the strength of what you show here but I can't achieve anything like the kind of accuracy that yours does. I've even tried measuring long pieces of 50ohm coax (M&P airborne 5) and the closest I could get was 60 ohm. I was as far off as 250ohms when measuring a short piece of RG58. I'd love to try this with something that might be a little more accurate and reliable one day.
TRX Bench yeah I'm going to try and do a few other tests over the weekend. I should be able to measure an inductor with my scope and signal generator and compare the impedance with a known resistor to get a ball park figure to compare it with.
danke fuer die super erklaerung. wie erklaert man das power handing von 450 Ohm ladder line und high power application? kannst Du bitte eine video machen mit dem nanoVna als test geraet? merci
great video, is it possible to work out what mix ferrite rings are, I have a few and not sure what type they are...I did see a video once on how to check ferrite rings for certain applications..but that was long ago...thanks ! 73s
Thank you Cliff. Well the best is to measure the core material out. You get an idea on which frequency the material work and can decide if it fits into your project. In video #101 I show how an unknown ferrite can be tested... Hope that helps 73
Please help one problem: I bought a 50 ohm cable with velocity factor 82 and it does not work on the cb antenna. the capacity is the same 80pf / m but measured capacity at one end with the length of 10m it has double capacity compared to rg58
Yes Thank you this video was of great importance to me, another wonderful small link in the secretes of the Universe hi hi I have been lookin for this formula for a long time, this video is going to make learning so much more exciting, Sincere Thanks VK4JDJ
hello thank you for this video I would like to know which cable is used for measuring devices (oscilloscope, counter) is it possible to make them yourself thank you
Lab & test equipment with coaxial terminations almost always expects 50 ohm cable, with narrow exceptiions, such as specialized gear meant field use in the CATV industry. In theory you could make your own coaxial cable, but would need precise and consistent control over its geometry (inside diameter of outer shield layer, outer diameter of center conductor, and dielectric constant of insulating material in between together determine impedance), also taking care to ensure good shield coverage to avoid leakage of RF, whether ingress or egress. Air-core coax can be assembled using two sizes of pipes nested within one another using spacers to keep them centered on the same axis, great for high power handling, but you then need a way to draw & keep moisture out.
Erstmal ein gesundes erfolgreiches 2017, wieder mal ein tolles Video, ich muß jetzt auch mal meine Reste durchmessen. Ich hab nur eine verständniss Frage, wie kommt die Einheit Ohm zustande wenn ich nH durch pF teile? 73 DO1BSW
Hall Bernd, vielen Dank und ein Frohes Neues Jahr! Ja das ist eine sehr gute Frage. Formeln enstehen immer durch Herleitung von sehr komplexen Zusammenhängen, so auch hier. Die Herangehensweise an das Thema geht über das Ersatzschaltbild einer Koaxleitung und die sich daraus ergebenden Differenzialgleichungen für U und I. Durch einsetzen und wegkürzen kommt man am Ende auf die vereinfachte Formel wie im Video dargestellt. Du merkst aber sicher schon über diesen Ansatz das sich dhinter komplexe Mathematik über die imaginären Inhate ergibt. Hoffe das hilft erst einmal...73
On twin antena CB set up, we use a RG-59 75ohm "Y" harness Is it because we need to rise the impedance because we run parallel antenas? (Parallel mean half impedance of a single antena)
I believe you both are correct in the answers. Yes it is because the impedance is a slight bit different but also this acts like a transformer to correct the impedance difference. That is what I understand about the "Y" harness setup. So you both answered the question but it also depends on the frequency and coax length. Coax is not 75 ohm the whole length. At a given frequency it is at certain lengths but that is a more complex way to look at it.
A dated video but still great. How about giving us an updated video on how to do the same thing with a nanoVNA as they are now cheap enough that anyone can afford one? 73, KD4LLC
Would a multimeter not work 🤔 measuring the legs of the cable and divide it to 1 cm and than multiply by 100 to get to the 1meter length and putting than the measured ohms in 🤔
I thought 300 ohm (ladder) twin lead type is better for receiving signals (lower loss), however interference is a problem with twin feed lines. Here's an interesting concept for HAM radio; Use different feed lines and antenna (30 ohm for TX and 75ohm for RX) Not practial but efficient. No body like standing waves that can cook you.
Excellent teaching i am an old electronics engineer but not a RF expert i was searching for videos about coax cable impedance i did not get any thing until i found this video .Thanks sir you are a brilliant teacher better then other English teachers.
Thank you so much for making this video and simply explaining this subject. I knew about what you explaining but it didn't cross my mind how to be able to simply work out the impedance.
Thanks for feed back. All the best and HNY 73
I never even gave a though ever for testing an unknown coaxes impedance.
Great demonstration on how to do so!
I think I'll try it here dor the heck of it using my DE 5000.
Also. Thanks for showing us the receive and transmit impedance chart for coax. Now it easily understood by me why the compromise for 50ohm coax for ham, cb, etc. usage is used.
Happy New Year Peter!
73
Tom
Hi Tom, glad to see you ! Hope you are doing well. Thanks for watching and a Happy New Year 2017 to you and yours 73
I've heard about this topic many times, but only now I'm sure I'll remember how it actually works. Thank you very much for this great explanation and demonstration.
Very good explanation, and very practical, Have never seen anybody shoing this in practice!!! congratulations!!
Great stuff! And you got me to buy the same calculator you have! Haven't bought a calculator since 1986, when I bought my HP 16C calculator for programmers. Still works today, but I remember laughing back then when I read the instruction manual that it could do calculations on 64-bit numbers. I never imagined that I would have access to that kind of power. Now you have it in your phone. :)
Hi Jack, yeah when I saw the calculator 2 year ago or so I couldn't resist and bought it LOL. Technology is really improving fast..Thanks for watching 73
Peter, Thank you for this great video! You are teaching an old Dog new Tricks all the time! Please keep the Class room videos coming! 73's de K8KEM David from Ohio
Hi David, it is really a honer that you like it! Thanks for watching 73
Very interesting and informative. A technique that needs no new or specialised equipment which is a good thing at this time of the year. Thank you for the videos from 2016 and I hope you feel motivated to produce more in 2017, they are appreciated.
Thank you very much Happy New Year.
Another great video showing how to test cable impedance Peter. Thanks for sharing this and taking the time to do so. Happy New Year to you and yours .
Thank you Buddy! HNY 73
Good Morning Peter, this is a real eye opener for 50 OHMS. Thank you for your video on the thus subject and your explanation on L &C. Happy New Year best to your family.
Thank you Dennis Happy New Year 73
It's always useful to have some tips about coax cable. Wit coax being very expensive, it's also ways necessary to re-use it again if it is still in good condition.
Thanks for feed-back! All the best Cheers.
Very useful demonstration how to measure and how to use the coaxial cables : 75and 50ohms. I did not know about this difference of impedance , for receiving and transmitting purposes thank you for easy and practical video.
Thanks for feed-back 73
you're the best teacher.all it's more simple with your explanations.thank you and happy new year
Thank you for your kind feed-back Jose! Happy new year 73
Despite of my poor english I could follow easely. Tank you it was very clear
big thank teacher, I have been searching for this kind of explanation so long :)
That was fabulous! I never got a straight answer to that question until now.
Hi Peter,
Great video. Earlier this year I bought an MFJ-269 off Ebay to determine how much 50 ohm coax I had left on a 250 ft spool that was 30 years old. It showed I had 135 ft and when I measured the length it was 126 ft. Close enough for government work. HiHi 73 and Happy New Year WB3BJU
very good all is possible :^) Thanks for stepping in Happy New Year 73
Very useful. I have a reel of coax in the workshop with no data on it, this is a great help. !
Glad that you like it Simon and thanks for watching Cheers
Nice one Peter! It should be pointed out that you can always use coax with larger diameter to handle more power but then the cost is higher. Impedance is related to the conductor spacing, the dielectric constant of the insulating material and also the center conductor diameter. Lowest loss coax will have a mostly air dielectric with large center conductor diameter and correspondingly large outer diameter with correct ratios to make the impedance come out to what you want. 73's and Happy New Year!
Hi Herbert, yes I agree thus it is good to have a practical compromise.. Thanks for watching 73
Hi, happy new year Peter. Very interesting video, especially the info about why we have 50 and 75 ohms cables.
73, Thomas
Happy new year Thomas and thanks for watching my videos! 73
Very interesting - thanks. It would also be fun to perform the measurement by putting a signal generator and an oscilloscope at one end, and a variable resistor at the other. Then tweak the variable resistor to minimise the reflection and read off the cable impedance by measuring the resistance.
I always wondered why 50ohm was used in some applications and 75ohm in others: it's interesting to learn that there really is a very good reason !
Thank you for feed-back. Yes I have done a very early video on open end coax and shorted end to determine the length of a coax. 73
Great video. This formula is working for any transmission line, not only coax cables. Its general form is Z0=sqrt(Zs.c. x Zo.c.), where Zsc and Zoc are complex impedances so the imaginary part gives an information about the losses. So this measurement can also be done with a miniVNA :)
you are right 73
2:40 comment. It's not always easy to get old cable data by looking up whats printed, e.g. try to search some odd Chinese brand. These are often sold without any real product codes and thus lack proper identification for the cable itself. In addition you may find very limited technical information on the web site (if any information exist at all). Your tip is thus very useful. Thank you Peter.
Glad that the video makes sense to you! Thanks for feed back 73
Very interesting test and calculation,very informative many thanks,Colin.
it's 2021 outside.
I'm learning from you.
thank you.
very good glad that you liked it
You are an amazing person dear....many many thanks to you... your a wonderful person 🌺💐
Thank you Mohamed!
Well done Peter. Wish I had your flashy calculator 30 years ago :)
LOL yes Joe me too :^). Thanks for watching 73
Thank you Peter - very well explained and your English is super!
Except he pronounces some words wrong. Coax is pronounced co-axe not coax. He does similar with the word balun which is pronounced bal-un not balloon. Cable too which is kay-bull not cobble.
Hi Peter and family here's wishing you a very good new year, take care
Thank you Peter! Have a Happy New Year 73
Hello Peter,
Great video. Very well explained.Looking forward for more of such informative videos. Vilen Dank
73's VU3RSA
Thanks for feed-back. 73
Very good video. Thank you! Your English pronunciation is very good also.
Thanks for the feed-back Richard, glad you like it 73
Много интересно и полезно видео. Благодаря !
Very interesting and useful video ! Thanks and Happy New Year !
Happy New Year and thanks for watching 73
Happy New Year Peter. Love your videos.
Thank you and Happy New Year
Thank you sir. Much understandable than a natural english speaker
Phooey, and I spent all those $$ on a TDR box! Happy New Year Peter! 73 - Dino KL0S
LOL so the money goes.. Thank you Dino a Happy New Year to you and yours ! 73
Nice video Peter as always. Happy New Year from Brazil
Thank you Mauricio! Happy New Year 73
Happy new year from Australia mate
Happy New Year Willy! 73
Always look forward to your instructional and informative videos Peter. I wonder if my MFJ 259b could make those L C measurements ? Happy New Year ! ! !
Thank you Bob all the best and Happy New Year 73
Great video thanks I learned a lot💜👍
Great information well delivered. Thanks.
Thank you
Great tip ! Many thanks for your interesting videos. Thumbs up :)
You labeled the inductance as capacitance on the first maths and it's making me crazy.
nice demo good work thank you have a great New Years Peter
Thank you Dennis! Happy New Year 73
Good well thought out demo/talk... Good one Peter!
Thank you HNY
Just Awsome Explaination.. Keep doing it !!!
When I was in school for Physics we tested the velocity factor and impedance. I don't have a specific pulse generator to use at home and I'm wondering if there's a circuit I can build to convert my simple frequency generator to do so. Maybe a a square wave with duty cycle set short and an active RC filter ???
Hi Peter. Really enjoyed your video on determining the impedance of feed lines, and especially about how the use of 75 and 50 ohm coax came about. I was also wondering if you determined the number of significant digits or figures you had in your measurements of capacitance and inductance. I could not see all of the measurements on your meter so I am not sure how many significant digits or figures you were able to read. If you only had one significant digit or figure for example in one of your measurements then only the 5 in the 50 ohm measurement, the 7 in the 75 ohm measurement and the 4 in the 400 ohm measurement would be significant.after the calculations, If this case then measuring longer lengths of cable may give you more significant digits or figures and a greater degree of precision if your meter is precise ,or more accuracy if your meter has been calibrated to a standard. Please give me your thoughts, and please keep making the videos I have learned so much from you. Thanks again John C
Hi John, yes the challenge for the meter is higher with a short test lengths so it is always good to improve the general conditions. Thanks for watching 73
Thanks for sharing your knowledge and measurements. One issue in your first calculation (12:50 in video) is misnaming/labeling inductance as Farad rather than Henry. Simply an oversight and the concept and procedure are clearly communicated.
Thanks for feed back Bill! Yes off course simply a slip..sorry for that. 73
Awesome video! Learned a lot from you!
Btw... Your voice totally reminds me of "Hans Oberlander" from the game Gran Theft Auto San Andreas as the radio DJ SF-UR. :)
Thanks for watching but I don't know Hans Oberlander lol
Good work, thanks and Happy New Year
Thanks for watching and Happy New Year 73
You should always put a link to the devices you are using. People want to buy them. Not sure how to find that measuring device, I want one. Thanks
Many thanks for your explanation
Thank you. Very useful and educational information. I have a request - please show how it is possible to test the effective shielding on coaxial cable. I have some new stuff with more dense braid and some with less dense braid and I would like to know the difference regarding RFI (shield effectiveness) etc. Also, I have some old and some used coax - is it still good regarding loss and RFI. 73 joe n8ea
Thanks for feed back Joe. Well a real shielding factor measurement is a bit complex to perform in my lab. Bur I remember a kind of predicting approach may be that could be done with the equipment I have.. Let's see. 73
Could the impedance of the ladder line be changing due to proximity of conductors near it? I know that's a big problem when using ladder line since it is unshielded. Would it read differently out in the open away from objects on your bench? Thanks for a very informative video.
Yes you are absolutely right! I thought I have said it in the video but I have missed it. Thanks for the addition and for stepping by. 73
If 75 ohm cable has a lower loss but we don't we use it for transmitters because of the power handling, what about low power transmitters? Would not 75 ohm be a better choice because of the lower loss if only a small amount of power needs to be handled?
Thanks TRX Love you work. Keep it going!
Thank you Phillip! 73
Curious as to why you cut off a short piece? If the ratio is always the same, why not just test the entire length of cable?
Loved this video. Heartily thankful
Thank you Cheers
Perhaps the symmetric cable is meant to operate at a frequency that is different than the test frequency of the meter. What I'm saying is that the cable might be 450 ohms at MHz frequencies rather than kilohertz.
Briliant video, very pratical and informative. Now I would like to know a simple way to measure the impedance of an existent antenna. Thanks.
Well that is a bit more complex but a device like the miniVNA will do it..73
Thank you again for teaching me something I did not know Peter. So, if I understand it correctly, the values in the formula should be (L) in Henrys and (C) in Farads. Not in uH and pF?
take a look at this article: en.wikipedia.org/wiki/Metric_prefix
Bora, you have to use the readings displayed by your meter to use it correctly in the formula. The link is helping to put the right exponents into the formula. 73
Wirklich tolle Videos , vielen Dank dafür .
Ich wünsche einen Guten Rutsch und viel Erfolg und Gesundheit für das Jahr 2017 .
Vielen Dank für die guten Wünsche! Auch für DIch und Familie eine Gutes Neues Jahr ! 73
Happy new year Peter.
Happy New Year Howard
It might be nice to clarify even more that you measured absolute capacitance and inductance, and not per unit of length. Yet those would cancel out in the ratio between L and C. The formula for the transmission line impedance is indeed derived from specific not absolute values. this might ground better the intuition. What do you think?
Video yang sangat bagus...ini adalah perhitungan nilai z yang paling akurat menurut saya dari berbagai tutorial di youtube....
Ada pertanyaan sedikit ....
Adakah cara yang paling sederhana untuk menemukan nilai z? Misalnya menggunakan multimeter.
Terimakasih.......
;Nice video, and while I'm here guten nie Jahre, vielen Dank für die content 2016
Thank you Joop! Happy New Year! 73
well done
my question is usually we match 50 ohm radio with 50 ohm impedence of antenna but still how RF is transmitted in air when impedence of air is around 300 ohm?
Hi Adnan, thank you! Sorry I'm not able to follow up all e-mails....simply to many.... Z(W) free space vacuum = 120x pi x ohm=376 Ohm. That is a nature given constance and describes the condition in the far-field of an antenna. The condition in the close-field is very much more complex and different to the far-field condition... 73
NICE lecturer and nice tempo! TNx...E74Y
Glad that you liked it Muhamed 73
I bought one of those Ebay LC meters on the strength of what you show here but I can't achieve anything like the kind of accuracy that yours does. I've even tried measuring long pieces of 50ohm coax (M&P airborne 5) and the closest I could get was 60 ohm. I was as far off as 250ohms when measuring a short piece of RG58. I'd love to try this with something that might be a little more accurate and reliable one day.
Hm that sound odd. Normally this little LC metes are not rocket science so I wonder what's wrong..
TRX Bench yeah I'm going to try and do a few other tests over the weekend. I should be able to measure an inductor with my scope and signal generator and compare the impedance with a known resistor to get a ball park figure to compare it with.
danke fuer die super erklaerung. wie erklaert man das power handing von 450 Ohm ladder line und high power application?
kannst Du bitte eine video machen mit dem nanoVna als test geraet? merci
great video, is it possible to work out what mix ferrite rings are, I have a few and not sure what type they are...I did see a video once on how to check ferrite rings for certain applications..but that was long ago...thanks ! 73s
Thank you Cliff. Well the best is to measure the core material out. You get an idea on which frequency the material work and can decide if it fits into your project. In video #101 I show how an unknown ferrite can be tested... Hope that helps 73
Can we use an LCR meter for the test?
2) what'll happen if I use longer cable of say 10 metres without cutting a small piece?
Yes, to identify L and C. The calculation always stays the same regardless of the length of the coax......
Thanks Peter very informative cheers 73
Thank you James 73
Thank you for the video. Quite helpful!
Thanks for watching Sarath
very professional !
thank you for your very informative and enjoyable videos. i hope 2017 will be good for you, 73s
Thank you Mike Happy New Year 73
Please help one problem:
I bought a 50 ohm cable with velocity factor 82 and it does not work on the cb antenna. the capacity is the same 80pf / m but measured capacity at one end with the length of 10m it has double capacity compared to rg58
Very good video. Thanks!!!
Thank you Jim 73
very informative video. sir how to check connector impedance
Wonderful & I know now something thanks
how about smith chart can i use it for measuring the coaxial impedance?
You might also want to check the resistance, if its really high then you might have a bit of scope probe lead instead.
of course to make the test complete a resistance check can't be wrong. Thanks for watching, Dennis
Yes Thank you this video was of great importance to me, another wonderful small link in the secretes of the Universe hi hi
I have been lookin for this formula for a long time, this video is going to make learning so much more exciting, Sincere Thanks VK4JDJ
Hi Dennis, I'm glad the the video is of any use for you..Thanks for feed-back 73
Nano Henry! You wrote nF for the inductance value when you wrote them as as a sqrt! :) All good in the end. Just busting your chops a bit. 😅
well then, carry on
corks cable
joblessalex hi
I think it would be brittle ;) And the impedance would be extreme!
Corks cobble; get it straight; I still understood what he was saying
great explanation. I look forward to learning more. 73, ad0am
Thank you Adam 73
hello thank you for this video I would like to know which cable is used for measuring devices (oscilloscope, counter) is it possible to make them yourself thank you
Lab & test equipment with coaxial terminations almost always expects 50 ohm cable, with narrow exceptiions, such as specialized gear meant field use in the CATV industry.
In theory you could make your own coaxial cable, but would need precise and consistent control over its geometry (inside diameter of outer shield layer, outer diameter of center conductor, and dielectric constant of insulating material in between together determine impedance), also taking care to ensure good shield coverage to avoid leakage of RF, whether ingress or egress. Air-core coax can be assembled using two sizes of pipes nested within one another using spacers to keep them centered on the same axis, great for high power handling, but you then need a way to draw & keep moisture out.
How did you get the -9 and -12 in the equation?
terima kasih atas penjelasannya.
thank you
Thanks for watching 73
Erstmal ein gesundes erfolgreiches 2017, wieder mal ein tolles Video, ich muß jetzt auch mal meine Reste durchmessen.
Ich hab nur eine verständniss Frage, wie kommt die Einheit Ohm zustande wenn ich nH durch pF teile?
73 DO1BSW
Hall Bernd, vielen Dank und ein Frohes Neues Jahr! Ja das ist eine sehr gute Frage. Formeln enstehen immer durch Herleitung von sehr komplexen Zusammenhängen, so auch hier. Die Herangehensweise an das Thema geht über das Ersatzschaltbild einer Koaxleitung und die sich daraus ergebenden Differenzialgleichungen für U und I. Durch einsetzen und wegkürzen kommt man am Ende auf die vereinfachte Formel wie im Video dargestellt. Du merkst aber sicher schon über diesen Ansatz das sich dhinter komplexe Mathematik über die imaginären Inhate ergibt. Hoffe das hilft erst einmal...73
how do i set the velocity factor on coax using a mfj 259b ??
On twin antena CB set up, we use a RG-59 75ohm "Y" harness
Is it because we need to rise the impedance because we run parallel antenas? (Parallel mean half impedance of a single antena)
Hi Hugo, you are most likely talking about a quarter wave transformer set up.. Thanks for watching 73
TRX Bench no I mean co-phased fiberglass antenas or even 102" whips
I believe you both are correct in the answers. Yes it is because the impedance is a slight bit different but also this acts like a transformer to correct the impedance difference. That is what I understand about the "Y" harness setup. So you both answered the question but it also depends on the frequency and coax length. Coax is not 75 ohm the whole length. At a given frequency it is at certain lengths but that is a more complex way to look at it.
A dated video but still great. How about giving us an updated video on how to do the same thing with a nanoVNA as they are now cheap enough that anyone can afford one?
73, KD4LLC
Would a multimeter not work 🤔 measuring the legs of the cable and divide it to 1 cm and than multiply by 100 to get to the 1meter length and putting than the measured ohms in 🤔
Peter I suspect the open line might be influenced buy coupling to the bench items open line isn't shielded..
Maybe ?
Have a great 2017
You Are absolutely right. Thank you 73 HNY
"...zees meters are very sheep." "...and let's test ze cork's cable." Brilliant!
please pronounce the german name "büchholzer" . With ü, with ch, and z , hahahahahahahaha. Shame to me, if I laugh.
Excelente explicación
Thanks for watching 73
Example No have Calculator. How to write EXcel formula ?
I wonder why DC resistance doesn't factor in as well as inductance/capacitance.
I thought 300 ohm (ladder) twin lead type is better for receiving signals (lower loss), however interference is a problem with twin feed lines. Here's an interesting concept for HAM radio; Use different feed lines and antenna (30 ohm for TX and 75ohm for RX) Not practial but efficient. No body like standing waves that can cook you.
Twist it.