Ciao Ralph, ottima spiegazione, nella realtà hai misurato il valore di SWR che comprende anche la linea di trasmissione (il cavo coassiale) quindi il reale valore di SWR al connettore dell'antenna sarà un po' piu alto di quello che hai misurato, questo è dovuto all'attenuazione del cavo, che riduce l'ampiezza del segnale riflesso! Comunque ottimo video, ti seguo sempre con attenzione 👏👏👏👏👏
Thank you! The point of this video was aimed the "How to use the nanoVNA to measure SWR." You are very correct regarding the SWR at the end of a transmission line. With that said, the effect of the attenuation of the cable depends entirely on the frequency in use and the particular feedline being used. At lower frequencies, the effect is generally so minimal so as to be ignored. When we get up into frequencies above 50 MHz, however, we now have to start doing our accounting. With knowledge of the feedline being used and its characteristics, we can measure the SWR at the end of the feedline and then correct for feedline loss to get a more accurate sense of the SWR. Not perfect, but better. Unfortunately, it is rarely possible to measure the SWR (or impedance) of an antenna at its feed point. 🙂
@@eie_for_you ciao Ralph, hai perfettamente ragione, mi era sfuggito che siamo solo a 7MHz, e quindi l'effetto del cavo e trascurabile. Scusami ma sono abituato a ragionare su frequenze più alte, dove l'attenuazione del cavo può essere anche di 2 o 3dB e quindi bisogna tenerne conto! Ad esempio già in VHF 2m il "SWR Masking effect" dovuto all'attenuazione del coassiale può essere importante, non parliamo della banda UHF che già a 440MHz può diventare impossibile misurare l'SWR con un semplice rosmetro, (che leggerà SEMPRE valori molto piu bassi di quelli effettivi al connettore dell'antenna) in alcuni casi è possibile che non vi siano differenze di SWR sia che l'antenna sia collegata, sia che sia guasta o assente, perché l'attenuazione del cavo se elevata (ma nemmeno molto) rende la misura come se si stesse misurando un carico fittizio! (Dummy load) quindi mi domando a cosa servano i Rosmetri (SWR meter) per le bande UHF se segnano sempre 1:1🤣🤣🤣 Sei veramente preparato👏👏 te lo dico io che ho 30 anni di esperienza sulle antenne. Un caro saluto
@@pierfrancescograzioli4080 I have visited this whole topic personally, realizing that SWR meters and adapters and ... well just about anything we insert in the feedline also inserts their own issues. Our "beloved" UHF connectors (PL-259/SO-239) for instance at frequencies exceeding 100 MHz... th-cam.com/video/HjbUK7yjpjA/w-d-xo.html or the antenna switch or SWR meter ... th-cam.com/video/1fpoViuxn3c/w-d-xo.html All of this motivated me to completely redo my VHF/UHF antenna system. Everything is N-type connectors. There are no antenna switches. The only thing in line is my lightning arrestor (with N connectors) and I tested it with my VNA before I used it. In my mind, the average, affordable SWR meter is pretty much useless and VHF and UHF frequencies. 🙂
Great video! It helps to show a few of the things that are not obvious but are lurking in the settings, which makes using this device a lot nicer. And it always helps to know the reasoning behind some of the controls.
Great video. It also a good idea to quickly short out the antenna terminals before hooking them to the VNA to bleed off any static. I've heard about people damaging their VNA from that. Dipoles are static and lightening magnets due to the fact that they are an open circuit to dc. Discones and fiberglass antennas are also really bad. Take care and 73!
I **KNEW** I was forgetting SOMETHING! 😕Something was just nagging at me the whole time I was putting this together ... and THIS was it! Thank you for telling me. I put a HUGE ***CAUTION*** in the description.🙂
@@eie_for_you Thanks! Also, I assume this is a 2.8 inch screen VNA you're using (like mine). Either way this video will be HUGE in me first using mine. I've got some female SMA to male BNC adapters, so if I can, I believe I'm going to "permanently" leave them in place. I also have female SMA to female BNC adapters to hook the calibration standards. I think surface mount resistors can be soldered inside on connectors to make cheap calibration standards, particularly at lower frequencies. 73!
@@W1RMD I bought some male SMA to female SMA adapters which "live" on my nanoVNA. If I wear out the adapter, then I just replace it. This is a LOT better than wearing out the connectors on the VNA itself! Don't forget, when calibrating the nanoVNA, you need to do it as close to the place where you connect the thing to be tested as possible. If you are measuring impedance, then you would possibly apply a "port extension" (AKA: electrical delay" in the nanoVNA world). Failure to do all of this *will* lead to misleading readings. 🙂
@@eie_for_you Great! I heard you mention port extension before and in this video. Which video is best to watch how to do that? I have not seen all of your VNA videos yet.
@@W1RMD Of the released videos ... there is this one on measuring impedance: th-cam.com/video/Pti8Erw_Kkg/w-d-xo.html I use the computer interface to do it in this one. On the other hand (she wore a glove ... LOL 😀), my most recent video on measuring the input impedance of a filter using a nanoVNA in "stand-alone" mode will be released to the public on May 15th. This followed by measuring the frequency response of the same filter two weeks later. Then the frequency response of an amplifier. 🙂
Dear Ralph, thanks for walking through this process as this is exactly what I bought my NanoVNA for. 🙂 My model has SMA connectors and came with calibration pieces for SMA, of course, whereas my T2LT antenna that I would like to tune has a UHF connector and I need to use an adapter (SMA/UHF). Am I getting this right that for this type of measurement, I mean for merely finding the SWR minimum while tuning the antenna, I do not necessarily need to buy UHF calibration pieces to plug them into the adapter, but instead I can using the SMA calibration and I can neglect the hopefully minimal inaccuracy due to not optimal calibration? I assume the inaccuracy will be merely regarding the absolute values of the SWR, but it will not impact the position of the SWR minimum whithin the band, right?🤔 73 Henner, DO1HNR
Good day Henner! If all you are doing is measuring the SWR of an antenna and you are using a *good quality* adapter, then calibrating the nanoVNA at the SMA connector and adding the adapter to measure your antenna which sports the UHF connector will be just fine. As a side note,while we are all very accustomed to thinking in terms of SWR, if you are interested in the most precise way of seeing the exact frequency of resonance, then view it in terms of return loss (S11 with a dB format). The translation from return loss to SWR smooths out the curve so that the exact resonant frequency becomes harder to see. In the end, however, we both love to see the SWR because this is how we are accustomed to thinking about antenna matching. I mean, we all know that an SWR of 1.02:1 is a good thing, but a return loss of -17 dB doesn't really mean anything to us (though they are the same thing). 🙂
This guy knows his stuff!
Thanks! 🙂
Ciao Ralph, ottima spiegazione, nella realtà hai misurato il valore di SWR che comprende anche la linea di trasmissione (il cavo coassiale) quindi il reale valore di SWR al connettore dell'antenna sarà un po' piu alto di quello che hai misurato, questo è dovuto all'attenuazione del cavo, che riduce l'ampiezza del segnale riflesso! Comunque ottimo video, ti seguo sempre con attenzione 👏👏👏👏👏
Thank you! The point of this video was aimed the "How to use the nanoVNA to measure SWR."
You are very correct regarding the SWR at the end of a transmission line.
With that said, the effect of the attenuation of the cable depends entirely on the frequency in use and the particular feedline being used. At lower frequencies, the effect is generally so minimal so as to be ignored. When we get up into frequencies above 50 MHz, however, we now have to start doing our accounting. With knowledge of the feedline being used and its characteristics, we can measure the SWR at the end of the feedline and then correct for feedline loss to get a more accurate sense of the SWR. Not perfect, but better. Unfortunately, it is rarely possible to measure the SWR (or impedance) of an antenna at its feed point.
🙂
@@eie_for_you ciao Ralph, hai perfettamente ragione, mi era sfuggito che siamo solo a 7MHz, e quindi l'effetto del cavo e trascurabile. Scusami ma sono abituato a ragionare su frequenze più alte, dove l'attenuazione del cavo può essere anche di 2 o 3dB e quindi bisogna tenerne conto! Ad esempio già in VHF 2m il "SWR Masking effect" dovuto all'attenuazione del coassiale può essere importante, non parliamo della banda UHF che già a 440MHz può diventare impossibile misurare l'SWR con un semplice rosmetro, (che leggerà SEMPRE valori molto piu bassi di quelli effettivi al connettore dell'antenna) in alcuni casi è possibile che non vi siano differenze di SWR sia che l'antenna sia collegata, sia che sia guasta o assente, perché l'attenuazione del cavo se elevata (ma nemmeno molto) rende la misura come se si stesse misurando un carico fittizio! (Dummy load) quindi mi domando a cosa servano i Rosmetri (SWR meter) per le bande UHF se segnano sempre 1:1🤣🤣🤣 Sei veramente preparato👏👏 te lo dico io che ho 30 anni di esperienza sulle antenne. Un caro saluto
@@pierfrancescograzioli4080 I have visited this whole topic personally, realizing that SWR meters and adapters and ... well just about anything we insert in the feedline also inserts their own issues. Our "beloved" UHF connectors (PL-259/SO-239) for instance at frequencies exceeding 100 MHz...
th-cam.com/video/HjbUK7yjpjA/w-d-xo.html
or the antenna switch or SWR meter ...
th-cam.com/video/1fpoViuxn3c/w-d-xo.html
All of this motivated me to completely redo my VHF/UHF antenna system. Everything is N-type connectors. There are no antenna switches. The only thing in line is my lightning arrestor (with N connectors) and I tested it with my VNA before I used it.
In my mind, the average, affordable SWR meter is pretty much useless and VHF and UHF frequencies. 🙂
Great video! It helps to show a few of the things that are not obvious but are lurking in the settings, which makes using this device a lot nicer. And it always helps to know the reasoning behind some of the controls.
Thanks! 🙂
Great series.
Thanks, man! I am so glad you have been blessed by it! 🙂
I love the Nano VNA. Good lesson
Thank you! 🙂
Great video. It also a good idea to quickly short out the antenna terminals before hooking them to the VNA to bleed off any static. I've heard about people damaging their VNA from that. Dipoles are static and lightening magnets due to the fact that they are an open circuit to dc. Discones and fiberglass antennas are also really bad. Take care and 73!
I **KNEW** I was forgetting SOMETHING! 😕Something was just nagging at me the whole time I was putting this together ... and THIS was it! Thank you for telling me.
I put a HUGE ***CAUTION*** in the description.🙂
@@eie_for_you Thanks! Also, I assume this is a 2.8 inch screen VNA you're using (like mine). Either way this video will be HUGE in me first using mine. I've got some female SMA to male BNC adapters, so if I can, I believe I'm going to "permanently" leave them in place. I also have female SMA to female BNC adapters to hook the calibration standards. I think surface mount resistors can be soldered inside on connectors to make cheap calibration standards, particularly at lower frequencies. 73!
@@W1RMD I bought some male SMA to female SMA adapters which "live" on my nanoVNA. If I wear out the adapter, then I just replace it. This is a LOT better than wearing out the connectors on the VNA itself!
Don't forget, when calibrating the nanoVNA, you need to do it as close to the place where you connect the thing to be tested as possible. If you are measuring impedance, then you would possibly apply a "port extension" (AKA: electrical delay" in the nanoVNA world). Failure to do all of this *will* lead to misleading readings. 🙂
@@eie_for_you Great! I heard you mention port extension before and in this video. Which video is best to watch how to do that? I have not seen all of your VNA videos yet.
@@W1RMD Of the released videos ... there is this one on measuring impedance:
th-cam.com/video/Pti8Erw_Kkg/w-d-xo.html
I use the computer interface to do it in this one.
On the other hand (she wore a glove ... LOL 😀), my most recent video on measuring the input impedance of a filter using a nanoVNA in "stand-alone" mode will be released to the public on May 15th. This followed by measuring the frequency response of the same filter two weeks later. Then the frequency response of an amplifier. 🙂
Dear Ralph, thanks for walking through this process as this is exactly what I bought my NanoVNA for. 🙂
My model has SMA connectors and came with calibration pieces for SMA, of course, whereas my T2LT antenna that I would like to tune has a UHF connector and I need to use an adapter (SMA/UHF).
Am I getting this right that for this type of measurement, I mean for merely finding the SWR minimum while tuning the antenna, I do not necessarily need to buy UHF calibration pieces to plug them into the adapter, but instead I can using the SMA calibration and I can neglect the hopefully minimal inaccuracy due to not optimal calibration? I assume the inaccuracy will be merely regarding the absolute values of the SWR, but it will not impact the position of the SWR minimum whithin the band, right?🤔
73
Henner, DO1HNR
Good day Henner! If all you are doing is measuring the SWR of an antenna and you are using a *good quality* adapter, then calibrating the nanoVNA at the SMA connector and adding the adapter to measure your antenna which sports the UHF connector will be just fine.
As a side note,while we are all very accustomed to thinking in terms of SWR, if you are interested in the most precise way of seeing the exact frequency of resonance, then view it in terms of return loss (S11 with a dB format). The translation from return loss to SWR smooths out the curve so that the exact resonant frequency becomes harder to see.
In the end, however, we both love to see the SWR because this is how we are accustomed to thinking about antenna matching. I mean, we all know that an SWR of 1.02:1 is a good thing, but a return loss of -17 dB doesn't really mean anything to us (though they are the same thing). 🙂
Great video as usual.
Thanks, man! 🙂
👍Thank you sir.
You are welcome! 🙂