Great video. Thanks for the deep dive. Very much enjoyed this. I wish we had tools like the Nano VNA when I was in engineering school, a million years ago. I can recall doing double stub tuning on a waveguide using paper Smith charts. What an experience!
Thanks! You are very welcome! 🙂 I am so glad that we have these tools at our fingertips, too. Unfortunately, as you saw in the video, these less expensive VNAs DO have their limitations. 😞 But, for the average person doing stuff, they do a LOT for a little ($$$). 🙂
Out of curiosity how does the amplifier switch RX/TX, relay or diode switching? I have found most cheap amplifiers use relay switching and usually use relays that are not suitable for higher frequency. That and just flat out poor design results in input/output impedance that can be all over the map. Better amplifiers like my Linear Amp - Gemini series and commercial TPL amplifiers use PIN diode switching . Mike KC3OSD
@@mikesradiorepair You question made me look….yep! There are two relays under the hood. AND I discovered that there is a switch that is labeled “FM” “SSB” that I didn’t know existed. You are right, based on the time in my life that I bought this, it is more than likely an inexpensive device.😀
@@eie_for_you Well that's a strange place to stick the FM/SSB switch. I can just hear that QSO now. "Hold on George, I have to dismantle my amplifier so I can switch into SSB mode".
If you have a circulator that operates at that frequency range you can connect the stimulus signal with an attenuator to port 1 of the circulator, your amplifier at port 2 and the port 3 of the circulator to receive port of your VNA and you are left with a S21 measurement that only passes once from the attenuator. Of course calibration is needed.
Great Video. Thank you very much. It’s a pity, we technically can’t reproduce your results with our humble nano VNAs… But, as we all guessed, there must be some reasons why more expensive gear exists 😅.
Hi Ralph, again a very good tutorial! One easy (?) wish. Imagine a simple FM transmitter with a simple C-class BJT stage in the output, how to find the matching network for the antenna???
Hmmmm ... interesting thought. Of course, to do this you would need to know the complex output impedance of the class-C amplifier first. Then you get to work with a Smith Chart. Sounds like and interesting project. 🙂
I have a few videos on tuning duplexers (here is the link to the first video: ua-cam.com/video/ZZHknVp3asc/v-deo.html). So, the answer to your question is not really, but also sort of. It has the functionality but not the dynamic range. It can easily do the Return Loss portion of the tuning. But the reject frequency is where it cannot quite cut it. The reject dip will be a flat and wide bottomed dip with no way to really know what the exact reject frequency is. This is where the dynamic range issue kicks in. Part of this is due to the fact that the stimulus level is lower (mine is a fixed -9 dB!). The other part of it is the limitations of the "front end" of the receive port (port 2 - nanoVNA speak = port 1). With all of that said, it is a great way to practice tuning a duplexer! If you are willing to accept a just "OK" tune, then it might do what you want. 🙂
I've been keenly watching your videos on measuring input impedance and frequency response. The importance of the design and planning is what struck me most. I have a quesiton that hopefully can help with my electronics knowledge gap. I have heard that impedance matching is not as important for RX, perhaps since the power levels are extremely low (if you think about the antenna as transmitting into the receiver and the levels are microvolts). According to a Rohde and Schwarz video on VSWR, at around 8:1, 60% of power is reflected and therefore perhaps this would be a 'missed opportunity' to maximise the received signal? However, I have also heard about impedance bridging where it is important for the load Z (amplifier in this case) to be much higher (ideally by a few orders of magnitude) than the source (antenna in this case), to maximise voltage transfer. Could the amplifier receive circuitry benefit more from a higher voltage transfer than power transfer from the antenna? Is my understanding correct and could this be the reason for why on the RX side of this amplifier the Z is higher? It feels like there is a lot of conflicting info in my head....
@@Alex-M0OOV well, admittedly, I am not a receiver designer. My personal thinking is that there is a trade off going on here. One comment mentioned that a receiver from end was also adjusted for noise figure, not impedance matching. Nonetheless … power reflected due to an impedance mismatch … 60% of it … it doesn’t seem to be power that can induce voltage across a load if it never gets there (it’s been reflected 🥺). So, I am not sure how to address this. In my mind it should be at lease **close** to the system impedance of 50 Ohms.🙃
I am at a bit of a loss as to what you are trying to measure. Are you measuring the input impedance of your tinySA whose input limits are 1.5 V pk-pk? As a point of reference, 0dBm is 1 mW into a 50 Ohm load = 50 mV RMS = 141.4 mV p-p. Your 1.5V p-p = 530 mV RMS => 5.6 mW into a 50 Ohm load => 7.5 dBm. My nanoVNA output is below 0 dBm. :-)
@eie_for_you I want to know if I can directly connect output of nano VNA to tiny SA . Also what are limit of tiny SA.. Plz can u confirm..I just dont want to blow my tinysa
@@minazulkhan8287 Here is the LINK to the complete specifications for the tinySA: tinysa.org/wiki/pmwiki.php?n=Main.Specification Therein it states: "Absolute maximum input level of +10dBm with 0dB internal attenuation " Your nanoVNA max output is 0dBm (theoretically - but it is actually likely less than that). So, it looks like you are quite safe. 🙂
Is all that noise coming from the probe or from your environment or both? Maybe you should try it again in a different location where you aren’t surrounded by electronics that might be giving off parasitic EMF?
Yes, all of this noise is coming from the nanoVNA. It is the noise associated with the front end of the nanoVNA itself (every circuit has noise of some sort). 🙂
@@steelinhank I can see the the importance of the noise figure, but, from my perspective…how much of the signal is reflected back at the antenna because of the impedance mismatch. There must be a balance. Of course, this is also an **inexpensive** and **OLD** preamp, too. 😀
Great video. Thanks for the deep dive. Very much enjoyed this. I wish we had tools like the Nano VNA when I was in engineering school, a million years ago. I can recall doing double stub tuning on a waveguide using paper Smith charts. What an experience!
Thanks! You are very welcome! 🙂
I am so glad that we have these tools at our fingertips, too. Unfortunately, as you saw in the video, these less expensive VNAs DO have their limitations. 😞 But, for the average person doing stuff, they do a LOT for a little ($$$). 🙂
Great Video. Thank you.
@@jluke6861 Thank you! … and you are very welcome! 😀
👍Thank you sir.
@@ornithopterindia You are welcome!😁
Out of curiosity how does the amplifier switch RX/TX, relay or diode switching? I have found most cheap amplifiers use relay switching and usually use relays that are not suitable for higher frequency. That and just flat out poor design results in input/output impedance that can be all over the map. Better amplifiers like my Linear Amp - Gemini series and commercial TPL amplifiers use PIN diode switching . Mike KC3OSD
@@mikesradiorepair You question made me look….yep! There are two relays under the hood. AND I discovered that there is a switch that is labeled “FM” “SSB” that I didn’t know existed. You are right, based on the time in my life that I bought this, it is more than likely an inexpensive device.😀
@@eie_for_you Well that's a strange place to stick the FM/SSB switch. I can just hear that QSO now. "Hold on George, I have to dismantle my amplifier so I can switch into SSB mode".
@@mikesradiorepair 🤣🤣🤣🤣
If you have a circulator that operates at that frequency range you can connect the stimulus signal with an attenuator to port 1 of the circulator, your amplifier at port 2 and the port 3 of the circulator to receive port of your VNA and you are left with a S21 measurement that only passes once from the attenuator. Of course calibration is needed.
Interesting idea.😁 Unfortunately, I do not have one of those things. 😞
Great Video. Thank you very much. It’s a pity, we technically can’t reproduce your results with our humble nano VNAs… But, as we all guessed, there must be some reasons why more expensive gear exists 😅.
@@pasixty6510 Thanks! … and you are welcome!
I ***really*** wanted to be able to do it with the nanoVNA. I, like you, were quite disappointed.😁
Hi Ralph, again a very good tutorial! One easy (?) wish. Imagine a simple FM transmitter with a simple C-class BJT stage in the output, how to find the matching network for the antenna???
Hmmmm ... interesting thought. Of course, to do this you would need to know the complex output impedance of the class-C amplifier first. Then you get to work with a Smith Chart. Sounds like and interesting project. 🙂
Thanks for some very good and helpful videos.
Can you and if so how would you use a nanovna to set up a set of duplexer cans for repeater use?
I have a few videos on tuning duplexers (here is the link to the first video: ua-cam.com/video/ZZHknVp3asc/v-deo.html).
So, the answer to your question is not really, but also sort of. It has the functionality but not the dynamic range. It can easily do the Return Loss portion of the tuning. But the reject frequency is where it cannot quite cut it. The reject dip will be a flat and wide bottomed dip with no way to really know what the exact reject frequency is. This is where the dynamic range issue kicks in. Part of this is due to the fact that the stimulus level is lower (mine is a fixed -9 dB!). The other part of it is the limitations of the "front end" of the receive port (port 2 - nanoVNA speak = port 1).
With all of that said, it is a great way to practice tuning a duplexer!
If you are willing to accept a just "OK" tune, then it might do what you want. 🙂
@@eie_for_you Thanks. I'll have to check those videos out.
Have a great holiday season.
@@REKlaus And to you, too! 🙂
I've been keenly watching your videos on measuring input impedance and frequency response. The importance of the design and planning is what struck me most. I have a quesiton that hopefully can help with my electronics knowledge gap. I have heard that impedance matching is not as important for RX, perhaps since the power levels are extremely low (if you think about the antenna as transmitting into the receiver and the levels are microvolts). According to a Rohde and Schwarz video on VSWR, at around 8:1, 60% of power is reflected and therefore perhaps this would be a 'missed opportunity' to maximise the received signal? However, I have also heard about impedance bridging where it is important for the load Z (amplifier in this case) to be much higher (ideally by a few orders of magnitude) than the source (antenna in this case), to maximise voltage transfer. Could the amplifier receive circuitry benefit more from a higher voltage transfer than power transfer from the antenna? Is my understanding correct and could this be the reason for why on the RX side of this amplifier the Z is higher? It feels like there is a lot of conflicting info in my head....
@@Alex-M0OOV well, admittedly, I am not a receiver designer. My personal thinking is that there is a trade off going on here. One comment mentioned that a receiver from end was also adjusted for noise figure, not impedance matching.
Nonetheless … power reflected due to an impedance mismatch … 60% of it … it doesn’t seem to be power that can induce voltage across a load if it never gets there (it’s been reflected 🥺).
So, I am not sure how to address this. In my mind it should be at lease **close** to the system impedance of 50 Ohms.🙃
I wonder if the amp input was using a 9pf cap to gnd, what the loss would look like?
Part of the issue, it looks like, is the fact that they use electromechanical relays for the T-R switch. 🙂
Hi.. EIE ... Can I give output of nano VNA ( 1 mhz square wave, 1.5 V Peak to Peak at the input of tiny SA. Or there is need of attenuator (value)?
I am at a bit of a loss as to what you are trying to measure. Are you measuring the input impedance of your tinySA whose input limits are 1.5 V pk-pk?
As a point of reference, 0dBm is 1 mW into a 50 Ohm load = 50 mV RMS = 141.4 mV p-p.
Your 1.5V p-p = 530 mV RMS => 5.6 mW into a 50 Ohm load => 7.5 dBm.
My nanoVNA output is below 0 dBm. :-)
@eie_for_you I want to know if I can directly connect output of nano VNA to tiny SA . Also what are limit of tiny SA.. Plz can u confirm..I just dont want to blow my tinysa
@@minazulkhan8287 Here is the LINK to the complete specifications for the tinySA:
tinysa.org/wiki/pmwiki.php?n=Main.Specification
Therein it states: "Absolute maximum input level of +10dBm with 0dB internal attenuation "
Your nanoVNA max output is 0dBm (theoretically - but it is actually likely less than that).
So, it looks like you are quite safe. 🙂
Thanks......it worked 😊.
@@minazulkhan8287 You are very welcome! 🙂
Is all that noise coming from the probe or from your environment or both? Maybe you should try it again in a different location where you aren’t surrounded by electronics that might be giving off parasitic EMF?
Yes, all of this noise is coming from the nanoVNA. It is the noise associated with the front end of the nanoVNA itself (every circuit has noise of some sort). 🙂
The high VSWR doesn't surprise me. The preamp is adjust for lowest noise figure not VSWR
@@steelinhank I can see the the importance of the noise figure, but, from my perspective…how much of the signal is reflected back at the antenna because of the impedance mismatch. There must be a balance. Of course, this is also an **inexpensive** and **OLD** preamp, too. 😀
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@@dennislynch1326 I just checked…I have replied to every comment that is visible to me.