nanoVNA: Measuring the Frequency Response of an Amplifier Filter (068e)

In this video I will be showing you how to use your nanoVNA in stand alone mode to measure the frequency response of a VHF receive preamplifier that exists in my amplifier add on.
Included in this video are
* Set up the nanoVNA for a frequency response (through) measurement on an active device
* Proper VNA calibration
* Make the measurement results more readable by changing the REFERENCE POSITION and SCALE.
See below for the time markers ...
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=== PROMISED LINKS ===
======================
nanoVNA Official Site (so they claim)
nanorfe.com/na...
nanoVNA Manual (with menu map)
nanorfe.com/na...
Purchase nanoVNA V2 Plus 4 at
www.tindie.com...
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==== VIDEO LINKS =====
======================
VIDEO: VNA Foundations (first video in the series)
• VNA Introductions: Wha...
== THIS SERIES ==
VIDEO#1: nanoVNA: A Practical Menu Walk Through
• nanoVNA: A Practical M...
VIDEO#2: nanoVNA: Measuring the SWR of an Antenna
• nanoVNA: Measuring the...
VIDEO#3: nanoVNA: Measuring the Input Impedance of a Filter
• nanoVNA: Measuring the...
VIDEO#4: nanoVNA: Measuring the Frequency Response of a Filter
• nanoVNA: Measuring the...
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Time Markers for Your Convenience
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00:05 Introductory Comments
01:01 The Planning Phase
01:05 The Electrical Questions
02:17 1. D.C. Levels
03:10 2. The Amplifier's Maximum Input Level
05:14 3. The Amplifier's Anticipated Gain
06:05 4. The nanoVNA's Maximum Input for Channel 1
06:51 5. The nanoVNA's Stimulus Level from Channel 0
08:44 Bringing it together
09:27 Connectors & Adapters
09:58 The Connections for our Measurement
11:31 Measurement Methodology
11:37 WAY#1
13:35 WAY#2
15:13 Setting up the nanoVNA for the Measurement
17:04 nanoVNA Calibration
19:18 Making the Measurement
19:19 Final Preparations
19:24 Power Up!
19:45 Final Connections
20:43 Making the Measurement
20:56 Moving the Reference Position
22:09 Changing the Scale
22:41 The Measurement Results
23:55 Final Comments and Toodle-oots

[@cornbread-KO5RN]

👍👋 I AM SO GLAD TO HEAR SOMEONE MAKING A VIDEO WITH INSIGHT, thanks 👍.. 👋

[@eie_for_you]

Thanks, man! I am so happy that you were blessed by the video. You are very welcome. 🙂

[@W1RMD]

I'm late to make this comment, but you have a crystal ball! I've just rebuilt a stepped attenuator that I got at a hamfester 30 years ago, never used it because it had broken resistors in it from improper disassembly (by me?) and was wanting to see how to check it with my NanoVna. The NEXT DAY after getting it all back together you do a video on it! Thanks and 73!

[@eie_for_you]

WOW! Perfect timing! It'll be interesting to learn how well you did in rebuilding the attenuator. I am very glad the video was helpful. You are very welcome. 73's my friend. 🙂

[@RensePosthumus]

Veru lucid and usefull presentation, thanks!

[@eie_for_you]

Thank you! ... and you are welcome! I'm glad it was helpful. 🙂

[@user-em7lp1sb4k]

Thanks so much for the step by step setup process in making these measurement even though some steps are obvious others aren't. So many KZbin channels seem to skip this leaving the viewer pondering how the test setup was configured. Congrat's on 10k subscribers Ralph keep the videos coming.

[@eie_for_you]

You are very welcome, my friend. And what steps are obvious to some, aren't to others and visa-versa. If I include them all, then everyone is covered. Thanks for the congrats! I have quire a few more videos in queue and I am anxious to get to them. But the rest of life gets in the way. 🙂

[@arnoldgrubbs2005]

Very interesting video! Thanks!

[@eie_for_you]

You are very welcome! I am glad you liked it. 🙂

[@dennisqwertyuiop]

nice demo

[@eie_for_you]

Thanks! 🙂

[@MarcelGoedraad]

Dear Ralph Gable, First of all I would like to thank you for all the lessons in the RF domain, Too bad I didn,t have a teacher like you at school. Can you also explain how you can safely (hot) measure the RF power amplifier from 5 to 35W? How can you measure the input impedance of the RF amp (S11) and of course the gain of the RF amp (S21). I understand that you have to increase the output of the VNA to about 5W instead of 1mw (0 dbm) that comes out now. (and a high power attenuator after the RF amp). I own an Agilent ENA VNA, but I don,t dare to use it without a good explanation and so far I have only measured passive things. Regards, Marcel (from the Netherlands)

[@eie_for_you]

Now **THAT** is a good question! The problem we run into right out of the gate is amplifier drive. Like my little VHF amplifier will not switch into transmit mode until the input power reaches a certain level. So (just thinking out loud), I'd have to have an amplifier to bring the port 1 signal up to the required drive level of the target amplifier. Now comes the "fun" part ... calibration and measurement. I have a Bird inline wattmeter. It uses different plugins to configure it for frequency and power levels. It also has a plugin for an RF sampler which provides 50 dB of attenuation between the sampled power and the sample output. So, step 1 for me is to calibrate using all of this without the target amplifier in place. VNA Port1->Preamp->Bird->Dummy load. The -50 dB sampler output from the Bird-> VNA port 2. Calibrate as a through measurement. Remember, check the input level limitations of your VNA BEFORE doing anything. My Tektronix VNA is conservatively 0 dBm. According to the charts I have, +50 dBm is 100 Watts. So the output of my Bird sampler will be 0 dBm with 100 watts running through it to the dummy load. You *may* have to put an attenuator between the sampler output and VNA port 1 to make sure you are not exceeding the VNA's limits. Once everything is calibrated as a through measurement, then insert the target amplifier and make your through measurement as usual. Input impedance-wise ... for an amplifier like mine with the power sensitive transmit-receive switch, we can only measure the input impedance of the power amplifier if we can somehow trick it into thinking it needs to be in transmit mode. And don't forget to put a dummy load on the output of the amplifier. I hope this gives you some ideas. Always, always be careful. Attenuators are your friend to protect your VNA! 🙂

[@MarcelGoedraad]

Thank you for your detailed explanation. Fortunaly, I also have a Coaxial Dynamics 87015 Directional Coupler (-50db 50 to 500 mHz and a Bird 50 ohm line section with above components, a hot S11 measurements should be possible with 5W, right? So I never understood the proper setup and calibration. A video would certainly make many happy. I,m sure several people encounter this. Regards, Marcel

[@eie_for_you]

@@MarcelGoedraad The problem is the VNA has to see the input of the amplifier directly to properly do an S11 measurement. In my mind, I'd be thinking about taking the cover off and figuring out how to "manually" put the amplifier in transmit mode. I am hoping you have what you need at this point. As far as a video goes, I'd have to either create or buy a 5 watt preamplifier to do this. I have nothing "in house". Worth thinking about, though because it sounds like fun! 🙂

[@ornithopterindia]

👍Thank you sir.

[@eie_for_you]

You are very welcome! 🙂

[@NikiBretschneider]

In my opinion you don't need to go through Open/Short/Load calibration steps as these are related to the S11 (CH0 in nanoVNA language) and you have turned all S11 traces off (for a good reason, 1st port is connected to the attenuator, so S11 depends mostly on the attenuator itself, not the DUT, because that added -88dB on the S11 is far below the nanoVNA's noise floor). Calibrating Through (which is related to S21) only should be enough. It's nothing bad on going through the whole calibration process, it's just not necessary in this particular case.

[@eie_for_you]

This is very true and with my Tektronix VNA this is exactly what I do when doing through measurements only. With that said, this is the nanoVNA and it tends to want the whole enchilada even if it might not really apply. While it probably isn't technically needed, it never hurts to do it all. 🙂

[@carlosjsd4348]

Excelent thank you

[@eie_for_you]

Thank you and you are very welcome! 🙂

[@JanJeronimus]

Great and interesting demo! A question: Why is there the white kitchen cutting board below your circuit setup?

[@eie_for_you]

Thank you! Hopefully it will give you some ideas for future projects. You know, THAT is a good question about the cutting board. Admittedly, probably totally not necessary from an electrical perspective. But I like to be sure that there are no uncontrolled paths back to ground with my UUT and the blue mat that you see is a conductive mat connected to ground.🙂