It is far better to make a direct VNA port connection to the resonator or circuit. This will allow accurate measurement of impedance, resonant frequency and Q factor. Using a grid drip meter is less accurate because the unknown coupling factor does not allow the measurement of impedance or quality factor. Grid drip meters were developed in the days before VNA test instruments were available.
In the future use painters tape and make a square on the table or floor marking the border of your video shot area. This way it will help you not to do things outside the border where most of your work is not seen by the viewer.
Mine came with such a small manual, I am not even sure what all functions it has, I have just been trying to test some GMRS antennas with it. After watching this video, I see that I need to find instructions on how to calibrate it properly.
Interesting. I was first licensed in '57 so am familiar with GDOs. actually I started collecting them at hamfests and have MFJ, Heath, Kenwood and Simpson ones. (I'd like to get an Eico with a real vacuum tube in it.). Anyway I also have a Nano and your demo was very interesting. But all my GDOs have a series of plug-in coils with many more turns and I wondered what difference that made compare to your little homebrew one. Is it because of the wideband sensitivity of the Nano? Does Q enter into it? 73
This idea came from a magazine article years ago. MFJ copied it and sold it as an adaptor for their antenna analyzers. It is actually better just to connect the trap or resonant circuit to the VNA directly and measure the impedance of the trap or resonant circuit. Just use a short jumper with a cable separation at the far end with alligator clips. Calibrate that with an OSL calibration. The VNA can measure the actual trap impedance and Q using a direct connection, I do it every week for testing RF chokes. You don't have to spend $53 for a useless hunk of wire you can find in your junk box. You can make a jumper or adaptor for a jumper with clip leads and read the actual impedance with a direct connection. It can do anything this can do and better, and you save almost $60!!
I have tried measuring directly from the S11 port, for some reason the nano shows them a few hundred KHz low on frequency. Might be an error on my part.
You should get some connector savers. They look like an attenuator but they have a straight through connection. Just wind them onto the two VNA ports and leave them there. No need to use jumpers that way.
was going to recommend this myself. I went the extra step of 3D printing a little attachment that slips over the hex nuts of the SMA-savers to keep them from turning
That $53.95 ad for a set of pick-up loops for an MFJ cracked me up! That's as much as an entire NanoVNA. Thanks for the videos. Some good hams, including you are turning into RU-vid Elmers and creating a body of work that can teach hams of any level how to build, how to repair, how to design, even everything about atmospherics, or tips and tricks. And the info just grows continually. It's a wonderful thing. Now, if we could just get rid of some of the Baofeng unboxing videos. :) Thank you.
Hey now! Those CCRs are getting lots of new blood into radio, and a bunch of us old dogs back into radio. Studying for my tech ticket currently. Without a Baofeng UV-5R and a GMRS-9R, I certainly would not have been able to afford to get started again.
@@javabeanz8549, you'll need to spell out what a CCR is. I've found hundreds of definitions, from constant current regulators to Credence Clearwater Revival.
@@javabeanz8549, I have nothing at all against the cheap radios, unless they have illegal harmonic output. I have 6 or 8 of them. What I've grown weary of is video after video of kids who know essentially nothing about radio simply opening up the boxes and talking about doing just that. I already know how to open boxes. I've seen far too many such videos as I was trying to learn about the actual characteristics of the radios. They waste everyone's time. It takes a while to sort through the garbage channels to find channels like this one with actual content.
@@johnwest7993 oh yes, the Wannabes... they want to be influencers, so they bought a $25 to $60 radio on Amazon, Temu, etc, and opened the box and read through the tiny manual that comes with most of them, played with the radio for a few minutes and think that they are experts. I think that we can find their kind in many areas. I have a collection here, Bao Feng, Tidradio, B-Tech, QYT, Radioddity. In fact, there's supposed to be another radio on UPS today. And no, I won't be doing an unboxing video ;0) I was into CBs and Shortwave listening 40 years ago or so. Now I am more into GMRD, and want to get my technician ticket so I can get on UHF and VHF. I really don't have enough property to get into HF, and besides that, I can deal with all the noise coming in on skip, it just gives me a headache anymore.
I wound mine around a 1.25" pill bottle and put the SMA connector directly to the two inch long wires. (no coax) If I can connect it, I can replace it. I used "liquid tape" to bind the two turns and the two inch long lead into a rod. I used about #20 enameled wire. I use mine like a wand holding the MiniVNA-Pro with coil as a hand held probe. (no vise) Ron W4BIN
love how he corrected when he had 1 to many turns/windings, new to the RF Field and learning as much as i can as i find it all interesting and would love to play with some setups later on when i have the capital.
What this wont replicate is the very high impedance the grid dip meter operated at(meg ohms) because you are now coupling into a 50ohm test system. This means the circuit under test will be loaded and damped much more than with the GDM. What this might mean in practical terms is hard to say, in use the circuit might react at slightly different frequency to that measured with the Tiny VNA. The tank circuit in that regen receiver might not have the Q you were expecting! :)
Not quite. The coupling coefficient between coils will allow an impedance match as seen between the low and high frequency trap measurements, the coupling increases as the frequency rises, increasing loading. Not ideal but it will give a good indication. A real GDO still reigns supreme.
If I have time, I may try NanoVNA vs GDO later. I found that I can very accurately measure the dip frequency on a GDO by zero beating the GDO with a calibrated receiver. It would be interesting to see if there any difference between the Nano and the GDO.
@@Steve-GM0HUU that would be good if you could. The poster did a good and detailed job at the construction of it, but left it a bit thin on the use-cases side.. I hope he would consider doing a Part 2.. Thanx-n-73 lm-VK3OLA
@@lmantuano6986 I did a quick test. I used my old TRIO DM-801 to get a dip on a 12m trap. My receiver indicated dip frequency of 25.253MHz. I used my NanoVNA v2.2 to get a dip on on the same trap and the same receiver indicated a dip frequency of 25.525MHz. OK, not a very accurate test but it did indicate a GDO vs NanoVNA difference of 272KHz. Assuming one of the methods is accurate, 272KHz is a approx. a 1% error.
Hi Rick, i am trying to test a Key Fob, RF type for central locking on car, i am told it can be done with a nano VNA, but i haven't managred to do it yet...Fred in Uk.
Probably better to use a rtl-sdr for quick "does it transmit" when you have a rough idea of the frequency. (You're only going to get 2mhz instantaneous bandwidth, but you can check various bands quickly)
If your scope is high enough frequency, you can put a loop on the end of an oscilloscope probe and hold it to the case of the Fob and see if it is transmitting RF.
Great mod! I've got a couple of these mics branded as Johnson for my old CB radios. Haven't tried them in years. If the elements are bad, now i have a way to mod them. 73!
