9:1 UNUN Testing : Interesting Discoveries Using a NanoVNA
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- čas přidán 2. 04. 2024
- In this video we will a test a 9:1 UNUN at both the 50 ohm coaxial feedline point and the 450 Ohm antenna termination point with a NanoVNA. We will discover the UNUN's impedance, SWR and Return Loss from 1.8 Mhz to 30 Mhz.
My apologies for the camera being a bit off target in some of the scenes.
Thanks, I was always wondering if this kind of test could be done. I'm always leary about hooking an antenna matching network (tun er) because a tuner will "hide" a bad antenna. You can tune up a wet piece of spaghetti, but that doesn't mean that it's a good antenna. With THIS test you KNOW that it does indeed tune a 450 ohm load to 50 ohms PERIOD! You CAN'T tell that with an MFJ-259. Thanks for showing with no BS and 73! (Liked and subscribed)
Thank you for your detailed reply. You are so right! Everything can look rosey on the transmitter side of a tuner with what one may see as a "good match". But, what about the antenna side? lol
I built my own 9:1 unun a little while ago and it felt like magic. This demonstrates really well what it does. Thanks for sharing!
It really does...glad you enjoyed it! And, thank you for subscribing.
Ape sent me. Just subscribed. Great demonstration of both sides of the transformer. 73 OM
I am glad you liked it. And....Ape's the man! Learned a lot from his channel.
Nice work 👍
Thank you sir. Your video's are truly apprecated and inspiring!
Excellent informative video. Many thanks. 73..John..G4EIJ
Appreciate the comment. Glad you liked it John.
New Subscriber From Aberystwyth , Wales
Bless Up ❤
Thanks!
Nice video! May I suggest measuring your load with the VNA? The inductance you are seeing on the 50 ohm port might be caused by the long leads and spiral structure of the resistors... If they are somewhat inductive, then your transformer is actually pretty fine!
Great suggestion Rafael. Here is what I measured from the low inductive carbon resistor load. 1 Mhz 433 ohms -j2.0 ending at 30 Mhz with 433 ohms -j18.6
Good stuff. I would suggest you invest in either a phone holder or small tripod. Doing RF measurements with one hand lets the video down.
I couldn't agree with you more. I will take your suggestion to heart and see if I can improve my video's.
Hi, what is the purpose of this device called unun? Thanks
www.nextpcb.com/blog/what-is-an-unun-rf-antenna-unun#:~:text=An%20Unun%2C%20short%20for%20Unbalanced,suited%20for%20the%20transmission%20lines.
I already see a (big mistake) never use magnetic hardware! Bolts and screws must be made of stainless steel or brass. With a 450 Ohm resistor you always get a nice picture, now place the effective antenna wire on it and then look again, you will be surprised what it looks like.
Perhaps your right. I am planing on changing out the hardware using stainless steel. I then will see if there is any difference looking at the antenna with the VNA. Anyone else care to comment on this?
@@rfburns3472 Yes, I would suggest using brass hardware. 👍
@@rfburns3472well, here you’re checking the transformation ratio of 49. It is obvious that when you connect the wire (the real antenna) you’ll have different results. The complex impedance of the real antenna on its own installation will be all over the place and the transformer will transform (lower) that value closer to 50ohm for the radio or an antenna matching unit. (This was for the guy who commented first).
I have an antenna like this myself. 54 meters of wire starting from the roof, going up to a tree and then down to the end of the property. In my case on few bands I’m lucky to have already a good match, for the other bands where swr is little high I then use the “tuner”.
Otherwise one could buy a remote antenna tuner, place it outside and start the random lenght of wire out of it. This way it’ll adapt the LC network to give you always the best matching transformer at the antenna point.
73
Diego