nanoVNA - Measuring Antenna & Coax Characteristics (Revised Feb 16, 2024)

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Пікірлер: 26

@aerofart 2 ай бұрын

Gregg, I’ve been subscribed to your channel for probably over a year now and am just now starting to watch (and understand) more of your videos. I just want to thank you for all the meticulous work you do and the effort you put into understanding such interesting areas of the hobby. The information you provide with your practical and thought experiments is very interesting and useful. You are a hardcore amateur in every sense of the word. Thanks again!

@ve6wo 2 ай бұрын

Thank you.

@Ratchet2 5 ай бұрын

I like these types of experiments. This is what drew me to amateur radio back in 1995. Great video.

@danl3547 11 ай бұрын

Your metallic mast may be interfering with your setup. Generally, a dipole is mounted with non-metallic (dacron etc.) lines or a fiberglass pole.

@ve6wo 11 ай бұрын

Yes, the metal pole will likely have some effect. Also the metal roofing on my garage, and a host of other things unique to my location, all of these things will change how the antenna behaves. For most of us, we cannot control these environmental factors so we should be able to measure and tune and impedance match for each specific location.

@ReefMimic 6 ай бұрын

Don’t worry you’re not the only one. I Cleaned my work table in the garage only to clutter it back up again.

@darylcheshire1618 7 ай бұрын

I have 20m of RG-213 which sat on the floor of my garage for 20 odd years. It seems to be working normally but I’ve since got some RG-58. I have ordered my nanoVNA and will look forward to check if this cable has any loss. At the moment it seems neglible.

@jampskan5690 2 ай бұрын

You sound less Canadian in the revision of this video. Also, I have that same keyboard, and it is a beast.

@patrickdemeyer2210 11 ай бұрын

If you change the stimulus , you should recalibrate ... every time.

@R50_J0 11 ай бұрын

True that.

@ve6wo 11 ай бұрын

I have done this experiment.. at these low frequencies I observed no benefit. The readings were the same. If a person goes outside of the range of frequencies that were used to calibrate the nanoVNA, then yes, I will re-calibrate.

@WarrenPostma 2 ай бұрын

@@ve6wo I'm brand new to the nanovna and I've noticed that recalibrating 80x won't make my results repeatable until I also get a work holding hands free situation, as moving my HANDS around the antenna and the analyzer moves things. :-)

@ve6wo 2 ай бұрын

@WarrenPostma yes, my aluminum housed nanoVNA-F is quite bad for that. One way to take measurements without your hands touching is to hook it up to your computer and to use nanoVNA Saver software to control it.

@mjktrash 5 ай бұрын

To be fair, much of this is over my head, but one thing did stick out to me as I was watching, the change in resonance was ~.02Mhz on the 80m band, correct? So is what amounts to about a 4% change, right in the middle of the band practically significant? Or was this just an academic exercise? (Which is fine BTW) I've got a fan dipole that I've put up, along with a NanoVNA-F V2 and I'm trying to learn the use of the NanoVNA and which characteristics are worth chasing and which I can control (vs which I can not)

@ve6wo 5 ай бұрын

Yes, the change in frequency of resonance when I lowered the antenna was about .02 MHz. From a practical point of view, this is of very little significance. Some other factors that most certainly would have been changed when I lowered the antenna are the antenna radiation pattern and antenna efficiency. Unfortunately, these characteristics are not easy to measure. So, I guess what I’m trying to say is that just because an antenna is resonant, this does not mean it is efficient or well suited for the mode of propagation you are wanting to employ. As an example.. using a vertical antenna with a low angle of radiation when you wish to communicate via near vertical incident skywave is counter productive.. you want all your RF energy to go straight up, not down low towards the horizon. So, to help along your likely never ending path of discovery when it comes to antennas, don’t focus on only one thing, like input impedance, or SWR, or making your antenna resonant.. there is a much bigger picture there and if you’re anything like me, the more I learn about things the more I realize that I really have much more to learn! Haha!

@donepearce 7 ай бұрын

Please abandon VSWR and use return loss (in dB). You get so much more information, particularly when you have a good match. And do remember that you are measuringa combination of radiation resistance and loss resistance. You don't want to end up matching into a loss resistance.

@Swede_4_DJT 6 ай бұрын

Where did you get your "shell" or that green frame for the vna in your video thumbnail?

@ve6wo 6 ай бұрын

KC3UDZ makes them! www.qrz.com/db/KC3UDZ

@Swede_4_DJT 6 ай бұрын

@ve6wo Greetings from Sweden! I appreciate your quick response and also the link. Will check it out now.

@vladtepes481 7 ай бұрын

You need to know the impedance at the antenna. To do this, the reference plane must be at the antenna feed and not in the shack.

@aWeRCHeli 7 ай бұрын

But he shifted the reference plane to the part of coax, where antenna is connected -e.g. beginning . This should allow the same measurement as it would be directly connected to the antenna.