#358

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  • Опубликовано: 29 окт 2024

Комментарии • 56

  • @acestudioscouk-Ace-G0ACE
    @acestudioscouk-Ace-G0ACE Год назад +1

    I've finally found some time to use the early VNA which I bought in the Covid lockdown period... and this set of videos is so useful, thank-you! I hadn't thought of using the VNA in conjunction with my antenna matcher but I will now. What a great idea! 👍👍

  • @Alias_Pistol_Pete
    @Alias_Pistol_Pete 4 месяца назад

    I have been using an end fed random wire antenna for years with great results. The unun is grounded to a steel window well and I also use a choke on the coax just before it enters the shack. The choke is key since it prevents RF from entering the shack

  • @MerlinFox
    @MerlinFox 5 лет назад +1

    Thanks for doing this video. I’ve got the same ATU and will be doing the same when my VNA arrives - EFHW is how I usually operate portable so this will make short work of setting the dials for different bands when in the field!

  • @billryland6199
    @billryland6199 3 года назад +2

    The EFHW antenna needs a counterpoise to stop RF on the coax. A common mode choke will also help.

  • @vironpayne3405
    @vironpayne3405 2 года назад

    Steve Ellington has some excellent videos on testing and optimizing EFHW antennas. The short and skinny is: 1) inverted-L, 2) balun fairly close to ground, 3) good earthground at balun, 4) choke the crap out of balun at the feedpoint, and 5) no counterpoise.
    That should provide a little bit better than 3dB improvement over most installions. It will turn a so-so performer into a good performer.
    Also, usually "A tap" is the full inductor. A general rule for best performance is minimum inductor with high capacitance. It provides the highest Q tuning.

  • @Steve-GM0HUU
    @Steve-GM0HUU 2 года назад

    Good idea to use NanoVNA for this. Takes some of the trial and error out of finding correct antenna "tuner" settings for various bands.

  • @Liberty4Ever
    @Liberty4Ever 5 лет назад +1

    Transmatch + NanoVNA + 5 minutes of knob fiddling = Autotuner. 😀
    Kidding aside, it was great to see how all of this works. Much more educational than pushing the TUNE button. Thanks for these NanoVNA videos.

    • @EvgeniX.
      @EvgeniX. 9 месяцев назад

      there's only so much that an autotuner will be able to handle. those manual boxes have way way bigger tuning range

  • @nickrupp2336
    @nickrupp2336 5 лет назад +4

    A 49-1 UNUN is what you need, not a BALUN. And I think that this is the first VNA video I've seen that is checking an antenna other than a 2 meter or 70 cm. Thanks

  • @robertlundstrom8061
    @robertlundstrom8061 3 года назад

    So what exactly is the vna connected to in back of the matching unit, the transmitter connection? I assume the antenna is connected also.

    • @IMSAIGuy
      @IMSAIGuy  3 года назад +3

      the radio is disconnected and the VNA takes it's place. you wan to radio to see 50 ohms so if the VNA sees 50ohms then you put the radio back in.. same as an antenna analyzer. The VNA outputs RF (weak transmit) and measures the reflected signal for amplitude and phase.

  • @K6TJO
    @K6TJO 2 года назад

    I don't recall seeing how you connected the VNA to the antenna.

    • @IMSAIGuy
      @IMSAIGuy  2 года назад

      antenna connected to antenna connector of transmatch
      VNA connected to radio connector of transmatch
      you wan the radio to see 50 ohms.

  • @researchandbuild1751
    @researchandbuild1751 4 года назад +1

    Im a bit confused as to why you adjusted the inductor? The smith chart seemed to be on the capacitance side at first

    • @thorhilda
      @thorhilda 3 года назад

      You cannot just go up or down in a vertical straight line on a smith chart. When you add or remove reactance with capacitors and inductors, you also move left or right. The shortest and ONLY path toward the center of the smith chart is therefore a combination of two curves. For instance, you must go enough left with the capacitor in such fashion that when you finally add inductance, you curve right, back to the center of the chart.
      See ruclips.net/video/Hsx4wqAlqlQ/видео.html It's easy to explain visually than in words.

  • @Aleziss
    @Aleziss 5 лет назад +4

    and by the way, I am sure you already know this but technically, you need the end fed unun + a 1:1 choke for end fed antennas...

    • @davep6977
      @davep6977 4 года назад

      add an ugly choke (20 turns of coax around a 4-6 inch pvc pipe) See my qrz page W9DLP

    • @jamesbradley9233
      @jamesbradley9233 4 года назад

      Isn't an endfeds ratio 49/1 ?

    • @Aleziss
      @Aleziss 4 года назад

      @@jamesbradley9233 there are 9:1 also that are quite popular but that one is not a resonant antenna.

    • @Aleziss
      @Aleziss 4 года назад +1

      @@davep6977 the air core you are talking are not really efficient, see this page www.karinya.net/g3txq/chokes/ and take a look at this wonderful video of trx bench, now that is a real effective choke that cover all amateur bands and it is quite cheap to build too : ruclips.net/video/JhAPJISUjB8/видео.html (sorry to plug another youtuber video on someone else page) but I sincerly think it is a great demonstration on how common mode choke work and how to build a really effective one.

    • @jamesbradley9233
      @jamesbradley9233 4 года назад

      I made a 9-1 for a random length wire, but an efhw is half wave on the lowest frequency hence the 49/1 I'm building now for this.

  • @SuAmigoElilegal
    @SuAmigoElilegal 3 года назад

    Question. I have a dual antenna whip nagoya. It has 3.5vhf and 5.5 of gain uhf. If i tune the uhf frequencie tona desire, will the gain dimish or be affected and the vhf .

    • @IMSAIGuy
      @IMSAIGuy  3 года назад

      Probably. It depends on the design of the antenna.

    • @SuAmigoElilegal
      @SuAmigoElilegal 3 года назад

      @@IMSAIGuy well it it not fiber glass or dipole or commet antenna is just stell whip antenna Nagoya

    • @IMSAIGuy
      @IMSAIGuy  3 года назад

      @@SuAmigoElilegal I would guess it has a loading inductor and possible capacitor at the base.

    • @IMSAIGuy
      @IMSAIGuy  3 года назад

      what is the model number

    • @SuAmigoElilegal
      @SuAmigoElilegal 3 года назад

      @@IMSAIGuy Nagoya NMO-200A 38.5" Antenna

  • @Aleziss
    @Aleziss 5 лет назад

    in order to take these measurements, you did need to calibrate the device at the end of the tiny peace of coax ? if so, you probably did need to have sma to pl259 adapter, this means the calibration is again wrong because of the adapter ? your you need a calibration set for sma m/f, another one for N m/f and another one for pl259/so239 ??

    • @zachreyhelmberger894
      @zachreyhelmberger894 3 года назад

      I'm no expert at this but I do the calibration with everything but the antenna connected to the VNA, if possbile. But I only have the SMA version of the S. O. L. T . so it is just to the end of the tiny coax. Maybe that is good enough??

  • @paul-c7541
    @paul-c7541 5 лет назад

    I wonder if the Nano VNA could be used to tune I F strips in a radio, I have used a sweep generator , also a Wobbulator , and my spectrum analyser, I've just bought a Nanovna impressive little tool

  • @MrScotchpie
    @MrScotchpie 5 лет назад +1

    Nice video thinking of buying on and looking for a review. You need an unun on an end-fed not a balun. A centre-fed antenna is balanced while coax is unbalanced so a balun, balanced to unbalanced. An end-fed is an unbalanced antenna, so unun.

    • @IMSAIGuy
      @IMSAIGuy  5 лет назад +2

      yes I have a 9:1 unun. I now have tamed the RF return. It was due to a bad ground at the transmatch

  • @antoniopette92
    @antoniopette92 3 года назад

    You are very funny :)

  • @arvinbaba
    @arvinbaba 3 года назад

    Where the tuner device connected ?

    • @IMSAIGuy
      @IMSAIGuy  3 года назад

      the tuner is between the antenna and the NanoVNA

  • @PapasDino
    @PapasDino 5 лет назад

    Think my unit arrives tomorrow!

  • @dave_dennis
    @dave_dennis 4 года назад +1

    Thanks for the informative video. Curious about what you are using as a stylus. My fat fingers can’t pick the right thing sometimes.

  • @kelley64
    @kelley64 5 лет назад

    How long have you been a ham? End fed use the coax as the other side if the dipole? Use a longer piece of coax and ground your equipment.

    • @IMSAIGuy
      @IMSAIGuy  5 лет назад

      Been a Ham since the 1970's extra class WAS WAC DXCC. I had an offset dipole on a 4:1 balun that I set band SWR using my HP8921a. Worked great. I though an end fed would fit my yard better. first time using a 9:1 unun. I've got a good ground on the balun. the ground in the garage is not great. although the 4:1 balun system was working fine. I suppose an RF choke would help things. never had to use one before in all my antennas over the years. different data on wound toroids and multi small cores over the coax. I think I will go back to the windom type

    • @IMSAIGuy
      @IMSAIGuy  5 лет назад +1

      I think I found the problem. bad ground connection to the transmatch. I only added it recently. A flea market find. even without an RF choke things are acting normal.

    • @kelley64
      @kelley64 5 лет назад

      @@IMSAIGuy That's great! I really like Endfed. I do a lot of QRP and live in an HOA restricted area so its end feds for me. I find them easy to put up and tune. I have mine as an inverted L in the attic. Hope to hear you in the air. 73, KF7ZVL. What does IMSAI stand for?

    • @IMSAIGuy
      @IMSAIGuy  5 лет назад

      @@kelley64 IMS Associates, Inc.

    • @bulldogbrower6732
      @bulldogbrower6732 5 лет назад

      Well, excuse me !

  • @rickkf9iv888
    @rickkf9iv888 4 года назад

    Good introduction, could be great if you weren't poking at a screen with so much glare that we couldn't see what you are doing

    • @greglawrencemusic
      @greglawrencemusic 3 года назад

      Here is a more basic introduction for newbies that shows the menu options visibly clear:
      ruclips.net/video/QJYeFpiqY8c/видео.html
      This video assumes you already are familiar with the menu.

  • @andygee873
    @andygee873 4 года назад

    Lefter?? 😂

  • @anthonycardenas9177
    @anthonycardenas9177 4 года назад

    WAAAAAaaa too confusing!

    • @greglawrencemusic
      @greglawrencemusic 3 года назад

      Start here for intuitive clarity:
      ruclips.net/video/QJYeFpiqY8c/видео.html