Excellent talk on impedance matching, co-ax length and the impact of getting it wrong. Shows the value of a good analyser (and knowing how to drive it of course).
My understanding is that the coax length just fools the meter at times. I don't know about the Rigexpert, but most SWR meters just measure the voltage min and voltage max and uses that to calculate reflected power. The problem is that standing wave voltages will interact with the signal voltages, cancelling them at some points and amplifying them at others. So wherever the meter is taking it's measurement is going to determine what Vmin and Vmax values it sees. But just because your meter is at a point where the standing wave and forward waves cancel, doesn't mean you have less power being reflected. It's just that the meter sees a low Vmin to Vmax ratio and assumes the reflected power is low.
Great video. Thanks Kevin for the presentation and Jason for recording it. I'm going to spend some time on electrically measuring my coax and optimizing my antenna systems.
I suggest everyone who concurs with the info relayed in this video, buy a copy of and read the ARRL Antenna handbook/ Radio Amateur Handbook. This is Misinformation on transmission line theory. Put a 50 ohm dummy load at the end of any length 50 ohm coax and it will flat line your analyzer in the HF ham bands, no half wave necessary !!! 57588 viewers mislead.
The length of the coax matters more to obtaining a perfect match to a 50 Ohm load of a monoband station. Type of cable and quality of cable has more to do with db loss at particular frequencies. Higher the frequency more loss. Moving from band to band on a multi-band antenna would require an antenna tuner as the ham bands frequencies are not multiples of one another. So although, half wave increments gets you close it a match, it will never get you spot on unless you are using a dedicated monoband station. I have tried to explain this to several people yet no one seems to grasp the concept. Keep in mind that per meter, coax has a inductive and capacitance value to it. So with that being said, LC networks are frequency dependant when trying to achieve a 50 Ohm match.
I have made a couple of the 49-1 transformers and as expected had a good match on a end fed wire when the wire was a half wave on 40, then it is a full wave on 20 and etc. across the bands that Are a multiple of the preceding band. The impedance of a end fed being 2500 to 3000 seems to not care if the wire is a half or full wave. I did not get a good match at 10 mtrs. but it was fine just below 28. Now the WARC bands are not covered. So I make a full wave at 17 mtrs and got a perfect match to the coax but just did not hear any signals to work, so down it came and back to half wave on 40, It preformed great, does not seem to radiate that well on 20 but is a perfect match to the coax. The wire is a inverted L from 5 feet at the feed point up to 45 feet on the stand off on the tower and then down to a tree limb. Dave, W4GSM.
@@1903A3shooter A 49:1 transformer work wonderfully. Now try to make a 70cm 1/4 ground plane antenna, get it to resonate on frequency then change the coax. You will see that your SWR will change. Which will mean that cuz the random length of coax has affected the impedance of the antenna.
I understand the half or full wave multiples. When precisely executed, you will see the complex impedance of the antenna at the shack end. Although, if the load and source are both 50 ohms, and the coaxial cable is 50 ohms, there will be no transformation of impedance. I know, this is an unlikely, perfect scenario/example, but I thought I should point this out, and in this instance, any length of coax can be used. I'm not a ham.
Nope incorrect, you have an expensive hunk of Junk. NanoVna sooooo much less money and worth more as it does 10 times the amount of things a Rig Expert could ever do.
Very informative video. When I finally build my shack, I'm going to watch this video again and take notes on how to get good results from a wire antenna to start off with.
Good luck . I didn't learn anything because he is jumping around to much. A lot of those ya -hoos have a lot of secrets and they are not gonna give them up
Ham Radio Tv, You're video has given me the opportunity to experiment/test/use the right coaxial cable length for my 11 meter antenna. I always knew if the right type of cable/balun were used I would have a perfect antenna. This video just proved it. I now have subscribed to you're channel.
Great video. I am glad you gave an honest opinion of HWEF antennas. I use one for portable operating, along with my KX2, all of the time. Super easy to erect and they are passable RESONANT antennas. Mine is 65 feet 5 inches. I also use a Rig Expert analyzer. The one I use most is the 230 Zoom, but I do have an AA-600 as well. I leave my 230 set for 250 sampling points. But I like that they finally got away from limiting you to only 80 sampling points like the AA 600 has. Barry, KU3X/QRP
Excellent video. I have a 9:1 unun and a 1:1 current unun from the "three letter" company. I measured them with my AA-600. The 9:1 seems great. The 1:1, not so great. I opened it up and it appears the "three letter" guys used the wrong mix of toroid as the core. I'm checking that out with them. My homemade 1:1 with snapon toroids made out of type 43 material works MUCH better from 1.8 to 29 mhz. I totally concur with your assessment of the performance of some of the commercial ununs Kevin. Keep up the good work. I would like to see a video on 1/4 and 1/2 wavelength measurements with the Rigexpert analyzer. 73, and thanks. Bob, K5INW
Great video. I'd like to know what size are those ferrites 31 and 43. Where can i purchase those. Do you have instructions on how to build the 2 matching devices thanks. VE2OPR
One little detail bothers me about this experiment. ..... Putting a choke at the input of the 49:1 transformer will block any displacement current and the antenna will basically not work unless you have a ground or counterpoise on the secondary. I've tried this! You can put a choke at the shack end of the coax with no problem but the system needs some metal to supply that small amount of return current. Join our EFHW group for more detail facebook.com/groups/EndFedHalfWaveAntennas/
So what antenna analyzer is suggested? From what I can tell the RigExpert seems to be the best according to reviews and number of features. There are some out there that are rated well, but most of them don't have cable testing capability. I have my eye on the AA-600, but man I'm going to have to save for it and it will definitely get a Pelican style case. I've considered the MFJ-269C, but I often read QA and Build complaints about MFJ, and people mentioning how out of calibration they can be. If you suggest anything else let me know.
Both are good. I've used multiple MFJ's with no problems. The newer RigExperts seem to be more innovating with their designs and screens. But, having an analyzer is extremely helpful. Even if you are just borrowing it.
If your antenna, or dummy load, or whatever, has say, an SWR of 1.5, at no point along the coax will that reading increase, that is unless you have another problem. The waveform you are showing on your rigexpert looks more to me like a common mode current waveform, and when I see it on either of my VNA's I always add a choke or a balun and the problem always seems to go away.
Let's say it's just common mode current.... Y add a choke or ballen when you could just add nothing and make the cable the length that doesn't cause an issue
Hi Kevin. Great video. Could you possibly do a quick video tutorial on how to get the Antscope software installed and how to hook the AA-600 to a PC? I have installed the software but I cannot figure out how to get the computer and analyzer to communicate.
what can we do about the length of cable when trees dont always grow at the right distances away from my shack to hang antennas? It shows having the right length and type of cable makes a big difference in the video.
Hello. I'm Japanese. I have two question. Is the version of the computer that this analyzer is connected to Winodws10? Also, does this software work properly on a Winodws10 PC?
Hi, would you please to share the reference to 1:1 current balun from your efhw setup? It is clear about 1:49 transformer but please share the details about current balun (material, number of turns, etc). Thank you
Where is this club located? The only other club I've seen like this was back in Memphis when I first became a ham, they begged me to join and I said no, sigh, young and dumb.
Hello from Atlanta Georgia I thought your presentation was excellent I'd like you to do more videos and explaining all these wonderful things for amateur radio yes that rig expert seems to be a very popular unit right now over the mfj analyzer let's put it this way at least you don't have to put 10 double a batteries in it hahaha thanks for sharing
Joe Framo Thank You and we sure will keep making videos!! Yes, so many darn batteries in the MFJ’s! I’m sure it keeps the cost down instead of putting a rechargeable battery in them.
@@HamRadioTV you're my friend thank you for responding to my text you know not a whole lot of people do they don't pay attention but you actually answered my text thank you yeah I was looking at the mfj analyzer but when I found out it takes 10 double a batteries besides you have to take like eight screws out to get to the inside I don't understand why they didn't put some kind of Alachua on there you can take it off easy yikes anyway thank you for sharing it's such a great analyzer and I believe it only takes two Double A's that works for me take care of my friend keep up the good work
I'm always happy to chat with all the people I get to meet online that also shares this great hobby. After all, the interactions is why I do it! Thank you for being a part of it!
In this video Kevin / N6VLF is using a RigExpert AA-600. He then tries different homemade baluns with different types of coaxs. Instead of having an actual antenna hooked up for this demo he put a 50 ohm resistor in it's place.
The simplest method for determining the right length of any feed line is it has to reach the antenna from the radio. More usually doesn't hurt. Not enough is a real 'pita'! An easy way to do all the impedance juggling is to use a tuner. No, they aren't that lossy and make things easier which is the whole idea. The use of the software is nice, but not necessary at all. Oh well, I'm not selling anything either.
KN6BST Unfortunately we don’t have the exact designs on hand. Kevin had researched it on the internet and went off of that. We are planning a future balun / unun build video, so stay tuned!
So, if someone is still monitoring this vid, how does the layman know roughly what length coax to use? Should we stick with 1/2 wave length increments?
Start with 1/2 wavelength. Due to velocity factor the tuned length will be shorter. So then you connect an antenna analyzer to determine how much to remove in order to tune to resonance.
@@SMShannon55 : Fact is, if the antenna is tuned properly and has the proper counterpoise, the coax should be invisible to the system. Therefore, coax length doesn't matter.
@@TheLonesometoad - except that there’s no perfect coax and never a perfect counterpoise. If you want to get the most out of an antenna system the length of the coax is still important.
We need an affordable tool to measure common mode attenuation of chokes... there are sooooo many out there that CANNOT be tested because we do not have the right measuring tools... you think your choke is doing the work but it's probably not... specially if you do "ugly balun" air core chokes... I just wish those rig expert meters could test attenuation and impedance of chokes...
@@joerowland7350 those aren't super precise, they vary readings from one another, you need the right adapters and OSL kit to adapat to the right connectors...
@@Aleziss I have Rig n mfj aa hp vna the nano is really close n I bout a nice set of adapters from rfpart long ago I know the nano not cert calibrated n I just got it not long ago but it's handy for a lot of things n a real good for the money I payed like 119 for it Mine is the f
@@joerowland7350 ok mine is the nanovna-h (nanovna.com), I even see differences between the nanovna and the nanovna saver software which usually give higher results... difficult to understand which is giving the right readings. Mine use SMA connectors, then I need SMA to BNC then BNC to banana plug (to connect balun leads).
That is a great piece of kit! I spend more time learning and working on Ham Radio then I do talking on the radio, lol. That's what makes this hobby so interesting. Have you been able to find many videos on your AA230?
SKW I’m not sure what you mean. I shoot and edit all of these my self during our monthly club meetings. I’m very flattered your enjoying them and stay tuned for more as we recorded them. 73 Jason KM6FAK
@@HamRadioTV I thought maybe you might have a website or something besides RU-vid that has a collection of these. Anyway thank you for letting me know. This speaker clears up alot of things for me to better understand the subject, and I'll be sure to look for upcoming videos. Keep these great videos coming. 73s Sterling WH6WJ.
@Ham Radio TV I thank you for posting these as well and wish more clubs would record and post their presentations. It gives others ideas for their clubs and it educates those who dont have a club nearby or are unable to get out to the meetings.
Using old lighting bolt that out of business now. Work great, moist weather mess with it. Just want to use it again. Thinking about 75 loop about 60 feet
Don't know what to use, I think I can make one, not use of the parts and wire. I hear Teflon wire is fantastic to work with but I don't know where to get it I live in Florida so a ARS is a thing of the past
I just received a rig expert 500 yesterday and have an ungodly number of problems with it and no way to really contact anyone for help except an email in ukraine. When you finally locate the manual it's in a font size smaller than anything I've ever seen in my life when you print it out, the software doesn't work on any of the three computers that I have and it screwed up the booting on two of them. When you change velocity factor in the settings it's not reflected when you go to take the measurement. The manual does not include any instructions on the functions on the second screen. To top it all off there's really no f****** help at all from the rig expert company for any of these problems they sell it to you and then tell you to go to hell.
Well, one must take in the velocity factor, and the so called CB myth usually refers to free space. So let's just say the shield is a half wavelength for, maybe, counterpoise purposes, or a short to RF. However, common coaxial with a VF of 66%, that length comes out very close to 3/4 of a wavelength. I find that interesting. Is there more to it than what people usually judge? And which one is it (apart from the advantages of half wave or multiples thereof)?
This us all a neat trick, but you've jumped into a rabbit hole, and you're misleading basically all the new guys that have been asking me this, im quite upset that a ham is going on about this. You're using loss to make up for the unun's inherently poor performance, especially a 9:1. Stop treating your feed line like its part of your antenna. The best coax is the best you can afford, and the shortest you can make it.
So you get more than half way through the tutorial and have to stop to explain why the resistors are there. And this takes some time. I'm a CBer and I'm already ten steps ahead. What does that say about the intellect of the average ham?
Thanks for watching. These presentations take place at our club meetings and we always include everyone. There is no stupid questions, and we would never belittle someone for not understanding or having advance radio knowledge. I leave some of these questions in the video, as others on RU-vid might have the same ones. You can have all the knowledge in the world and all the radio equipment, but if there is no one to talk to on the other end, what's the point.
@@HamRadioTV you mean quiet. I remind you, I am a CBer. I will never be a HAM, nor do I want to be. And I do not need to be for knowledge on antennas. And you mention asking questions, well that was just my point, so it still stands. I have a lot of friends on the radio, and my knowledge and help is appreciated. I don't however feel the need to put on lame seminars. And what's with the late reply?
@@HamRadioTV Sorry. You should re-read my comment. My comment indicates that there are no stupid questions. Please don't lump me in with Jeremy Frances.
