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- เผยแพร่เมื่อ 16 ส.ค. 2024
- This single band half-wave vertical works extremely well for DX, and is easy to deploy. The antenna was in the December 2021 issue of QST magazine and this video will show more detail and focus on how to get the matching section tuned and built. No 49:1 transformers to wind and no radials needed on this antenna. #ARRL #W8TJM. #Antenna
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This is such an excellent video, Toivo. Bravo. I've been poring over your video on the 10m Moxon in recent days, and gathering parts I will need to replicate it. My wife keeps asking why I would ever need four fishing poles when I don't even fish. Now I fear she might be wondering why I am burying a PVC pipe in the yard and very delicately snipping bits of wire of the end of a ladder line in the driveway. I'm so grateful to have HAM operators such as yourself providing such valuable information on TH-cam. In my small community, I don't have any elmers to lean on, so information provided by those such as yourself is invaluable. Cheers and 73. Jason W2ASH
For making moxon antenna I bought a lot fishing poles and after that I am fishing man now😂
This is really good, thanks, and I've linked to this video from my own antennas website.
Nice work. very effective and simple antennas, especially for single-band dxing. I have a 15M version and it is simply fun to use -- your installation method on fiberglass poles is simple and effective especially for portable ops. It can handle legal limit too !
Best vertical video everrrr! Seriously. Nice to keep it simple. Thank you and 73. K1QS
Just discovered your channel, but this video ticks all the "yes!" boxes for me, especially the benefits of the half-wave vertical and the use of the excellent RigExpert analyser. Nice clear explanations too, no fluff! Oh, and adopting the metric system makes wavelength conversion easier... 😉👍
Great video. I really enjoyed it. Easy to follow instructions and some neat tips along the way.
Barry, KU3X
Thanks Barry! Coming from someone as experienced as you, that is a big compliment. 73, Toivo
Thanks for the video, Toivo! The extra detail is very helpful. Your explanation of how the matching stub works was great. Other explanations rapidly got into way too much math for me. My 20 meter version is finished, and as soon as I move some coax from another antenna, I'll have the vertical on the air.
I've been a ham for 40 years and never had anyone explained how to match a 1/2 wave antenna with the matching section 0 impedance at the shorted feed and super high impedance at the other - just find a point on the matching shunt that is about 50 ohms along the linear length.. Bang! an Ah Ha! moment.
Thanks for that comment! Makes posting these worth the time. Transmission lines are pretty amazing. If there is any other topic that interests you, fire away.
@@W8TJM you're very welcome. When I found your video it was great I mean you have good quality and you explain things well I was surprised you only had 18 or so viewers I guess ham radio is kind of a small audience. Keep up the good work I'll check in.
nice video thank you
I will be hanging a 12 m ver. today KJ9P
Gee one lonely American, using metric. hi hi. Thank you for you video, top stuff. vk4.
If you are building a 10 METER VERSION, Email me (QRZ.com for my email) for a corrected table of measurements. Not sure how the error crept in by I redid the 10 meter version and have better dimensions. It has been working great!
Thanks for the informative video. Could you give me some specifications on the toroid that you used for the choke please. I will need to order one in. Thanks, Frank VK4FEM
I normally use 12-14 turns of RG-58 on an FT240-31 toroid for 20 meters, and 10 turns of RG-58 on an FT240-61 for ten meters. 73!
Frank.... Also, Google "G3TXQ chokes" and you will find some charts on how to select the best torroid for a given frequency and coax.
how does this compare in losses to a decent autotransformer or "unun" like 49:1 commonly used for end fed antenna?
Quarter wave transmission lines are extremely efficient so the loss is extremely low. No ferrite or winding coupling losses to consider at all. Big disadvantage is that it is single band, but it does give you the most efficient half-wave antenna possible. Those 49:1 all band solutions are a compromise, but they do work once you tune them in.
@@W8TJM i will try one for 10 meter band honestly, lower frequencies seems like too much hassle adding the extra 1/4 wave twin lead makes things much longer and unwieldy.
do you have the correct 10 meter measurements?
@@Gabaab Send me an email on my QRZ.com page and I will send you the most up to date dimensions.
Everyone else uses 49:1 matcher using toroid core 240-43
49:1 transformers are certainly a viable option to get on the air and I have used them in the past. The 1/4 wave matching section in the described video technique allows significantly higher currents and voltages in the resonant radiator so the antenna effectiveness is much higher. Keeping the radiator vertical allows very low take-off angles which is important for DX.
@@W8TJM ok thanks. im in the middle of building my efhw vertical made of aluminum tubing for 10 meter. Mounted on side of house 30 feet up on either pvc or steel pipe mast. Running legal limit. So im much better off with your way? Few years ago i built a 11m half wave using gamna matching ring (I think its called) few feet of 1/4" copper tube for ring attached from radiator tube to ground at the feed point with the coax center tapped to the ring which did well. Which option you think ill be best with. Im near nyc My elevation is 300' would love to dx across the Atlantic as well as local. Thank you. 73s
@@gabrielM1111 You won't have any trouble working across the Atlantic in the next few years on 10, 15, or 20 meters with the solar cycle improving so rapidly now.! Look me up on QRZ.com and send me an email and I can send you some information. 73
@@W8TJM Sorry better recheck you data on that
Nice video. What would be the effect if this were made for 10m and both the radiator and stub were held vertical on a 30' mast? I presume behavior would be similar to a typical 2m j-pole but I wonder how it might affect the takeoff angle vs the stub in a horizontal configuration. KB9LNS
Thank you for the question! I do exactly that on my 15 and 10 meter antennas. The takeoff angle in not affected as the matching section does not radiate. As long as the matching stub is loose against the mast, the same dimensions work. Tightly wrapped, the velocity factor is reduced due to the mast so it would have to be slightly shorter. Lately, I have been using my 15 meter vertical a lot as the band has been fairly open.
I stumbled into your video over a cup of Joe this am. So glad I did. I am smack in the middle of half-wave vertical experiments. Right now, end fed half wave graound mounted vertical feed methods are on the agenda. Looking to evaluate QRO opetions for convenience and efficiency. Coupled air core vs toroid core, vs tapped, vs difference capacitance options. What a blast I am having! Once I have my answers, I'll move to phased verticals using the results of previous discoveries. Anyway, I have a couple of questions: do you have any idea how much power this matching method will handle? I presume, full legal limit HF. I am curious if you've tried matching .05 wavelength instead of a quarter wave? That .05 Lambda length keeps popping up on me, and I'm just wondering. Also, do you notice considerable variation when antenna is closer to ground, say 1 Meter? I suppose you want to perform tuning at the actual location and height since tap point may change. I really enjoyed your presentation of this project. Thank you for sharing! 73, Kenny, NZ5i
Kenny, Thanks for the comment and glad to hear from another antenna experimenter! I run a kilowatt with the antenna but have to be careful on wet days. The end of the matching section is very high impedance so the voltage there is in the thousands of volts. I have had arcing with sustained corona at that end, so I normally try to insulate the un-terminated end of the matching line and bend it away from the terminated end. I have not tried .05 lamda matching as I don't think that will transform to the extremely high impedance at the end of a half wave radiator. Also.... The antenna SWR is not very sensitive to height above ground, although the take-off angle does change.
@@W8TJM Very good to know. I guess weatherization needs to be a consideration to take seriously if operating in the wet weather. I am very curious how this feed method stacks up in the efficiency / bandwidth dept? This is turning out to be a bit of a shootout of sorts. No single method of coupling high impedance to low seems to be perfect. Each has pros and cons, I'm discovering. Anyway, thanks again! Great video
@@kennymanchester Main disadvantage is that it will be a mono band solution. Efficiency is maximized with the transmission line method as there are no ferrite losses, and no mis-match losses. It is tuned resonant matching schema for a single band. Have fun with the shoot out and let me know what you find out. 73, and thanks again for the comments.
@@W8TJM Yes, a mononband solution is ok. It will be interesting to see how this match plays next to a air core, coupled LC. One more question comes to mind; what happens if we "roll up" the matching section and and place it in a box? A couple of the L-C combos I am messing with use coax for capacitance. Once it's cut, it can be folded up and put away. Of course this is not the same thing, but still wondering if the stub section can be bent with some tap/length adjustments to compensate?
@@kennymanchester The matching section needs to behave like a transmission line, and it can have gentle curves or sags in it. Coiling it would cause it to couple to itself and its behavior would change drastically. It can tolerate some bends so experiment with it to see what works/happens.
i have already tried several j-pole antennas. unfortunately, i found out that the adjustment to the ladderline results in a significant loss of power. the only question is how much ;-) 73s de DL9HD
Transmission line matching has very low loss so wondering where your losses may be occurring?? Currents are low everywhere except the shorted end which has minimal length so resistive losses are negligible. Mismatch loss should be very low if you do get the right tap point, matching section length, and resonant half-wave length. (Those are important.) I have found these antennas to be very efficient.
Thanks for the sharing mate. If use 300ohm is there any calculation formula? I have some 300ohm with me. I may use what i have
The length is determined mostly by the velocity factor of the transmission line section, and your 300 ohm might need to be slightly shorter than when using 450 ohm. I hope to work you on the bands Mohamad! The 300 ohm should work fine.
Thanks Mohammad, I was thinking the same question. I have been unable to get 450ohm Ladder Line, but was able to get some 300ohm as an off cut from my new club. Frank VK4FEM
Nice video. Hope to see you on band some time. 73 de VU2JO
Thanks Jon! Would love to work you this summer as conditions peak. Take Care and keep having antenna fun!
@@W8TJM Sure!