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16 Director Mod
2 Attachment(s)
After disappointing results adding four elements on to the existing factory antenna (Mod 1), I figured it was time to go for broke. I was already geared up to go further anyhow.
Mod 2. I sacrificed one of the reflectors from one the donor antennas and cut 4 new directors to continue the pattern. So, the last 6 directors are all 21" and spaced 10.5" Without any specific antenna modeling it seemed like like a logical step. I sleeved the inside of the boom with "U" (technically C-Channel) and laid it on the 3/4" under support which I had left extended on the first mod, I figure it would come in hand and it did. I also fabricated a tab so I could attach the upper support cable to the end. The cable is pulled fairly tight. It is fairly solid and withstood 45 mile an hour winds already. http://forum.tvfool.com/attachment.p...1&d=1587557730 I wanted to put the boom attachment clamp closer to the center of the antenna but my reinforcements don't allow for that. I'll have to research adjustable beam clamps or, of course fabricate my own. Testing: So-so results. After several comparative tests, I believe these will be the most consistent results. Maximum delta measured was + 2.84 dB. Overall, it's more like 1.2 dB and at the very end the two patterns seem to blend. RF12 is not in the antenna aim market, it is being picked up from the back of the antenna. http://forum.tvfool.com/attachment.p...1&d=1587555244 |
You might want to use a Yagi calculator such as the one below to give you some ideas. Normally each director (also known as parasitic) element of a Yagi antenna will decrease in length the further it is from the driven element. They will also get further apart as the distance from the driven element increases. If you are looking for an antenna specifically for RF 8, try modeling a 17 element yagi at 183 MHz using the calculator and compare the results to what you have.
https://www.changpuak.ch/electronics...enna_DL6WU.php |
Good info.
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Thanks for the information. Not specifically RF 8 that I'm after, it's just a transmitter I am using to measure my results. One reason is it is at least 49 miles away and makes it a far enough target. I could turn the antenna around and check RF12 also, but for now I like RF 8 because soon trees will leaf out in the path of RF12 and would destroy my baselines. I will test RF 12 soon enough though. before the leaves! I don't know how to use the modeling software, I hear it is extremely tedious. I'm willing to learn it but I may have to do it later. I am hoping to find that someone has already tried this. I sent Holl_ands a PM but no reply. He has done the modeling but no mods so far that I know of. What you did say was the director should begin to taper down and the spacing should widen. That is also of interest to me. I did go to the link you sent, The picture show something similar to mine actually with some broken elements. The calculator is there, and although I can change the # of elements, parasitic elements and diameter of the boom, I click on "Show me the details" The boom should be 7.29 meters ! 14.20dB of gain. Nice. Can I choose the length of boom I want? And then build it from there? Some other questions. What is an isolated Element? Reflector? What to do with that? Would I change my Dipole dimensions? BTW, 26' 7" for a 17 element at 183 MHz whoa! |
183 MHz
Frequency : 183 MHz
Wavelength : 1639 mm Rod Diameter : 10 mm Boom Diameter : 18 mm Boom Length : 7290 mm d/lambda : 0.006 ( min.: 0.002 , max.: 0.01 ) D/lambda : 0.011 ( min.: 0.01 , max.: 0.05 ) Elements : 16 Gain : 14.20 dBd (approx.) ------------------------------------------------------------- Reflector Length : 790 mm Reflector Position : 0 mm ------------------------------------------------------------- Dipole Position : 393 mm ------------------------------------------------------------- Director #1 Position : 516 mm , Length : 745 mm Distance Dipole - Dir. #1 : 123 mm ------------------------------------------------------------- Director #2 Position : 811 mm , Length : 738 mm Distance Dir. #1 - Dir. #2 : 295 mm ------------------------------------------------------------- Director #3 Position : 1164 mm , Length : 732 mm Distance Dir. #2 - Dir. #3 : 352 mm ------------------------------------------------------------- Director #4 Position : 1574 mm , Length : 726 mm Distance Dir. #3 - Dir. #4 : 410 mm ------------------------------------------------------------- Director #5 Position : 2033 mm , Length : 720 mm Distance Dir. #4 - Dir. #5 : 459 mm ------------------------------------------------------------- Director #6 Position : 2525 mm , Length : 715 mm Distance Dir. #5 - Dir. #6 : 492 mm ------------------------------------------------------------- Director #7 Position : 3041 mm , Length : 711 mm Distance Dir. #6 - Dir. #7 : 516 mm ------------------------------------------------------------- Director #8 Position : 3582 mm , Length : 707 mm Distance Dir. #7 - Dir. #8 : 541 mm ------------------------------------------------------------- Director #9 Position : 4148 mm , Length : 704 mm Distance Dir. #8 - Dir. #9 : 566 mm ------------------------------------------------------------- Director #10 Position : 4738 mm , Length : 700 mm Distance Dir. #9 - Dir. #10 : 590 mm ------------------------------------------------------------- Director #11 Position : 5352 mm , Length : 698 mm Distance Dir. #10 - Dir. #11 : 615 mm ------------------------------------------------------------- Director #12 Position : 5984 mm , Length : 695 mm Distance Dir. #11 - Dir. #12 : 631 mm ------------------------------------------------------------- Director #13 Position : 6623 mm , Length : 693 mm Distance Dir. #12 - Dir. #13 : 639 mm ------------------------------------------------------------- Director #14 Position : 7270 mm , Length : 691 mm Distance Dir. #13 - Dir. #14 : 648 mm ------------------------------------------------------------- Directors / Parasitics are isolated. Please choose an isolater thicker than : 9 mm |
220 Mhz
Frequency : 220 MHz
Wavelength : 1364 mm Rod Diameter : 10 mm Boom Diameter : 18 mm Boom Length : 6068 mm d/lambda : 0.007 ( min.: 0.002 , max.: 0.01 ) D/lambda : 0.013 ( min.: 0.01 , max.: 0.05 ) Elements : 16 Gain : 14.20 dBd (approx.) ------------------------------------------------------------- Reflector Length : 663 mm Reflector Position : 0 mm ------------------------------------------------------------- Dipole Position : 327 mm ------------------------------------------------------------- Director #1 Position : 430 mm , Length : 625 mm Distance Dipole - Dir. #1 : 102 mm ------------------------------------------------------------- Director #2 Position : 675 mm , Length : 619 mm Distance Dir. #1 - Dir. #2 : 245 mm ------------------------------------------------------------- Director #3 Position : 968 mm , Length : 614 mm Distance Dir. #2 - Dir. #3 : 293 mm ------------------------------------------------------------- Director #4 Position : 1309 mm , Length : 609 mm Distance Dir. #3 - Dir. #4 : 341 mm ------------------------------------------------------------- Director #5 Position : 1691 mm , Length : 605 mm Distance Dir. #4 - Dir. #5 : 382 mm ------------------------------------------------------------- Director #6 Position : 2100 mm , Length : 600 mm Distance Dir. #5 - Dir. #6 : 409 mm ------------------------------------------------------------- Director #7 Position : 2530 mm , Length : 597 mm Distance Dir. #6 - Dir. #7 : 430 mm ------------------------------------------------------------- Director #8 Position : 2980 mm , Length : 593 mm Distance Dir. #7 - Dir. #8 : 450 mm ------------------------------------------------------------- Director #9 Position : 3450 mm , Length : 591 mm Distance Dir. #8 - Dir. #9 : 470 mm ------------------------------------------------------------- Director #10 Position : 3941 mm , Length : 588 mm Distance Dir. #9 - Dir. #10 : 491 mm ------------------------------------------------------------- Director #11 Position : 4452 mm , Length : 586 mm Distance Dir. #10 - Dir. #11 : 511 mm ------------------------------------------------------------- Director #12 Position : 4977 mm , Length : 584 mm Distance Dir. #11 - Dir. #12 : 525 mm ------------------------------------------------------------- Director #13 Position : 5509 mm , Length : 582 mm Distance Dir. #12 - Dir. #13 : 532 mm ------------------------------------------------------------- Director #14 Position : 6048 mm , Length : 580 mm Distance Dir. #13 - Dir. #14 : 539 mm ------------------------------------------------------------- Directors / Parasitics are not isolated. The length has been increased to compensate for that. |
The answer to your questions is below in blue. I have only built one Yagi for TV and that was years ago and it worked very well pulling in a weak station (before the days of digital TV). I have used several for VHF and UHF ham radio bands.
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Thanks Tim, I'll look at that dipole calculator.
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Again thanks for the info you just made it interesting for me! |
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You might want to check out a log periodic antenna. Enter your min and max frequency and maximum boomlength into this calculator (https://www.changpuak.ch/electronics/lpda.php) and see what you come up with. You could probably get about 10 or 11 dB of gain on a 12 ft boom with about 15 elements. |
Thank you again Tim.
So, because I would have to start completely over to build a log periodic it looks like I probably won't do that right now. I guess I would be a project for another day. So speaking of the out of the box HI VHF yagi antennas. Are they generally designed for the middle of the spectrum? I mean how does the company come up with an antenna like the 30-2476 that performs well across the VHF High Spectrum? |
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I would speculate that building an antenna to cover a band 42 MHz wide is much more complicated. Have you ever taken a look at this web page that has a lot of info about a number of different antenna types? https://imageevent.com/holl_ands;jse...s441x1hne1.dog |
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http://forum.tvfool.com/attachment.p...1&d=1588993197 http://forum.tvfool.com/attachment.p...1&d=1588993384 http://forum.tvfool.com/attachment.p...1&d=1588994052 |
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I did pick up a 20-foot piece of one inch by 1 inch aluminum square tubing with a .125 wall. But the 20 foot piece actually sags under its own weight. Since this antennas and odd design , I will probably come up with an odd brace. http://forum.tvfool.com/attachment.p...1&d=1589300133 Not long ago I saw an antenna on a roof and the boom brace was above the antenna boom. Is there any anything wrong with doing it that way? That opens up couple possibilities if I can do that. |
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VHF super-long yagi
1 Attachment(s)
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http://forum.tvfool.com/attachment.p...1&d=1589549623 I want to say thanks to you guys so far for keeping the interest this project. I haven't put it in the air yet, probably this weekend. http://forum.tvfool.com/attachment.p...1&d=1589556364 |
It has been a very interesting project. Thanks for keeping us updated and sharing the photos.
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Project braced.
1 Attachment(s)
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http://forum.tvfool.com/attachment.p...1&d=1589656098 Hey, you guys ! I over calculated the boom length. There is an extra 20" or so... I wonder if it would hurt to add another director?? I won't do it now. Food for thought though. |
30-2476 MOD 4 Modeled Yagi
1 Attachment(s)
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30-2476 MOD 5 Modeled Yagi VHF
3 Attachment(s)
All I did was put the reflector from another 30-2476 on this new Super Long Yagi. I had to remove the single reflector and put the 4 reflector on:
http://forum.tvfool.com/attachment.p...1&d=1590556852 http://forum.tvfool.com/attachment.p...7&d=1590557140 Not much of a change, also, in the notation under RF8 Milwaukee, it says "Chicago", disregard that it should say that under RF12, oops: https://i.ibb.co/rfg3f9z/VHF-MOD-4-V...g-Yagi-VHF.jpg Getting some usable UHF ! : https://i.ibb.co/PxG3HBf/UHF-scan-on...g-Yagi-VHF.jpg |
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