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6m Beacon Antenna ... |
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| Author | Post | ||
| Mark, PA5MW |
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Mark, PA5MW  Registered Member #259 Joined: Mon Apr 14 2008, 01:52PMPosts: 7 | I know that George at  designs and manufactures all kind of antennas. Both his yagis and verticals are HD, designed to withstand wind and salt water at the dutch coast (see also PI4COM).I'm sure George is capable of producing VHD (Very-Heavy-Duty) versions of a 6m vertical if he is well instructed. For JX7DFA I'm willing to assist by paying the shipping costs. 73 Mark, PA5MW http://pa5mw.blogspot.com | ||
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| Mark, PA5MW |
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| Mark, PA5MW Registered Member #259 Joined: Mon Apr 14 2008, 01:52PMPosts: 7 | Another tip I learned this week from the someone who services our dutch navy : Tilt your vertical by max 7deg. This does not affect the antenna pattern but dampens its self resonance. On ships it is the self-resonance which causes vertical antennas to break, no matter what length/size, so I'm told. | ||
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| Per, LA7DFA |
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Per, LA7DFA  Registered Member #189 Joined: Sun Apr 06 2008, 04:05PMPosts: 44 | Hi Mark, thanks for the tip. Can you try to find out the price for such an antenna? One important parameter is the lenght. It should be be short to reduce stress. Perhaps a helix wound vertical would be a good solution? Better with less gain to keep it sturdy. | ||
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| Charly, OE3KLU |
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Charly, OE3KLU  Registered Member #927 Joined: Sat May 16 2009, 12:39PMPosts: 10 | Tks Mark for the Info - George is an old Friend but i had YAGIs and QUADs in my mind when i think on him * hehe * Have send a Email - let`s see what happen  73! Charly OE3KLU PS: Beacon is on the air now with a "summer Antenna" 50.066 Mhz | ||
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| Peter, PA2V |
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Peter, PA2V Registered Member #76 Joined: Fri Mar 21 2008, 04:20PMPosts: 21 | Hi Guys. Just red the lines about the need for a all weather type antenna. The same demands occured for the PA3HEN/MM operations. He was in all kind of weather situations. After a study on his demands (horizontal polarisation) and a lot of playing with computer assisted designs (MN & YO)we came to the "corner dipole". Read the story here: It is still available on the uksmg pages. After many years the dipole was returned to me. It was very obviouse that it suffered from the hard sea life! But is was still alive. Beware to put on a kind of coating on the aluminium elements. I did not and saw a lot of deap corrosion on the aluminium. Hope this helped a bit. Good luck & 73, Peter | ||
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| Per, LA7DFA |
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| Per, LA7DFA Registered Member #189 Joined: Sun Apr 06 2008, 04:05PMPosts: 44 | I am discussing a shortened dipole inside a thickwall fibreglass tube with Mark and George right now. Will post more info later. | ||
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| Zaba, OH1ZAA |
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Zaba, OH1ZAA Registered Member #123 Joined: Thu Apr 03 2008, 02:54PMPosts: 25 | This week I will be prototyping the OH2SIX beacon antenna, projected to be a V-over-V horizontal omni pattern with lengthened dipoles (to get the impedance right). The feed is done with rods inside fiberglass tubes that are supporting the radiator elements (thus partly a 3-layer structure). Will post results later --- 73, "Zaba" OH1ZAA/OHoMZA --- | ||
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| Zaba, OH1ZAA |
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| Zaba, OH1ZAA Registered Member #123 Joined: Thu Apr 03 2008, 02:54PMPosts: 25 | OH2SIX V-stack simulations show that a nice omnidirectional pattern is obtained with 220 cm legs, while the tips are 170 cm apart. The series "lumped constants" (actually tubular capacitors) are 14 pF starting to overlap about 25 cm off the mount point (tower side). With 0.6 wave vertical stacking distance (V-over-V) the gain is 4.05 dBi with 50 ohms feedpoints each. A single V is 75 ohms but only 0.72 dBi with its maximum toward the zenith, so it is not recommended for a beacon. The V-stack with about 20 watts will give nice MS-bursts in the 800 - 1400 km range.... If the bands are not too busy, actual construction and measurements will continue tonight --- 73, "Zaba" OH1ZAA/OHoMZA --- | ||
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| Zaba, OH1ZAA |
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| Zaba, OH1ZAA Registered Member #123 Joined: Thu Apr 03 2008, 02:54PMPosts: 25 | OH2SIX V-antenna measurements confirm the simulation trends. Normally the impedance of a dipole element gets higher when the feedpoint is moved toward the tip of the element. However, when two tips of opposite polarity get near together, there will be additional coupling that makes the current grow due to extra coupling between these points. This calls for shortening of the total leg length and lower impedance. That again forces adjustments of the V-angle to keep an omni-pattern. One trick is to cover the first stretch of the glass fiber tubes with an extra aluminum tube that is grounded, so that the sections nearest to the feedpoint turn into shielded transmission lines. Thus the radiation is pushed to places where it serves the purpose better... "Stay tuned" --- 73, "Zaba" OH1ZAA/OHoMZA --- | ||
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| Charly, OE3KLU |
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| Charly, OE3KLU Registered Member #927 Joined: Sat May 16 2009, 12:39PMPosts: 10 | Mhhhh had not in my mind that it will be so difficult to found an good Beacon Antenna for Heavy Duty use ... Any info still welcome 73! Charly OE3KLU | ||
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