Low Q Long Yagis by G4CQM for Terrestrial VHF/UHF DXing08-10-2022... In past years wide spaced Long Yagis were the number one choice for serious Terrestrial VHF/UHF DXing, those old designs created by adopting basic principles along with trial and error including a generous testing regime. The problem, they were mostly narrow bandwidth gain optimized designs subject to wet weather and close proximity effects, impacting on overall performance! To a certain degree mitigation could be effected by using a folded dipole (difficult to homebrew) driven element. Designed specifically for Terrestrial VHF/UHF DXing; Derek G4CQM presents a viable and simple split dipole solution, a selection of modernized VHF/UHF Low Q wide spaced Long Yagi designs optimized with K6STI's YO7 Professional version software and calibrated with NEC-2. Limitations associated with NEC-2 have been carefully avoided as there are no tapered or bent elements, no junctions, and no close proximity spacings. Unique element mounting clips designed by Derek avoid the need for correction by conforming to the DL6WU mounting directive. This requires that each element is raised more than the boom radius (r) above boom. A special tuning technique conceived by Derek gives rise to a low average Q-factor with subsequent wider bandwidth than older traditional designs, critical in delivering a stable antenna. From experience the very best designs occur when YO7's unique algorithm and NEC-2 concur. Advantages with these new Long Yagis; no matching, very easy to build, lightweight with low element density, and reliable performance. Finally, don't confuse these new designs with the OWA (Optimized Wideband Antenna) yagi concept which requires very close spacing between the DE (Driven Element) and D1. For kits and parts to build these designs contact G6HKS Yagi Kits & Parts for full details, specifications and prices. Just to be clear the DE requires 5/8th Inch (15.875mm) OD tube, whilst the parasitic elements are all 3/16th Inch (4.7625mm) OD rod. | MENU | BALUN | BUILD | PARTS | WS716464 | 4323WL50 | CQM3WL50 | 2M9N50LY | 2M8N50LY | 2M7N50LY | 2M6N50LY | 2M5N50LY | Special Builds | Old Vs New - Average Q-factor comparison and available bandwidth | |
2M7N50 old style gain optimized Long Yagi | New 2M7N50LY Low Q Long Yagi by G4CQM |
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2M7N50 140 - 150MHz | 2M7N50LY 140 - 150MHz |
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These graphs which compare old style 2M7N50 against the new 2M7N50LY design clearly demonstrate the relationship between average Q-factor and available bandwidth. Yagis have a frequency response similar to that of a low pass filter and so it is of paramount importance to keep the cut off frequency out of and above the desired passband. The prospect of high stability far outweighs any slight loss in forward gain when comparing designs, and the new low Q yagis offer a much greater degree of resilience when deployed in the real world! Software design limitations and construction tolerances are easily absorbed in the new low Q designs without any noticeable loss in overall performance. Understanding YO7 | |
1. Frequency 2. Forward Gain 3. Front-to-Rear Ratio 4. Input Impedance 5. Standing-Wave Ratio 6. Elevation Angle or Gain FOM |
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To reduce screen clutter, YO7 doesn't label the figures displayed within the Yagi patterns. They are shown in yellow font, 2M7N50LY example above. TOP ^ BUILDPlease carefully read the following notes... If you haven't built your own yagi before, construction guidance offered here will hopefully stop you making mistakes that will prevent your build from working as it should! These designs won't require any adjustment!
TOP ^ PARTS | |
Specialist and unique DE moulding and element mounting clips designed by G4CQM available from G6HKS Yagi Kits & Parts | |
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When founding PowAbeam Antennas way back in early 1994 I soon realised that unique and professional looking components would set my designs apart from the competition. Working as I did in the Telecommunications and Radio Communications industry I was fortunate to have access and be able to design the Driven Element moulding and specialist parasitic element mounting clips. TOP ^ WS716464 - 70cm Band (432MHz) 4.64λ 16 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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428 - 438MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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4 x WS716464 makes an ideal compact EME array with DL6WU stacking distances (H=1434mm V=1340mm) | |
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TOP ^ 4323WL50 - 70cm Band (432MHz) 3.02λ 10 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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428 - 438MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ CQM3WL50 - 2M Band (144MHz) 3.02λ 10 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ 2M9N50LY - 2M Band (144MHz) 2.52λ 9 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ 2M8N50LY - 2M Band (144MHz) 2.14λ 8 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ 2M7N50LY - 2M Band (144MHz) 1.68λ 7 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ 2M6N50LY - 2M Band (144MHz) 1.23λ 6 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ 2M5N50LY - 2M Band (144MHz) 0.8λ 5 Element Yagi | |
NEC-2 E-Plane Calibration | NEC-2 H-Plane Calibration |
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NEC-2 E-Plane | NEC-2 H-Plane |
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140 - 150MHz (Uncalibrated against NEC-2) | Elements: Positions, Lengths, Diameters |
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TOP ^ Legal
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