Archive of low Q VHF/UHF yagi designs
by Derek Hilleard G4CQM (2017)
A superior range of AOWA yagi designs by Derek Hilleard G4CQM (2017)
SCQM70UC 70 element 1296MHz compact AOWA built by John Lemay G4ZTR
- All weather high performance AOWA yagis for 50/70/144/432MHz... Average Q-factor <25
- For -3dB beamwidth (BW) see tables below and/or click onto Vertical & Horizontal Plane images
- Build dimensions and optimal/precise stacking distances see .nec files
- The following presentation was carried out using the free and powerful 4nec2 by Arie Voors
- Designs conceived/validated in K6STI's YO7 & AOP professional versions software
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BUILD
Please 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!
- Boom size
High Band featured designs require 3/4 Inch (19.05mm) square section aluminium, and use heavy wall gauge for strength. However, some form of overhead or underside bracing is required for the very longest booms. Meanwhile Low Band designs will require a larger boom size of 1 Inch (25.4mm) square or above.
- Element size
High Band parasitic elements require 3/16 Inch (4.7625mm) diameter solid rod whilst the DE 5/8 Inch (15.875mm) is tube. However, those Low Band designs listed will use different size tubing for the elements. It is very important therefore to double check the .nec files to ascertain the correct build dimensions.
- Measuring
Lay out boom, mark position of reflector element, measure all other element positions from this point.
Aim for the nearest mm!
- Tolerances
Measure and cut the parasitic elements to the nearest mm. However, it is better to cut them 1mm too short than 1mm too long. Reason: Yagis have a frequency response similar to a Low Pass Filter so it is very important to keep the cut off frequency out of and above the desired pass band.
- Element Mounting
ALL DIMENSIONS ARE FREE-SPACE
ELEMENTS NEED TO BE INSULATED FROM AND RAISED SUFFICIENTLY HIGH ABOVE THE BOOM TO AVOID BOOM CORRECTION AS PER DL6WU MOUNTING DIRECTIVE! I.E. RAISED MORE THAN THE BOOM RADIUS (r) ABOVE THE BOOM...
No boom correction is required if you follow this advice!
- Boom Correction
Specialist element mounting clips designed by G4CQM available from G6HKS Yagi Kits & Parts don't require correction!
- End Caps
Avoid using plastic, vinyl, or rubber end caps on any of the elements (reflector, driven and directors), these will affect tuning and make wet weather performance worse! Seal the DE with flush mounting end plugs.
- Driven Element
The DE length is end to end which must include the centre gap of 15mm!
Example 2M7N50LY - From the YO7 elements table the driven element total length is 481.5mm x 2 = 963mm. To achieve this in practice deduct the center gap dimension of 15mm from the total, and cut a length of tube to 948mm. Finally, cut this into two pieces, each will then be 474mm in length!
- Boom length
Allow an additional +30mm at either end of the boom to maintain tuning across its entire length, and also give a professional look...
Example: 2M7N50LY Reflector to D5 spacing is 3478mm + 30mm + 30mm = 3538mm BOOM LENGTH!
- VSWR
It is unlikely that reflected power will be exactly 1:1 in the operational bandwidth, a small amount of reflected power is normal due to software limitations and construction tolerances... Don't tune with your test equipment, use as a guide/reference only!
- WARNINGS
DOUBLE CHECK YOUR MEASUREMENTS BEFORE YOU CUT & DRILL!
DON'T ALTER THE DESIGN IN ANY WAY I.E. NUMBER OF ELEMENTS, LENGTHS, DIAMETERS OR POSITIONS. IF BUILT CORRECTLY THESE DESIGNS WON'T REQUIRE ANY ADJUSTMENT...
Finally... When stacking beam antennas using a power splitter to feed them, all of the dipoles need to have the same polarity, identify the live side with red tape!
6M (50MHz) Band
| Design | λ | Boom (m) | BW Az° | BW El° | Gain (dBi) | F/B (dB) | DE | Q |
|---|
| 6CQM5UC | 0.47 | 2.8 | 60 | 92 | 8.64 | 17.0 | SD | 6.3 |
| WS65055 | 0.55 | 3.305 | 60 | 80 | 9.34 | 17.2 | SD | 6.69 |
| WS65065 | 0.65 | 3.9 | 56 | 80 | 9.59 | 20.7 | SD | 4.3 |
| 6CQM6UX | 0.71 | 4.26 | 56 | 72 | 10.3 | 22.9 | SD | 21.69 |
| WS66075 | 0.75 | 4.5 | 52 | 72 | 10.4 | 20.6 | SD | 22.11 |
| WA66080 | 0.80 | 4.8 | 52 | 64 | 10.9 | 17.6 | SD | 15.56 |
| WS66082 | 0.82 | 4.9 | 52 | 68 | 10.7 | 20.9 | SD | 8.8 |
| WS67116 | 1.16 | 6.95 | 48 | 56 | 12 | 25.9 | SD | 15.1 |
| PA0712L | 1.23 | 7.35 | 44 | 52 | 12.2 | 21.5 | SD | 16.3 |
| WS68162 | 1.62 | 9.672 | 40 | 48 | 13.2 | 24 | SD | 15.3 |
4M (70MHz) Band
| Design | λ | Boom (m) | BW Az° | BW El° | Gain (dBi) | F/B (dB) | DE | Q |
|---|
| 4CQM5UC | 0.47 | 2.009 | 60 | 92 | 8.67 | 16.9 | SD | 5.18 |
| WA45055 | 0.55 | 2.360 | 56 | 80 | 9.4 | 17.1 | SD | 5.27 |
| WS45065 | 0.65 | 2.784 | 56 | 80 | 9.6 | 20.8 | SD | 4 |
| WS46075 | 0.75 | 3.212 | 52 | 72 | 10.4 | 20.3 | SD | 18.2 |
| WS46082 | 0.82 | 3.498 | 52 | 68 | 10.7 | 20.7 | SD | 7.39 |
| WS47116 | 1.16 | 4.9 | 48 | 56 | 11.7 | 25.9 | SD | 20.02 |
| PA0712H | 1.23 | 5.247 | 44 | 52 | 12.2 | 21.7 | SD | 10.7 |
| WS48179 | 1.79 | 7.651 | 40 | 44 | 13.5 | 19.4 | SD | 4 |
2M (144MHz) Band
| Design | λ | Boom (m) | BW Az° | BW El° | Gain (dBi) | F/B (dB) | * Ta (K) | * G/Ta | DE | Q |
|---|
| WS25065 | 0.65 | 1.354 | 56 | 80 | 9.54 | 19.6 | 298.7 | -9.16 | SD | 3.51 |
| WS26075 | 0.75 | 1.565 | 56 | 72 | 10.3 | 22.4 | 230.3 | -7.53 | SD | 21.5 |
| WS26082 | 0.82 | 1.700 | 52 | 68 | 10.6 | 21.9 | 237.8 | -7.18 | SD | 10.27 |
| WS27116 | 1.16 | 2.417 | 48 | 56 | 12 | 27.4 | 233.1 | -5.96 | SD | 17.7 |
| WS27123 | 1.23 | 2.550 | 44 | 56 | 12.1 | 25.6 | 233.6 | -5.80 | SD | 10.19 |
| WS28162 | 1.62 | 3.357 | 40 | 48 | 13.1 | 26.7 | 232.6 | -4.95 | SD | 17.4 |
| CQM8C4 | 1.68 | 3.480 | 44 | 52 | 12.8 | 26.7 | 229.4 | -4.98 | SD | 11.3 |
| WAXX8S | 1.79 | 3.725 | 40 | 44 | 13.4 | 19.8 | 243.6 | -4.61 | SD | 4.57 |
| WA9XX | 1.79 | 3.725 | 40 | 48 | 13.1 | 24.8 | 228.2 | -4.55 | SD | 19.76 |
| CQM9C4 | 2.13 | 4.428 | 40 | 44 | 13.7 | 28.2 | 230.6 | -4.11 | SD | 9.4 |
| CQM12UX | 2.34 | 4.835 | 40 | 44 | 14.1 | 23.1 | 228.8 | -3.76 | SD | 5.6 |
| CQM10C4 | 2.36 | 4.890 | 38 | 42 | 14.1 | 25.6 | 222.26 | -3.84 | SD | 15.3 |
| CQM0211 | 3.00 | 6.238 | 32 | 36 | 15.2 | 34.9 | 226.7 | -2.40 | SD | 23.89 |
| 144NX13S | 3.85 | 7.980 | 32 | 32 | 16.0 | 27.7 | 218.3 | -1.57 | SD | 23.9 |
| 144NX14 | 3.85 | 7.980 | 32 | 32 | 16.0 | 37.5 | 221.7 | -1.58 | SD | 18.7 |
| XX14 | 4.0 | 8.3 | 28 | 32 | 16.2 | 31.4 | 221.4 | -1.41 | SD | 18.6 |
| WS215446 | 4.46 | 9.25 | 28 | 32 | 16.5 | 28.3 | 223.4 | -1.27 | SD | 10.2 |
70cm (432MHz) Band
| Design | λ | Boom (m) | BW Az° | BW El° | Gain (dBi) | F/B (dB) | * Ta (K) | * G/Ta | DE | Q |
|---|
| 4323WL50 | 3.0 | 2.092 | 32 | 36 | 15.3 | 30.2 | 36.4 | 5.63 | SD | 16.4 |
| WS715446 | 4.46 | 3.093 | 28 | 28 | 16.7 | 28.2 | 34.1 | 7.33 | SD | 9.2 |
| WS718562 | 5.62 | 3.9 | 28 | 28 | 17.5 | 32 | 30.7 | 8.52 | SD | 21.7 |
23cm (1296MHz) Band
| Design | λ | Boom (m) | BW Az° | BW El° | Gain (dBi) | F/R (dB) | DE |
|---|
| SCQM70UC | 20.65 | 4.778 | 14 | 14 | 22.64 | 32.41 | SD |
| Explanations: |
|---|
| Note * = 4 x Yagis (f = 144.1MHz or 432.1MHz) |
| T_sky and T_earth values as per original VE7BQH Antenna Tables |
| Elevation angle °30 proposed by DJ9BV |
| Q = Q-factor average over a selected 2MHz bandwidth |
| Some alternative or special element sizes available, check .nec files! |
| SD = Split Dipole |
Useful External Links
1. Arie Voors powerful and truly excellent 4nec2 free NEC based antenna modeler and optimizer
2. BADLAND BRACKETS, HIGH FREQUENCY & VHF ANTENNA ACCESSORIES
3. Contest and DX Library by KA9FOX Software for Contesters and DXers
4. K6STI 88-108 MHz
5. Pat W0OPW Nec2Go Nec2 modeling by equation!
6. Richard Mason G6HKS Yagi Kits & Parts
7. Steve (G0UIH/VK2IAY/3D2FI) q82.uk antenna homebrewers and experimenters website
Terms and conditions
- These yagi antenna designs aren't for commercial use of any kind without prior consent!
- Private experimenters are free to use these designs for their own personal enlightenment. However, no guarantee or warranty is offered or implied.
- 2021 theme by Derek Hilleard G4CQM - Hand coded with Pluma text editor and Ubuntu MATE 20.04.2 LTS - Copyright © 2021 All Rights Reserved
- THIS WEBSITE DOESN'T USE COOKIES, EXTERNAL LINKS MIGHT!
