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5-Element-12,5-Ohm- Yagi with 6m-Boom Short data: Gain 9.6 dBd, F/R >28 dB, bandwidth > 300 KHz (50.0-50.3 MHz) at SWR < 1.5
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| 4-El-12,5-Ohm (2,90 m) | ||
| 5-El-12,5-Ohm (6,00 m) | ||
| 7-El.-28+50Ohm (9,20+7,75 m) | 8-El.-28-Ohm (12,30 m) | 9-El.-28-Ohm (14,00 m) |
| 4-El-28+50-Ohm (2,20 m) | 5-El-50-Ohm (4,30 m) new | 6-El-50-Ohm (6m+7,20 m) new |
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5-Element-12,5-Ohm- Yagi with 6m-Boom Short data: Gain 9.6 dBd, F/R >28 dB, bandwidth > 300 KHz (50.0-50.3 MHz) at SWR < 1.5
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2x5-Element-12,5Ohm stacked Gain 12,3 dBd left: built by Tom, DK3EE
right: MM0CPS/GM2T built by Colin, GM0RLZ |
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updated data 16-May-2008 for better matching
| Element | Position | Length (12 mm) | Length (10 mm) |
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Ref |
0mm |
2980mm |
2980mm |
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Rad |
760mm |
2846mm |
2850mm |
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D1 |
2140mm |
2712mm |
2718mm |
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D2 |
4275mm |
2680mm |
2700mm |
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D3 |
5970mm |
2610mm |
2630mm |
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Match with a choke made of 2x Lambda/4 50-Ohm-coax in parallel to a grounded socket, feedpoint impedance 50 Ohm. An other construction for the radiator is a folded dipole with an impedance of 50Ohm (4x12.5Ohm). At the feedpoint use a toroid balun 1:1 (T 200-6) to match the symmetrical load to the coax-cable. |
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In the last time it comes into fashion to compare
"old" and "new" designs by other designers. Normally
I would not share this discussion, but in this case I must make an
exception.
G0KSC claims his 1-lambda 50-MHz-LFA as much better. Indeed the LFA has a greater bandwidth (which you do not need for CW/SSB/beacons). The LFA has a better pattern ("Low-Noise"), especially the bigger vertical sidelobes of the DK7ZB-Yagi are criticized. But in the real world you have no free-space conditions. If you mount the Yagi above real ground, the sidelobe disappears by ground reflection influence (see picture down). Do you believe the upper sidelobe, pointed into the sky receives any "mystic" noise (from aliens, or what)? Or the horizontal forward sidelobe with is suppressed -25 dB? Now compare the gain of the two Yagis with the same boomlength: 5-El.-DK7ZB 9,6 dBd, 5-El.-LFA 8,9 dB |
| In the real environment you cannot see anything from a sidelobe
pointed downwards !
But a difference of 0,7 dB gain for the same boomlength of 1 lambda is a really big one. 22 years of my own DX-experience on 6 m show the effectivity of these high-gain Yagis. The simple to built 5-El.-Yagi is still a good choice and in use by several successful DX-stations!
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