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Construction Details |
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All Yagis in 28-Ohm-Technology, elements mounted with polyamid-clamps (Konni)Electrical details on the pages you see above, construction with "YO 7" by K6STI and "EZNEC+4.0" by W7EL 430-440MHz at SWR <1,8 (10 El. 430-438) , Boom 15x15mm or 20x20mm, Radiator 10mm, Elements 8mm or 6mm
Photo: Collection of 70cm-28-Ohm-Yagis built by DJ8QV |
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Type |
Boomlength |
Gain (435MHz) |
F/B
(435MHz) |
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4-Element |
0,35m |
7,5dBd |
13dB |
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5-Element |
0,65m |
9,1dBd |
16dB |
| 6-Element | 0,85m | 10,1dBd | 20dB |
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7-Element |
1,00m |
10,5dBd |
30dB |
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9-Element |
1,50m |
12,0dBd |
26dB |
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10-Element |
2,00m |
13,0dBd |
35dB |
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Mounting of elements With these clamps the elements are mounted isolated 2-3mm above the boom. The screw has 3mm and is stainless steel. If you use other mounting methods, you must use the DL6WU-formula for boomcorrection! |
The boom correction uses the DL6WU-formula:
C = (12.5975-114.5 * B) * B * B
C=Correction factor for one element half (for full element x2) in wavelengths
B=Boom diameter in wavelengths
The following factors are for not-insulated mounting through the boom, if you mount the elements insulated through the boom (DJ9BV-method) or not-insulated above the boom, use the half correction factor.
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Boom |
10mm |
15mm |
20mm |
Element
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+3mm |
+ 7mm |
+ 11mm |
The parallel 75-Ohm-Cables for the DK7ZB-Match (see other Webpage!) Length Lambda/4*V V=Velocity of propagation e.g. for Full-PE (RG-59) is 0,67 Foam-PE 0,81-0,82, PTFE 0,7
Use a good cable with a high screening effectiveness! |
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Lengths of the 2x75-Ohm-Lambda/4-Cables for the DK7ZB-Match
Important: Use good quality cable, because cheap TV-cables have often not 75Ohm! Measurements show a resistance of 68, 70 and 80 Ohms for such cables...
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Type |
Full-PE |
Foam-PE, V=0,82 e.g. SATV-Cable |
Teflon
V=0,7 e.g.. RG-179 |
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Length |
115mm |
141mm |
120mm |
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The reflector, radiator and director 1 with the mounting box. The cable must be mounted symmetrically between the two element-halfs! |
| Another box with RG-179 PTFE-cable for the DK7ZB-Match |  |
