 |
144,3 MHz, single Yagi: Boom 6,88 m Gain 13,46 dBd F/B > 32 dB Ta = 223,6 K G/T = - 7,92 dB |
| Design principles | 5-El.-2-m-OWM-Yagi | 8-El.-2-m-OWM-Yagi | 8-El.-2-m-OWL-Yagi | 11-El.-2-m-OWL-Yagi | 14-El.-2-m-OWL-Yagi |
| Design study V-Yagis |
Ultra-Low Noise optimized 50-Ohm-Yagis
Design studies on two YU7EF-Yagis
| Because the original YU7EF-Yagis have the optimum director
dimensions for a low-noise concept it would be interesting to see how
these director chain could be combined with other design principles for
further improvements. What would be better as to take the original
designs?
In the first step I investigated if an impedance of 28 Ohm could be a better choice as the standard 50 Ohm, because my simulations in the last 20 Years showed that in all cases the medium impedance gives a better performance. The reason is the better F/R in relation to 50-Ohm-Yagis. In the second step the stretched 28-Ohm-radiator was replaced by a V-radiator as described on the principles page. The results in both cases were really surprising. Both steps could improve the data of the Yagis. That shows that the combination of the YU7EF-low-noise-concept with the V-Dipole would be the perfect solution for Ultra-Low-Noise-Yagis. Here are the results for the EF0212B in a short summary. For your own investigations here the EZ-Files for EZNEC or 4NEC2 as download. |
|
Type |
Gain |
Ta |
G/T |
SWR
at 145Mhz |
Download EZ-file |
|
EF0212B-50
(orig.) |
13,41
dBd |
226,6 K |
-
8,01 dB |
1,16 |
EF0212B-50 |
|
EF0212B-28
(See file) |
13,36
dBd |
222,4 K |
- 7,99
dB |
1,13 |
EF0212B-28 |
|
EF0212B-50-V |
13,46
dBd |
223,6 K |
- 7,92
dB |
1,21 |
EF0212B-50-V |
12-El.-Yagi EF2012B modificated for 50 Ohm-V
|
144,3 MHz, single Yagi: Boom 6,88 m Gain 13,46 dBd F/B > 32 dB Ta = 223,6 K G/T = - 7,92 dB |
The data for a 4-bay-array are better than a LFA-Yagi with the same length:
Here the impressive patterns for the 12-El.-V-Yagi
 |
|
|
The schema of the Yagi |
Elements 8 mm, radiator 10 mm diameter
| Element | Ref | Rad | D 1 | D 2 | D 3 | D 4 | D 5 | D 6 | D 7 | D 8 | D 9 | D 10 |
| Position | 0 mm | 235 mm | 420 mm | 775 mm | 1315 mm | 1960 mm | 2715 mm | 3530 mm | 4385 mm | 5265 mm | 6155 mm | 6880 mm |
| Length | 1018 mm | see down | 949 mm | 942 mm | 920 mm | 904 mm | 889 mm | 876 mm | 866 mm | 850 mm | 847 mm | 849 mm |
The table with positions and lengths
10-El.-Yagi EF2010LT modificated for 50 Ohm-VV
| With a bent radiator is the excellent basis of the EF0210LT the reason for unbelievable patterns. For reducing the unwanted radiation +/- 90° D 1 was bent, too. The director chain cannot be optimized, but the F/R is improved. |
|
Type |
Gain |
Ta |
G/T |
SWR-Min. |
SWR
at 145Mhz |
Download EZ-file |
EF0210LT |
11,87
dBd |
224,5 K |
-
9,52 dB |
144,5 MHz |
1,12 |
EF0210LT |
EF0210LT-VV |
12,05
dBd |
223,3 K |
- 9,31
dB |
144,3 MHz |
1,3 |
EF0210LT-VV |
 |
Element lengths and positions |
 |
 |
