TWEENBOOM YAGI ANTENNAS FOR 144 MHZ
Slobodan Bukvic – Boban, YU7XL, yu7xl@mts.rs, http://www.qslnet.de/member/yu7xl/
Introduction
You have a small house yard and there is no room for a bigger antenna? A good answer could be the tweenboom antenna. The characteristics of a 10 m long yagi antenna can be achieved with a 6.5 to 7 m long tweenboom antenna. .
|
Fig. 1 - Antenna X21705XL1 under test |
This is an unusual approach to making high gain antennas. The idea is to build two vertically stacked yagi antennas, whose stacking distance is small.. The reflector, the radiator (and sometimes the first director) are common for both yagis. Some time ago I mentioned this antenna type in Dubus. Now I am going to describe such an antenna for 144 MHz.
Advantages
The small stacjing distance does not give a big increase in gain. It is usually around 1 dB over a single yagi (maximum 1.5 dB), but there are other benefits of such configuration.
As you can see, the booms should be slightly bent toward each other alongside for best performance. The vertical distance after bending is not critical, so a little error in bend is unimportant. However, the element distance/position is given on the centerline between the booms and should be projected vertically onto vertical projections on both booms precisely.
The Driven Element
I have designed many tween-boom antennas with open, folded or LFA radiators, but found the double quad the best shape of radiator. The antenna with such a radiator gives up to 0.5 dB additional gain in comparison to other radiator forms.
Construction
You might say this configuration is hard to build. No, it is not! Both booms strengthen each other, and both booms are additionally reinforced by mounting on a vertical frame holder. At the ends, both booms are finally squeezed to maintain the necessary boom curve, which gives some more strength. You can, even, use a very small diameter boom.
I built a 2.68WL (5.575 mm) long double boom yagi for 144 MHz using Ø25 mm soft Aluminium tubing, with 1 mm thick wall. Note that the 6 m long boom weighs just 1 kg. The gain is nearly 16 dBi. For such a gain, a classical Yagi would be 8 meters long - which means a much thicker boom tube, plus boom reinforcements.
I built the antennas with LFA radiators. Later I became aware that double quad performs better, so now I am preparing to replace LFA radiators with double quad ones.
The photos speak more than words. You can see my EME system which consists of four such antennas. I started working EME with them in October 2016 and it is too early to speak about experiences. However, I can compare them to my previous antennas, 16 x 9 ele hybrids, which were blown in June 2016 by a tornado (who sais there have never been tornados in my area?).
For me they are performing very well. The only drawback is the lack of XPOL, which is naturally not possible with this antenna type.
|
Fig. 2 - Four antennas stacked vertically at 5.00 meters and horizontally at 4.40 meters |
X21410XL7Q – ANTENNA DETAILS
|
Fig. 3. Layout of the X21410XL7Q antenna |
This is a small antenna, just 2.825 metres (1.36WL) long, but very efficient because its radiator is in the form of double quad. This allows a possibility of placing the antenna in front of support structure. The gain of 14.12 dBi gain is very respectable for such a short antenna. With classic yagis, this level of gain can be obtained with boom lengths of 2.0 λ or more. However, a 4.0 m long yagi usually cannot be placed in front of the stacking frame without ropes and other support components.
The radiator is made in the form of double rectangle. The middle horizontal rod has a 10 mm gap – for the feed points. Impedance at the feed point is 200 Ώ. That means that you have to use ½ λ balun to connect the 50 Ώ coax feed.
Boom correction have not been calculated. I suggest you use insulated elements, placed at least ten mm above the boom.
DIMENSIONS:
|
|
Ref |
De |
D1 |
D2 |
D3 |
D4 |
D5
|
D6 |
Dimensions given in milimetres Diameter of elements 10 milimetres No boom correction included. Height measured from centerline |
|
Position |
0 |
247 |
408 |
715 |
1096 |
1574 |
2258 |
2825 |
|
|
Length |
1016 |
806 |
919 |
921 |
935 |
915 |
899 |
889 |
|
|
Height |
0 |
±220 |
±235 |
±380 |
±510 |
±610 |
±665 |
±655 |
CONSTRUCTION OF RADIATOR
|
Fig. 4: – Sketch of the radiator (Ø= 10 mm, H = 806 mm, V = 220 mm). The 10 mm gap is for feeding the antenna |
COMPARISON (inserted in a part of VE7BQH table, where it belongs according to its boom length)
|
|
TYPE OF ANTENNA |
SINGLE ANTENA |
FOUR ANTENNAS IN H-STACK |
|||||||||
|
|
L (λ) |
GAIN (dBd) |
Z (ohms) |
VSWR Bandwidth |
E (m) |
H (m) |
Ga (dBd) |
Tlos (K) |
Ta (K) |
G/T (dB) |
||
|
|
X21410XL7Q |
1.36 |
11.97 |
199.1 |
1.08:1 |
3.88 |
3.38 |
17.25 |
3.0 |
236.4 |
-4.33 |
|
|
|
Vine 6 FD |
1.10 |
9.69 |
48.3 |
1.18:1 |
2.64 |
2.21 |
15.67 |
8.2 |
238.4 |
-5.95 |
|
|
|
G0KSC 6LFA |
1.13 |
9.69 |
49.3 |
1.04:1 |
2.60 |
2.19 |
15.64 |
4.0 |
236.9 |
-5.96 |
|
|
|
DD0VF 6 |
1.16 |
9.73 |
27.2 |
1.07:1 |
2.63 |
2.22 |
15.71 |
5.5 |
240.1 |
-5.94 |
|
|
|
M2 2M7 |
1.28 |
9.94 |
204.9 |
1.14:1 |
2.65 |
2.26 |
15.76 |
3.7 |
245.0 |
-5.98 |
|
|
|
G0KSC 7LFA |
1.39 |
10.62 |
48.0 |
1.19:1 |
2.84 |
2.49 |
16.53 |
1.8 |
248.9 |
-5.28 |
|
|
|
DG7YBN 7 |
1.44 |
10.59 |
47.2 |
1.70:1 |
2.88 |
2.47 |
16.55 |
4.5 |
242.7 |
-5.15 |
|
|
|
Vine 7 FD |
1.45 |
10.56 |
47.9 |
1.14:1 |
2.83 |
2.46 |
16.47 |
8.2 |
238.6 |
-5.16 |
|
|
|
G4CQM 7 |
1.50 |
10.76 |
50.7 |
2.31:1 |
2.89 |
2.53 |
16.69 |
7.9 |
239.9 |
-4.96 |
|
|
|
CT1FFU 7 |
1.54 |
10.82 |
28.0 |
1.02:1 |
2.87 |
2.50 |
16.70 |
2.8 |
237.7 |
-4.96 |
|
|
|
DK7ZB 7 |
1.57 |
11.11 |
28.4 |
1.64:1 |
3.16 |
2.84 |
17.13 |
5.8 |
272.6 |
-5.07 |
|
|
|
IK0BZY 6 |
1.63 |
11.11 |
19.5 |
2.27:1 |
3.10 |
2.77 |
17.04 |
4.8 |
266.5 |
-5.07 |
|
|
|
G4CQM 10 UZ2 |
1.67 |
10.74 |
45.1 |
1.26:1 |
2.89 |
2.51 |
16.68 |
5.7 |
235.9 |
-4.90 |
|
|
|
DG7YBN 8 |
1.68 |
10.94 |
47.5 |
1.16:1 |
2.91 |
2.56 |
16.84 |
3.5 |
238.8 |
-4.79 |
|
|
|
I4GBZ 7 |
1.69 |
11.41 |
48.4 |
2.27:1 |
3.18 |
2.86 |
17.26 |
5.7 |
278.9 |
-5.04 |
|
|
|
G0KSC 8LFA |
1.79 |
11.06 |
50.0 |
1.24:1 |
3.15 |
2.40 |
16.95 |
3.6 |
222.2 |
-4.37 |
|
|
|
W1JR 8 MOD |
1.80 |
11.14 |
50.0 |
1.14:1 |
3.07 |
2.75 |
16.99 |
5.3 |
256.7 |
-4.95 |
|
|
|
DJ9BV 1.8 |
1.80 |
11.34 |
77.5 |
1.34:1 |
3.16 |
2.80 |
17.28 |
5.5 |
261.2 |
-4.74 |
|
|
K1FO 10 |
1.84 |
11.34 |
29.4 |
1.44:1 |
3.10 |
2.78 |
17.27 |
4.3 |
257.7 |
-4.69 |
||
|
Vine 8 FD |
1.85 |
11.18 |
51.4 |
1.12:1 |
3.00 |
2.63 |
17.06 |
8.5 |
232.3 |
-4.45 |
||
|
YU7EF 8 |
1.87 |
11.31 |
48.5 |
1.21:1 |
3.04 |
2.71 |
17.23 |
3.8 |
242.1 |
-4.46 |
||
|
BQH8B |
1.88 |
11.60 |
50.0 |
1.29:1 |
3.28 |
2.97 |
17.62 |
7.2 |
259.3 |
-4.37 |
||
|
UR5EAZ 9 |
1.89 |
11.32 |
49.2 |
1.01:1 |
3.07 |
2.75 |
17.26 |
3.6 |
249.7 |
-4.56 |
||
|
G4CQM 8 |
1.91 |
11.52 |
49.5 |
1.11:1 |
3.15 |
2.83 |
17.45 |
5.1 |
248.5 |
-4.35 |
||
|
KF2YN Boxkite9 |
1.92 |
13.98 |
49.2 |
1.28:2 |
4.45 |
3.70 |
19.95 |
5.6 |
228.6 |
-1.48 |
||
|
CT1FFU 8 |
1.94 |
11.28 |
27.1 |
1.05:1 |
2.96 |
2.62 |
17.10 |
2.9 |
232.3 |
-4.41 |
||
|
G0KSC 8OWL |
1.95 |
11.63 |
48.9 |
1.26:1 |
3.13 |
2.82 |
17.55 |
4.6 |
235.7 |
-4.02 |
||
|
I0JXX 8 |
2.04 |
12.11 |
200.1 |
3.00:1 |
3.46 |
3.17 |
18.10 |
9.3 |
257.3 |
-3.86 |
||
|
DG0OPK 9 |
2.07 |
11.45 |
28.4 |
1.11:1 |
3.04 |
2.72 |
17.34 |
5.7 |
231.9 |
-4.16 |
||
|
DK7ZB 8 |
2.09 |
12.01 |
28.0 |
1.26:1 |
3.40 |
3.10 |
18.02 |
4.8 |
253.6 |
-3.87 |
||
|
G0KSC 9OWA |
2.09 |
11.99 |
49.1 |
1.30:1 |
3.33 |
3.04 |
17.96 |
4.9 |
247.0 |
-3.82 |
||
|
RA3AQ 9S |
2.12 |
12.04 |
47.1 |
1.08:1 |
3.35 |
3.06 |
18.02 |
4.7 |
246.5 |
-3.75 |
||
|
M2 9SSB |
2.12 |
11.96 |
200.6 |
1.26:1 |
3.33 |
3.04 |
17.92 |
10.8 |
245.9 |
-3.84 |
||
|
Z(ohms) - measured on 144.100 MHz Bandwidth – VSWR measured on 145.000 MHz |
||||||||||||
PERFORMANCE DATA:
|
Fig. 5: Radiation patterns for a single antenna (the value for gain not corrected) |
|
No of ele |
L (mm) |
G (dBi) |
F/B (dB) |
F/Sh (dBi) |
F/Sv (dBi) |
Hor (◦) |
Ver (◦) |
Temp (◦K) |
G/T (dB) |
Tlos (K) |
|
14 |
2825 |
14.12 |
28.06 |
- |
17.53 |
43.0 |
33.4 |
222.0 |
-9.35 |
3.3 |
WORKING CONDITION:
|
Frequency for SWR=1.5 (MHz) |
Z (Ώ) at 144.100 MHz |
SWR at 145.000 MHz |
||
|
Lowest |
Highest |
Bandwidth |
||
|
139.300 |
146.200 |
6.900 |
199.1 |
1.08:1 |
SWR DIAGRAMS (loss included for Al)
|
Fig. 6: SWR diagram for SWR = 1.5 (losses included for Al) |
|
Fig. 7: SWR diagram from 144 to 146 MHz (losses included for Al) |
STACKING
The tweens stack very well. Use the following stacking distances, because some different distances can produce quite unwanted results! If you need to use other distances, please, send me an e-mail and we will find the best solution.
TWO ANTENNAS IN VERTICAL STACK
|
|
Distance (mm) |
Gain (dBi) |
TA (K) |
Tlos(K) |
G/T (dB) |
|
Per DL6WU formula |
3620 |
17.13 |
222.4 |
3.3 |
-6.34 |
|
For lowest temperature |
3620 |
17.13 |
222.4 |
3.3 |
-6.34 |
|
For highest G/T |
3680 |
17.15 |
222.7 |
3.3 |
-6.33 |
FOUR ANTENNAS IN VERTICAL STACK
|
|
Distance (mm) |
Gain (dBi) |
TA (K) |
Tlos(K) |
G/T (dB) |
|
Per DL6WU formula |
3620+3620+2620 |
20.14 |
221.8 |
3.3 |
-3.32 |
|
For lowest temperature |
3380+3380+3380 |
19.99 |
217.8 |
3.3 |
-3.39 |
|
For highest gain |
3680+3680+3680 |
20.17 |
223.4 |
3.3 |
-3.32 |
|
For highest G/T |
3620+3620+2620 |
20.14 |
221.8 |
3.3 |
-3.32 |
TWO ANTENNAS IN HORIZONTAL STACK
|
|
Distance (mm) |
Gain (dBi) |
TA (K) |
Tlos(K) |
G/T (dB) |
|
Per DL6WU formula |
2838 |
17.01 |
225.8 |
3.3 |
-6.53 |
|
For lowest temperature |
1420 |
15.78 |
216.7 |
3.3 |
-7.58 |
|
For highest G/T |
3800 |
17.15 |
221.0 |
3.3 |
-6.30 |
FOUR ANTENNAS IN H - STACK
|
|
Horizontal distance (mm) |
Vertical distance (mm) |
Gain (dBi) |
TA (K) |
Tlos (K) |
G/T (dB) |
|
Per DL6WU formula |
2838 |
3620 |
20.04 |
226.9 |
3.3 |
-3.52 |
|
For lowest temperature |
1420 |
3620 |
18.79 |
214.4 |
3.3 |
-4.52 |
|
For highest G/T |
3800 |
3680 |
20.19 |
221.7 |
3.3 |
-3.27 |
|
Fig. 7: Radiation patterns for four antennas in H-stack (the value for gain not corrected, H = 3.8 m, V = 3.68 m ) |
SIXTEEN ANTENNAS IN H-STACK
|
|
Horizontal distance (mm) |
Vertical distance (mm) |
Gain (dBi) |
TA (K) |
Tlos (K) |
G/T (dB) |
|
For lowest temperature |
1420+3800+1420 |
3620+3620+3620 |
24.81 |
213.1 |
3.3 |
+1.52 |
|
For highest G/T |
3800+3800+3800 |
3680+3680+3680 |
26.23 |
221.5 |
3.3 |
+2.77 |
|
Fig. 11: Layout of the stack of 16 antenna |
|
Fig. 9: – Radiation patterns for sexteen antennas in H-stack (the value for gain not corrected, H = 3.80+3.80+3.80 m, V = 3.62+3.62+3.62 m ) |
|
Fig. 19: – Radiation patterns for sexteen antennas in H-stack (the value for gain not corrected, H = 1.42+3.80+1.42 m, V = 3.68+3.68+3.68 m ) |
CONCLUSION
This antenna is made of Al tubing Ø10 mm. Also available are versions with other boom diameters (5, 6 or 8 mm, or inch sizes). Just send me an e-mail if you need something different from the versions presented here. Also, if you make this antenna, please, send me your experiences and photos. Thank you.
You won`t be dissappointed with this antenna building, I am sure. Good DX!
Slobodan Bukvic, YU7XL