Spring will slowly wake up and it will pull us out on the hills again, for nature, but certainly behind the broadcast. You may be thinking of a new antenna. Then make the following lines from Zoli OM7AQ stimulating.
The term QUAGI is a compound, which consists of the words Quad and Yagi. The Quagi antenna is also a compound, because it is made of Quad and Yagi antenna elements. The directors are from Yagi, radiator and spotlight from quad. Quagi antennas have been used in several versions – 8 and 11-element at 2m, 15 and 18-element at 70cm and 15-element at 23cm. W5UN uses for EME experiments on a 2m longer modification. In this article I will describe the 11-element version of 144 MHz and as an interesting 15-element Quagi on 1296 MHz.
As a beam for this antenna (obr.1) we will use an armored or AlMgSi pipe with a diameter of 20 mm. All elements are mounted isolated from the beam. The directors have a diameter of 6 mm and are made of aluminum or AlMgSi. Spotlight and radiator (obr.2) are made of Cu or Al wire with a diameter of 4mm. When you use copper, so don't forget to protect against oxidation by painting it. A mechanically strong material must be used for the support brackets for the reflector and radiator, whose dielectric properties must be as good as possible.
We can supply the antenna directly with coaxial 50 ohm. PSV would be in the range 144 – 146 MHz should not exceed 1,5. In the case of a worse PSV, we can try to move D1 towards the radiator. The dimensions of the antenna are given in the table.
Dimensions 11-el.Quagi on 144 MHz (v mm):
R (circuit)
2209
T
10
Ž (circuit)
2088
A1
533
D1
919
A2
394
D2
913
A3
838
D3
904
A4
787
D4
900
A5
787
D5
894
A6
803
D6
889
A7
914
D7
884
A8
914
D8
884
A9
864
D9
881
A10
876
15 el.Quagi na 1296 MHz
Quagi for 23cm (obr.3) I used a PVC pipe 1/2″. The elements are made of Cu wire with a diameter of 3 mm. We drill the beam and fasten the directors with a suitable glue. The diagram of the radiator is shown in Fig.4. The reflector and radiator mounting brackets must be made of an insulating material with the best possible dielectric properties. We supply the antenna with low-attenuation (!) coaxial 75 ohm. Again, surface protection of copper elements against oxidation is important. The dimensions of the antennas are in the table.
Dimensions 15-el.Quagi on 1296 MHz (v mm):
R (1 page)
61,0
A1
60
Ž (1 page)
58,5
A2
51
D1
99,0
A3
93
D2
98,5
A4
50
D3
98,0
A5
74
D4
97,0
A6
74
D5
96,5
A7
74
D6
96,0
A8
102
D7
95,0
A9
102
D8
94,5
A10
95
D9
94,0
A11
97
D10
93,0
A12
78
D11
92,5
A13
105
D12
92,0
A14
116
D13
91,0
Experiences
For many years I used a Quagi antenna on 144 MHz. The antenna also proved its worth in DX operation. I followed her up with Es, MS, Aurora and tropo connections to more than 100 large locators.
In the OM3KKF radio club (contest brand OM7F) 2x8el.Quagi antenna system at 2m proved to be good for us at the transient QTH Poľana.
I can recommend Quagi to everyone, who wants to be relatively small, but a powerful antenna and likes to experiment in the field of VHF.
Literature
[1] József Hetves, HA7PR: 11elemes Quagi antenna 2m-re; CQ HA 2/1992
[2] Dr.Kahle Frigyes, HA5KF: Quagi antennas; Radio engineering 1980
