The DK7ZB-5-Band-Quad The DK7ZB-3-Band-Quad Oblong+Rhombus The Extended Oblong

 2-Element-DK7ZB-Quad for 5 Bands

10-12-15-17-20 m (updated version 01/2010 see down)

A description was in the German Ham-Magazine "Funkamateur" in Issue 11/2003.

The picture shows the quad, built by DL1DTC

The Quad uses a single, central-fed frame with a feeder-line. Therefore you must use an ATU for operating this antenna. Excellent would be a "Z-Match", a 1-KW-Tuner will be described on another page.

The reflector has one loop for each band, self-resonant without stubs.

The first DK7ZB-Quad was introduced in 1995 and contented a mistake and had not the best performance. In 2000 the Quad was optimized for 1-Lambda reflector loops with "EZNEC" by W7EL.

The basic principle of the radiator element is the Lazy-H (Pic. 2), a special form of a stacked array of two dipoles, which are fed with an open wire. The Lazy-H is a multiband-antenna with a low radiation angle an a bidirectional pattern and horizontal polarisation.

The points 1-2 and 3-4 have the same phase, therefore you can connect the ends together witout any disadvantage.

Pic. 3 shows this radiator element, which is no real "Quad" as you see above. This type of antenna was introduced first by DJ4VM. The full DJ4VM-Quad had two central fed elements with this design. It needed a double-matchbox with phasing-lines for the feeding and was difficult to built and more difficult to tune.

It is much easier to use separate parasitic reflector elements for each band and to tune only one frame with a simple ATU. So you get a Boomquad with an element-distance of 2,60 m.

Pic. 4: The 5 frames for the parasitic reflector, the distance between radiator and reflectors is 2,60 m.

Very important: The wires must have 1 mm diameter, with no insulation. I use copper-plated steel-wire ("DX-wire"). Simple copper will change the length in relation to the temperature!

Insulated wire must be 1-2% shorter, in relation to kind and thickness of the insulation (PE, PVC). In that case a new calculation of the lengths must be carried through!

Pic. 5 shows once more the basic principle of the 2-Element-Quad.

Because the frame on 10 m and 12 m is extended (Bisquare!), you get more gain than with a simple 1-Lambda-Quad.

Table 1 shows the mechanical dimensions, table 2 the electrical attributes for the 5 bands.

The mounting as "Diamond"-shape or "Quad"-shape has no influence on the electrical data. Both types are working with the same attributes.

 

The picture shows the Diamond-Quad of 

 Dave,  G0VXE

 

He reports from good results on 30 m. The antenna is working bidirectional only with the radiator-frame.

The only problem on 30 m is the low radiation resistance, in some cases this can cause troubles in the system feeder-ATU and additionel losses.

Table 1: Lengths of the wires (Boom 2,6 m)

Element

Circumference 

Side length 

Spreader (one half) 

Radiator-Loop

22,16 m

5,54 m

3,92 m

Reflector-Loop 20 m

21,96 m

5,49 m

3,88 m

Reflector-Loop 17 m

17,14 m

4,285 m

3,03 m

Reflector-Loop 15 m

14,72 m

3,68 m

2,60 m

Reflector-Loop 12 m

12,40 m

3,10 m

2,19 m

Reflector-Loop 10 m

11,48 m

2,87 m

2,03 m

  Table 2: Gain and F/B versus Frequency

Frequency

Gain in dBd

 F/B in dB

14,0

5,53

6,8

14,1

5,33

13,1

14,2

4,75

18,8

14,3

4,15

13,9

18,1

4,0

18,8

21,0

5,74

7,8

21,1

5,67

11,5

21,2

5,47

16,3

21,3

5,22

21,2

21,4

4,95

19,2

24,9

5,9

11

28,0

6,25

9,1

28,2

6,18

9,4

28,4

6,11

9,4

28,6

6,0

9,2

28,8

5,9

8,7

29,6

4,8

5,3

 

Updated version MK ll for better performance 

on all bands with a longer boom of 2,85 m

Lengths of the 2-mm-wires (Boom 2,85 m)

Element

Circumference 

Side length 

Spreader (one half) 

Radiator-Loop

22,00 m

5,50 m

3,89 m

Reflector-Loop 20m

22,00 m

5,50 m

3,89 m

Reflector-Loop 17m

17,20 m

4,30 m

3,04 m

Reflector-Loop 15m

14,72 m

3,68 m

2,60 m

Reflector-Loop 12m

12,48m

3,12 m

2,20 m

Reflector-Loop 10m

11,12m

2,78m

1,97 m

  Gain and F/B versus Frequency

Frequency (MHz)

Gain in dBd

 F/B in dB

10,1 0,8 1

14,0

5,5

7

14,1

5,4

13,5

14,2

5,0

30

14,3

4,6

17

18,1

5,5

21

21,0

6,1

11

21,1

6,0

14

21,2

5,8

17

21,3

5,7

17

21,4

5,5

15

24,9

6,2

14

28,0

6,2

9

28,2

6,2

10

28,4

6,3

11

28,6

6,2

12

28,8

6,2

13

29,0

6,2

13

29,5 6,1 12

Azimuth patterns (free space)