The DK7ZB-5-Band-Quad The Oblong The Extended Oblong

 2-Element-DK7ZB-Quad for 5 Bands

10-12-15-17-20m

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 1KW-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 tune.

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

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

Very important: The wires must have 1mm 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% longer, 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 10m and 12m 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 30m. The antenna is working bidirectional only with the radiator-frame.

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

Table 1: Lengths of the wires

Element

Circumference 

Side length 

Spreader (one half) 

Radiator-Loop

22,16m

5,54m

3,92m

Reflector-Loop 20m

21,96m

5,49m

3,88m

Reflector-Loop 17m

17,14m

4,285m

3,03m

Reflector-Loop 15m

14,72m

3,68m

2,60m

Reflector-Loop 12m

12,40m

3,10m

2,19m

Reflector-Loop 10m

11,48m

2,87m

2,03m

  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