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

The Extended Oblong for the Shortwave Bands

 

The 1-λ-Oblong has a gain of 2,6 dBd. We can increase the gain with a greater circumference.

The highest gain with 3,6 dBd will be in the case of 1,32 λ length and a relation of the sides of 0,16 : 0,5 λ. The feedpoint impedance is 72 + j 660 .

Therefore we need a matching network. Better is an ATU and the feeding with a Wireman-twin-cable. In that case we can use the extended Oblong for more than one band. An example for such an antenna is shown right.

This is an extended Oblong for 24,9 MHz. The antenna can be used for 10m, 15m and 17m, too.

Band

Gain

Impedance

28 MHz

3,17 dBd

580 + j 2600

24,9 MHz

3,67 dBd

55 + j 500

21 MHz

2,99 dBd

24 +/- j 0

18,1 MHz

1,4 dBd

19 j 270 

The table shows the gain and the impedance at XX for the 24,9-MHz-Extended Oblong. Feeding with Wireman-cable and an Antenna-Tuner.

As a support a glass-fibre mast or a metallic mast can be used, mount the wires insulated!

The elevation plot above real ground with medium conductivity. The antenna is mounted 5 m above the ground with the lower part of the loop.

Band

Height 5 m above ground

Height 10 m above ground

10 m

7,51 dBd

15

8,35 dBd

10

12 m

7,51 dBd

19

8,67 dBd

12

15 m

6,8 dBd

22

7,79 dBd

15

17 m

5,75 dBd

25

7,03 dBd

17