J-Pole antennas for 2m-40m with Wireman-cable

The picture shows the scheme of a J-Pole antenna. The high impedance feeding point of a l/2-wire (L1) is matched from some KOhms to a low impedance with a  l/4 matching sector (L2).

The point XX has an impedance of 50Ohm for direct feed with a coax cable. XX is  symmetrical, a choke or balun could be useful to avoid sleeve waves on the screen of the coax.

A very simple method for the  l/4-part is to use a 450-Ohm-Wireman cable. 

I have built up the antenna for 2m, 6m, 12m and 30m. The table gives the values for experimenting with the other bands.

L1=0,471l  (Halfwave-Radiator)   L2=0,223l  (Wireman-cable)    

Solder the braid of the 50-Ohm-coax at the left X, the inner conductor to the right X. XX about 5-10% of L2.

The antenna can be mounted in several ways:

The classic J-Pole with both sections mounted vertically.

Length 3/4-l,  only for the higher bands.

 

It is no difference in the radiating conditions, if the l/4-part is vertical or horizontal.

The pattern is identical with a vertical dipole.

Both parts horizontally mounted

The "Zepp"-configuration

The antennas were tested on 2m, 6m, 12m and 30m. The lengths for the bands marked with "*" have not been tested, try with he given dimensions. For other frequencies use the following fomulas for insulated 2mm-wires for L2. Not-insulated wires need a longer L2-section.

L1=0,471l  (Halfwave-Radiator)   L2=0,223l  (Wireman-cable)    

The points X-X are 5-10% from the shorted part of the Wireman-cable (look for best SWR).

For the 50MHz-J-Pole look on the special page:   50MHz-Halfwave-Verticals

Band

l/2- Wire  (insulated)

l/4- Wireman  V=0,905

XX

Fo MHz

SWR

Bandwidth SWR<1,5

40m*

20,02m

9,46m

73,0cm

7,05

-

100KHz

30m

13,96m

6,61m

58,5cm

10,12

1,1

150KHz

20m*

9,98m

4,73m

35,0cm

14,15

-

200KHz

17m*

7,80m

3,70m

26,5cm

18,1

-

250KHz

15m*

6,66m

3,15m

22,5cm

21,2

-

300KHz

12m

5,67m

2,67m

18,5cm

24,91

1,0

350KHz

10m*

4,96m

2,45m

15,5cm

28,5

-

500KHz

6m

2,815m

1,33m

6,5cm

50,15

1,1

1000KHz

2m

0,975m

0,47cm

3,5cm

145,2

1,0

1500KHz

The result of 10 Minutes work with the 12m-J-Pole, mounted on a fishing rod:

   

 

The 50MHz-J-Pole

see:

50MHz-Verticals