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ANTENTOP- 01- 2005, # 007  

Broadband Indoor Antenna

 

 

At that times I had a broadband transformer 9:1 from an old marine transmitter, the transformer worked good at 160- through 10 meters, but, unfortunately, the transformer had small sizes and it was very hot already at 50 Watts. Transformers made on a yoke ferrite core from 27” TV worked good at 200 Watts…

I experimented with antenna loads of 450 and 300 Ohms however, antenna with these loads was hard to match. 

 

Recently using MMANA (References 1) I simulated parameters of the antenna loaded to 600, 450, 300 Ohms.  For simplification it was supposed that the antenna is located in a free space. Table 1 shows the data.

Table 1 Data for broadband antenna

Band, meters

Gain, dB

SWR

600 Ohm

450 Ohm

300 Ohm

600 Ohm

450 Ohm

300 Ohm

160

-56

-56

-56

1.05:1

1.1:1

1.1:1

80

- 44

- 44

- 44

1.07:1

1.2:1

1.5:1

40

- 30

- 30

- 30

1.2:1

1.6:1

2.6:1

20

- 19

- 19

- 19

1.4:1

2.25:1

4.6:1

15

- 13

- 13

- 13

1.55:1

2.7:1

6.1:1

10

- 10

- 10

- 10

1.62:1

2.6:1

5.2:1

 

 

The table shows that the antenna has best SWR at 160 through 10 meters only at the 600 Ohm load. I can notice, that in real conditions, the antenna has SWR better then shown by the Table 1 because losses RF energy in the nearest subjects.

 

The table shows that the antenna is ‘dead’ at ranges 160 and 80 meters, but at good propagation you could make QSOs. Antenna gain is small at 40 through 10 meters too, but already even at rather average propagation (and 100 Watts in the antenna) I could easy make QSOs using the antenna.

 

MMANA shows that the antenna has one sided directivity, but I could not see that when I have used the antenna. See screenshots of the antenna simulated by the MMANA.

 

References

 

1. http://mmhamsoft.ham-radio.ch/

 

73! I.G.

 Broadband Antenna  in MMANA

http://mmhamsoft.ham-radio.ch/

 

http://www.antentop.org/

Page 61

 

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August 3, 2016 16:47

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