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Modified Beverage Antenna

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ANTENTOP- 01- 2016 # 020

Modified Beverage Antenna

 

 

Wire wound resistor (that was for the termination load is used) is used for DC current limitation circuit and is not intended for RF application. The resistor has some significant reactance at RF. However the resistor has 5- Watt of dissipation power. So all together for the load it was at least 50- Watts. At my experimenters such one resistor could stand dissipation power up to 20- Watts. Resistor was very hot but not burned. Well then I could not worry about my 100 Watts going in to antenna. But how would work the Beverage antenna with the wire wound resistor? Anyway only experiment could show me the result. I took flashlight put on coat and went with the new load to my antenna.

 

In spite of cold (minus 7 C degree, minus 15 with wind) and snow it not took long time to change burned termination resistor to a good one. In my Beverage Antenna the antenna wire and ground wire are connected to the termination load with help of an electrical automotive screw (bought it in Home Depot). So it took for me a moment to change the load.

 

If you look attentively at the burned load you may see that resistors from the load were burned out not evenly. Some resistors have burned out resistive lay in length in 1- 2- mm across them. Other resistors are almost black with burned resistive lay in circle or two circles of the resistors. There are completely burned out resistors. It is typical condition of a burned termination load of a Beverage Antenna. I explain why it is this way.

 

When termination load is overload at the beginning firstly electrically weak resistors are burned out. At the next key down RF voltage at the antenna end would be increased (because some resistors are opened and summary resistance of the termination load is higher the 450- Ohm). Then it would be burned out the second parts of the resistors of the termination load. However while the voltage is increased the resistors are burned out more intensively. Then when we press key down the several live resistors would get to much RF voltage that finally destroyed at all the last live resistors. With each pressing down key the damage for live resistors would be sever compare to the first burned out ones.

 

Electrical Automotive Screw

 

 

Burned Termination Resistor

 

I made measurement of the antenna with wire wound termination load with help of SWR- Meter of the IC- 718 and with help of MFJ- 259B. Table 3 shows SWR of the Beverage Antenna with wire wound termination measured by IC- 718. Table 4 shows SWR of the Beverage Antenna with wire wound termination measured by MFJ- 259B. MFJ- 259B does not indicates the character of the reactance (capacitance or inductive) so I used sign @ at the reactance.

 

Table 3

Beverage Antenna with LDG Transformer Loaded to Bridge of 10 Wire Wound Resistors (overall resistance: 440 Ohm). Length of the 50- Ohm Coaxial Cable to antenna is 50. Measurement by IC-718

 

Band

160

80

40

30

20

17

15

12

10

SWR

 

1.4

1.0

1.2

1.1

1.0

1.5

1.4

1.6

2.2

 

 

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Last Updated:

April 2, 2016 22:49

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