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.
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-
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