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Old computer's PSU gives useful parts for antennas

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ANTENTOP- 02- 2003, # 003

Old computer's PSU

Poor ham method of measuring of the efficiency

Table 6 Serial resistor and dissipated power at transformer's load

 Load resistance, Ohms 300 450 600 Resistance of the serial resistor, Ohms 84 (75) 234 (220) 384 (390) Dissipated power at transformer's load (the serial resistor plus the bulb), Watts 4.3 6.55 8.46

How to find the efficiency:

-                 A transmitter stands at a minimal RF power.

- Smoothly to increase the RF power of the transmitter.

-                 The load bulb should have the same glow like this one has at 26 volts d.c.

-                 In this case we make a decision, that, an RF voltage of 26 volts is acting across the bulb and an RF current of 0.12 amperes is going through the bulb.

Hence it is possible to calculate a power, which is dissipated at transformer's load (the bulb plus the resistor). Use Tab. 6 for this. The table shows a full

power, which is dissipated at transformer's load at a full glow the incandescent bulb.

The first stage in definition of the efficiency of the RF transformer is completed. Go to the second stage. We should find going an RF power to the transformer.

-                 Take attention to the incandescent bulb, which is bridged to the input winding, and fix (at your memory) its glow.

- Then do this bulb connected to a variable d.c. PSU (see Fig. 16B).

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