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QRP attenuator 50W / 5 W |
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I operate both QRO and QRP power
levels. My QRO power is 1kW and on QRP I run 5W. |
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As I have separate call signs for
QRO and QRP, OH1TV and OH1WX, I often work DX-speditions |
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with both calls. Threrefore I need
to adjust power levels quickly and often. But it is time consuming. |
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I have also tried separate rigs for
both powers. It is not convenient either. |
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So I decided to build this QRP
attenuator. My linear needs 50W drive,
that is, the exciter is adjusted to 50W. |
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By attenuating that 50W by 10 dB I
get 5W, by turning one switch. |
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On QRO I can have the full kW in the
other position of the switch |
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This attenuator acts like a negative
Linear Amplifier. |
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The schematics is very simple as you
can see. I built it from the parts I had in hand. |
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I had to connect two resistors in
series to get the needed resistance values. |
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The 10 pF capacitor was necessary in
order to improve impedance matching on the high end. |
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The measured attenuation was 10.2 dB
+/- 0.2dB over 1.8…52 MHz band. |
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Return loss is better than 20 dB on
50 ohm.. |
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The LED lights during QRP
transmission. |
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OH1TV |
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19.10.2007 |
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Back to projects page |
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