Design your own 50 ohm "power attenuator" with this excellent and unique Power Attenuator Calculator.
A power attenuator is an attenuator, which is suitable for a much higher input power than is usual for an simple Pi-type attenuator.
The three fundamental resistors that form a Pi-type power attenuator, are each composed of a number of resistors in parallel.
The power is distributed across the resistors.
The higher the power, the more resistors are required.
The calculator enables you to take good available resistors of a modest power.
So you don't have to use "unavailable" high power resistors .
Just use carbon resistors. They are induction free. Don't use wirewound resistors.
The Calculator will calculate the resistors effortlessly.
The calculator computes the number of resistors and the values of the resistors, which are based on the E12-series values.
Due to the good availability and your own choice of the maximum power of the resistors (e.g. 1/2 watt), you can get exactly what you want.
The use of this unique Power Attenuator Calculator eliminates the need for high power resistors, to build a power attenuator.
Don't care about the number of resistors needed. 5 Resistors of 1/2 W will take about the same space as 3 resistors of 1 W.
With three or more resistors in parallel, just twist the leads of the resistors together.
Finally you can get less power from your QRP set, when 5 watts is the lowest power of the set.
With the Power Attenuator Calculator, you can design an attenuator for any input power.
How to use the Calculator.
1) Choose the attenuation, 3 dB, 10 dB or 20 dB. Preferably use Tab to enter the values and to move to the next (white) input field.
2) Enter the input power [Tab]   (e.g. 5 watt)
3) Enter the maximum power of the resistors [Tab]   (e.g. 1/2 watt - Enter 0.5)   Use a comma as decimal indicator in the Dutch version of Excel (0,5)
There is no RUN button, because the spreadsheet will calculate all values immediately, each time an input value is changed.
The Calculator has NO limitations on the input power or the maximum power of the resistors.
The Calculator will even work with an input power of more than 5 watts or with resistors of 0.25W or 0.1W. hi.
Download the Power Attenuator Calculator (in Excel), which calculates the number of resistors an their values.
You can use use the Calculator to design attenuators with an input power of 2.5 watt for use with your FT-817.
Play with the values, see what happens, with each new choice.
Bert is it really that easy? . . .
Read more about attenuators
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