[ARC5] [Milsurplus] Smart People: Attenuators

[mac]

Agree with John, 10W for the input shunt, 1/2 watt units OK for the  
other two resistors but I (personally) would use 1 or 2W units.  All  
resistors must be non-inductive, of course.

Dennis D. W7QHO
Glendale, CA

****************
On Mar 2, 2011, at 7:51 PM, David Stinson wrote:

> Need the help of you smart people again.
> I built a "utility" linear HF amplifier to help put QRP transmitters
> on the air.  Works great with the correct drive,
> which is 10 milliwatts.
> I need to attenuate drive levels from a couple of hundred milliwatts
> up to about 6-7 watts, so need a variety of pi-type attenuators.
> The resistance values are no problem,
> because someone wrote a Java app:
>
> http://chemandy.com/calculators/matching-pi-attenuator-calculator.htm
>
> My question:
> What's the formula for the Wattage rating of each resistor?
> For instance:  If I have a 4-watt drive signal and need to get it down
> to 10 milliwatts (assuming 50 Ohms in and out),
> I need to attenuate 36 dB.
> That's shunt in 52 Ohms, series 1580 Ohms, shunt out 52 Ohms.
>
> How to calculate the appropriate wattage of the three resistors?
> Common sense says the shunt input should be big enough to
> sink the entire carrier power, while the series and shunt out
> could be smaller.  What's "right?"
>
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