36dB Attenuator for 20 W by PH2LB

This beautiful attenuator is designed and built by Lex PH2LB.

0...36 dB attenuator built by PH2LB  -  Click to enlarge the pictures

Power
The attenuator can handle a maximum power of 20 watt.
At first I did not realized why Lex designed the attenuator for 20 W. Like many HAMs I thought, that 20 W is QRO. But please notice that 20 W is the Maximum power.  The chosen maximum power of 20 watts for the attenuator is an excellent choice. The attenuator can easily handle a power of 5 watts, without getting hot. The nominal power of the attenuator is 5 Watt.

This was an eye-opener for me. hi.

0...36 dB attenuator by PH2LB
with 2 W resistors 

Derating
A resistor that  dissipates its maximum power will get very hot.
So it is good practice to choose the maximum power 4 times higher then the continuous power.
Lex choose for  a maximum power of 20 watts, to reduce a power of 5 watts.
The resistors have a maximum power of 2 watts. With a power of 1/4 of the maximum power, the resistors will dissipate about 500 mW each and they will get warm, but they will not get hot.

The 20 dB section

Visit the article on the 36 dB attenuator on the web site of Lex PH2LB.

PA1B Power Attenuator Calculator
Lex used the PA1B Power Attenuator Calculator to design his 36 dB attenuator for 20 watts.
This unique spreadsheet in Excel calculates the number of resistors and the values of the resistors from the E12-series for an attenuator section.

In the picture below I show the input values for the section of 20 dB, for a maximum power of 20 watts, that is built with resistors of 2 watts.

PA1B Power Attenuator Calculator - Input values for the 20 dB section

Just download the PA1B Power Attenuator Calculator and play with the values. The calculator has no restriction on the power.

Meeting Lex PH2LB

Lex - PH2LB

Last week I visited the HAM convention 2016 - Dag voor de Radioamateur 2016 in Apeldoorn.
I was very pleased to meet Lex PH2LH.
Lex has designed a 0 - 36 dB attenuator for 20 watts, using the
PA1B Power attenuator calculator.

When I approached the stall of Lex, I immediately recognized the 0 - 36 dB Attenuator that Lex has designed and build.
Further Lex showed the beautiful build OZ2CPU digital RF mW / dBm / mV meter.

OZ2CPU digital RF mW / dBm / mV meter
   and the  0 - 36 dB attenuator

PA1B 0 - 36 dB Attenuator for QSO's

Last week, the info  on the interesting Attenuator page  of my web site was updated.
I added new info on the PA1B 0 - 36 dB Attenuator, specially designed for QSO's (Click)
I also placed new info on the PA1B 0 - 36 dB Attenuator, under the Tab's on the top of this Blog.

A simple way to reduce the power of your QRP transceiver, without modifying the set, is the use of attenuators.  This accurate PA1B  0 - 36 dB attenuator, is an excellent attenuator, to use in QSO's with very low power. This attenuator enables you, in contest QSO's, to go to the next setting instandly, when your call is not heard.
The combination   20 dB - 10 dB - 3 dB - 3 dB  is very quick to adjust in contest QSO's.
The choice of the values, makes it very easy to calculate the power at the output instantly.
This accurate Power Attenuator is designed for the use in QSO's.
With only 4 switches it is surprisingly fast and easy to operate.

Power Attenuator Calculator
I use the excellent Power Attenuator Calculator (Click), for the
design of the Power Attenuators.
With the Power Attenuator Calculator, you can design an attenuator for any input power.

Read more about attenuators on the attenuator Page.

On  my web site: Home - PA1B QRPp page