0 - 36 dB Power Attenuator for 5 watts

A simple way to reduce the power of your QRP transceiver, without modifying the set, is the use of attenuators.  This 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.

A 3 dB attenuator devides the power by 2
A 10 db attenuator reduces the power to 1/10th
and a 20 dB attenuator to 1/100th.

This 0 - 36 dB step attenuator enables you to adjust the power in steps of 3 dB and 4 dB.
A step of 3 dB is the optimal step to increase the power for the use in QSO's.
(1 dB is too small and 10 dB is too large)

Click, to read, how to use the
lowest possible power in QSO's.

The PA1B Power Attenuators are all built with good available resistor from the E12-series, with a modest power. By placing two or more resistors in parallel, to form the compound resistors R1 to R9, the power is distributed over the resistors. This allows the compound resistor, to handle much more power, than an individual resistor. The simple layout of the circuit eliminates the need of a PCB. The attenuators are very accurate.

The three schematics below, show the PA1B 36 dB Attenuator, for an input power of 0.7 W to 5 W.
The maximum input power depends on the number of resistors and the power of the resistors.

  • The higher the power of the resistors, the higher the maximum input power of the attenuators
  • The more resistors, the higher the maximum input power

  • Please notice, that the Attenuators are asymmetrical. Input and output should not be reversed.
    This can damage the attenuator.

    0 - 36 dB Attenuator for 0.7 W, 1.5 W or 3 W 

         Scroll down for higher power

    0 - 36 dB Attenuator for 1.1 W, 2.2 W or 4.4 W

    0 - 36 dB Attenuator for 1.3 W, 2.7 W or 5.4 W

         When the S-meter goes up, 
         my power goes down.  

    Attenuator set to 16 dB

    5 opmerkingen:

    1. Dear Mr. Bert

      I think what you're doing, the way you work is incredibly interesting and original. Furthermore, the scientific value, in terms of the distribution of RF waves is invaluable. My colleague LZ2UV (LZ6C) showed me that you made the connection by 1.8 mW. As a telecommunications engineer I was completely amazed. I did not believe that is possible connection with such power of more than 100 m

      Please accept my most cordial greetings! 73

      Boby, LZ4FQ

      1. Hello Boby, thank you for your fine comment. What I do feels very special.
        It's great fun to make contest QSO's in CW with very low power. I remember the 36 mW and 1.8 mW QSO with LZ6C. It's very nice to meet these fine op's with Excellent Ears
        It's all a matter of propagation. I made QSO's with 50 mW with German stations that used 1 kW themself. hi
        Please visit my the "PA1B QRPp page" to read more interesting stories.
        Thanks again for your fine comment, I enjoyed it very much.
        73, Bert

    2. Hello Bert,

      Thank you for the great article. I have successfully build a 36dB attenuator for 20W (max portable power for a FT-897) and am very pleased with the new possibilities on hamradio with it. A link to the building report (not finished yet) can be found on : http://www.bolkesteijn.nl/blog/index.php?page=36db-attentuator

      73 de Lex

      1. Hallo Lex, WOW, What beautifully built Attenuator.
        Thank you for using the Power Attenuator Calculator, to design your 36 dB attenuator for 20 watt.
        I love your video on the test of the Attenuator, with an input power of 5 watts.
        Your video shows, that both the 36 dB attenuator and your OZ2CPU 1W QRP uW meter are very accurate.
        Thank you for the link to your website. Good luck in QRPpp. hi 73, Bert

    3. tanks for coments abt my resistors Bert, i will look at it soon. i had to rebuid my entire homepage because the old hotel couldnt remove some bad things in the program. Now i finaly found a new hotel with Wordpress for a reasonable prize closer than USA. The new adress is www.sm5mek.se Only www is new on adress. Realy like your blogpage, clean and easy to read. Best 72 de SM5MEK