15 dB Step Attenuator Design and Build

15 dB Step Attenuator Design and Build

Using PA1B's Power Attenuator Calculator, I calculated the resistor values for 

3 , 2 and 1 dB attenuators. 

I did not have DPDT Switches therefore I used 2 SPST for each attenuator.

Schematic will be uploaded soon.

Here is the layout:

Steps Of Build:

Attenuator installed in my QRP Shack.

The Attenuator will enable me to reduce the output power of my YouKits HB1B CW Transceiver in order to feed my HF Packer Amp.

Why? Because my Alexloop antenna can only handle 10 Watts Maximum on CW transmissions.

The main reason I wanted to build the attenuator is for the Attenuator and my HF Packer Amps output is approximately 35 Watts with an input of 5 Watts (+ OR - 1  WATT).

The Step Attenuator Worked GREAT!  I was able to attenuate my CW signal feeding the amp in order to get my desired 10 Watt output!

The Following Table Shows Input VS Output  Tests with Different Attenuation

Attenuation (dB)	INPUT (Watts)	OUTPUT (Watts)
1	3.9	35.4
2	3.2	28.8
3	2.5	22.5
4	2	17.5
5	1.7	13.3
6	1.3	9.9
7	1	6.9
8	0.8	5.3
9	0.66	3.6
10	0.53	2.7
11	0.42	1.9
12	0.35	1.3
13	0.3	1.1
14	0.24	0.8
15	0.18	0.6

The Following Calculations Are Based On Actual  Input VS Output  Measurements  with Different Attenuation.

You will notice that the values are very close. I am satisfied with the results!

Input + 4.74 Watts

1 dB Attenuation Test:
                                                   
dB =10*LOG(4.74/3.92) = .825  

2 dB Attenuation Test:  

dB=10*LOG(4.74/3.2) = 1.7

3 dB Attenuation Test:

dB=10*LOG(4.74/2.52) = 2.7

4 dB Attenuation Test:

dB=10*LOG(4.74/2.04) = 3.66

5 dB Attenuation Test:

dB=10*LOG(4.74/1.65) = 4.6

6 dB Attenuation Test:

dB=10*LOG(4.74/1.33) = 5.5

7 dB Attenuation Test:

dB=10*LOG(4.74/1.02) = 6.7

8 dB Attenuation Test:

dB=10*LOG(4.74/0.824) = 7.6

9 dB Attenuation Test:

dB=10*LOG(4.74/0.669) = 8.5

10 dB Attenuation Test:

dB=10*LOG(4.74/0.53) = 9.5

11 dB Attenuation Test:

dB=10*LOG(4.74/0.423) = 10.5

12 dB Attenuation Test:

dB=10*LOG(4.74/0.348) = 11.3

13 dB Attenuation Test:

dB=10*LOG(4.74/0.298) = 12

14 dB Attenuation Test:

dB=10*LOG(4.74/0.246) = 12.8

15 dB Attenuation Test:

dB=10*LOG(4.74/0.185) = 14