T/Pi Pads                  Calculate the minimum loss and resistance values for T                  and Pi pads.                  Units:  ohms,dB                  Choose T or Pi (T or P) [<Enter>=Quit] ? _

What are the resistor values needed to make a 3 dB T-Pad to use in a 50 ohm system?

                Min. Loss = 0.000 dB

                Desired Loss (dB): ? _

Input "3" as the desired pad loss and press <Enter>.

Note: Always enter the desired pad loss as a positive number.

Here are the resistor calculations for the 3 dB T-Pad:

                R1 = 8.550 ohms
                R2 = 8.550 ohms
                R3 = 141.926 ohms 

Note 1: If the above pad was fabricated for use at low frequencies, using standard 5% resistors, the closest values would be: 10, 10, and 150 ohms. This would introduce a small error. Theoretically, as can be determined using our Sceptre program, the loss would be 3.17 dB and would introduce a VSWR of 1.057.

Note 2:  If Z1>Z2, i.e., there is a mismatch in resistance at each end, then there is a certain minimum attenuation that can be achieved. Try a Pi-Pad with Z1=75 and Z2=50 (Z1 must be > Z2). Note that the minimum loss is 5.719 dB, so, practically speaking, a 6 dB pad is the nominal minimum sized pad because of the additional requirement to "match" between 75 and 50 ohms.