noise-less switchable attenuator

Now this sounds a bit daft, but switchable attenuator are usually made from resistors, thus the carbon noise from the resistor would raise the noise floor up and thus reduce the noise floor of the radio set. The only other resistor that would perhaps not produce carbon noise could metal film resistors for signal attenuator pads.

However I was wondering about the use of a step down signal transformer, a 10:1 ratio would step down the signal voltage by ten times, or 20dBV attenuation.

equation dBV = 20log₁₀ ( voltage ratio )

The circuit below illustrates an signal transformer type in line switchable attenuator.

Remembering that the square root of the impedance ratio is equal to the turns ratio, a 10:1 turns ratio to reduce the signal voltage to a factor of ten times, would equate the secondary impedance to half an ohm, the "T-section" low-pass filter circuit thus impedance transforming from half an ohm to 50ohm impedance. In the above circuit, the attenuators are not made from resistor pads, so hopefully the carbon noise that would be present within resistors, and as resistors are not used within this application, only the radio signal voltage would be reduced, and thus not raising the noise floor of the radio.