# Two-port network models (V in & V out)

1. Oct 12, 2013

### agata78

1. The problem statement, all variables and given/known data

Construct and test the ∏ section symmetrical attenuator. Measure and record the Input & Output Voltages of the attenuator and determine the attenuation in dB.

2. Relevant equations

Vout = Vin * [ R2 / (R1 + R2) ]

Decibel Attenuation (dB) = 20LOG10(Vout / vin)

3. The attempt at a solution

I have included an attachment for this question. The main area where I am confused at the moment is the number for Vin. Can someone please guide me to how to work out Vin?

#### Attached Files:

• ###### P2.2(a).png
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2. Oct 12, 2013

### The Electrician

Looks like a lab experiment to me. Your instructions are to "construct and test".

Vin is the voltage you get from a signal generator. You connect the signal generator to the input of your attenuator and then measure Vin. You don't "work out" Vin; you measure it, just as you measure Vout.

3. Oct 12, 2013

### agata78

Then do I simply make up an Input Voltage to carry out the further calculations?

4. Oct 12, 2013

### The Electrician

Your problem statement says " Measure and record the Input & Output Voltages of the attenuator and determine the attenuation in dB."

It doesn't say anything about any calculations.

Choose a reasonable signal level for your input, something like 1 volt AC at perhaps 1 kHz.

If you measure the voltage out of the generator without the attenuator connected, be aware that the input voltage to the attenuator when connected will be less due to the loading effect of the generator.

You may later be required to compare your measured results with calculated results, but the problem you have stated in post #1 doesn't say anything about that. It just says to make measurements.

5. Oct 15, 2013

### agata78

The next part of the question is:

Test your symmetrical attenuator (practical) against computer models.

Can please someone quide me in the right direction to answer this question as I am struggling to work it out?

6. Oct 15, 2013

### The Electrician

Testing your attenuator against computer models means to note whether your measurements are reasonably close to what you calculated.

The point of all this is to show whether or not your computer models give the same results as reality (measured results). If this is true, then you can design attenuators using models and be confident that the resulting design will work.