Bode expression syntax error check

[Terry2000]

.ac dec 10 10 10Meg
.plot vdb(2) vp(2)*180/3.14159
I want to produce a freq response and phase angle of a low pass filter. Using the expressions above returns ‘syntax error’ for the second line.

If someone can see my error pls suggest a correction.

Thanks

[ivan1]

You need to use mag(V(2)) → magnitude, ph(V(2)) → phase

.plot mag(V(2)) ph(V(2))

Best regards

[Terry2000]

Thank you ivan1. I need to read up some more on this.
The solution gave ‘syntax error’ again.

[ivan1]

Here you need to try like this. Phase is degrees and looks like it has wrong sign.

Best regards

[KSKelvin]

In polar representation plots of complex numbers, the left axis always displays magnitude only, which always +ve. If you display the right axis, you will observe a constant 180 degrees for ph(V(2)).

Complex number calculations always yield complex numbers as results. Polar representation plots show Magnitude/Phase, while Cartesian representation plots show Real/Imaginary components.

[Terry2000]

Thank you. I had a typo that you helped me see.
Worked for my first Run then fails for subsequent Runs, so wierd!

My update: Works when I add a Label “2” as per your diagram.

Second question, if I may: I want to check my audio amplifer circuit with a Bode plot. Can you recommend an information source from where I can learn where to place the Label ?

Cheers

[ivan1]

When you need to draw bode plot you dont need to use mag and pha commands. You need only to click on the node of interest. Naming nodes is used only so you can know what trace is what.
Here out is labeled and when you plot your trace has same name:

Best regards