Going further

What we now have is a calibrated 50 MHz RF source that we will use to test our next two projects. As I mentioned before, the output is 0 dBm. This is just the value I chose. You can set it to any value you like using the attenuator calculator web page. In all projects from now on, I will assume that you are using a 50 MHz 0 dBm source.

You can achieve different output levels by using either a fixed or variable attenuator. The following image shows an example of a fixed attenuator:

SMA attenuator (copyright Mini-Circuits)

I used an SMA connector on my prototype because of its small size and ease of mounting to the PCB. Theses connectors have a much higher frequency range than we will be using on these boards, so you can use a BNC connector if you like. The following image is of a BNC-type attenuator:

BNC attenuator (copyright Mini-Circuits)

A manual variable attenuator is shown in the following image. If you are lucky enough to either have or borrow one of these, your life will...