Monday, December 13, 2010

Lesson 17: General Class Exam Course G4C

Here is lesson 17!  This lesson covers the G4C section of questions from the exam pool dealing with interference and grounding.

There are a few items that you may want to focus on in this section.  There are a couple of questions that deal with filters used to prevent RF interference (RFI).  Sometimes the speaker wires of a stereo can pick up signals from your transmitter and interfere with the stereo speakers.  A way to limit the interference to the speakers is to install a Bypass Capacitor along the speaker wires.  The other type of interference common between hams and consumer electronics is interference with a nearby telephone.  For this question on the exam, the solution you are looking for is to install an RFI Filter at the affected telephone.

A common theme in the questions dealing with station grounding is to keep the ground wire from your station to the ground as short as possible.  Long ground wires may resonate like an antenna at certain frequencies.  This prevents the ground wire from doing its job and sending unwanted RF energy to the ground.  If this is happening it can cause RF hot spots to build on your station equipment possibly giving you an RF burn if you touch the wrong thing.  Keep ground wires short!

Please leave any comments, suggestions, and questions you may have!


1 comment:

  1. As I'm sure you're aware, the current test good until July has the answer to G4C05 being: "The ground wire has high impedance on that frequency." So, which is correct for real? That, or, "The ground wire is resonant"?