User's Manual

2.3 Interference Prevention

CAUTION: Interference may occur if the audio system is not properly installed.

The following types of interference could occur if precautions are not taken during

installation. Read this section carefully before proceeding.

2.3.1 Radio Frequency (RF) Interference

Finding the cause of RF interference is difficult and time-consuming. The following

precautions will help you avoid the most common RF interference problems.

 Find the best base station and antenna locations before mounting them.

 Solder all joints (including crimp joints) at the speaker location. This is very

important in damp climates

 Be certain all connections are tight.

 Avoid leaving unshielded wire anywhere in the audio system.

 Ground the shield of the outgoing speaker cable. In severe cases of interference,

grounding the shield at the speaker may help.

AM and FM interference may cause similar problems but require different corrective

action. AM interference may increase or decrease at certain times of day, since AM

transmitter power must be reduced in some areas between 5 and 7 PM.

Note the following symptoms carefully to determine the possible cause of

interference. Call HME at 1-800-848-4468 if you need help.

AM Interference:

Static or hum may be heard in the headset when the system is active. The AM

interference can enter the system through the cables connecting the outside

speaker/microphone to the base station. To block the AM signal, first find out if

there is an AM station in the area, and find out its operating frequency and

transmitter output power. You can then modify the equipment with a network of

inductors and capacitors that will trap the AM signal where it enters the system.

Static, hum and/or voice may be heard in the headset when the system is active or

when transmitting in either channel A or B. The interference can enter the system

at three different locations: the outside speaker cables, the COMMUNICATOR

receiver and the base station transmitter. The AM station frequency may completely

suppress or overpower the audio system’s transmitter signal, depending on the

operating frequency, transmitter tower location and output power of the AM radio

station. You may need to move the base station.

FM Interference:

FM interference may cause cracks, pops and other noises to be heard in the headset

when the Communicator is transmitting on either channel A or B, or when the

system is active.