Specifications

2–12

FM500 User's Manual

2.10 Audio Monitor Connections

Processed, de-emphasized samples of the left and right audio inputs to the stereo

generator are available at the Monitor jacks on the rear panel. The signals are

suitable for feeding a studio monitor and for doing audio testing. De-emphasis is

normally set for 75 µsec; set to 50 µsec by moving jumpers, JP203 and JP204, on

the Stereo Generator board.

2.11 Pre-emphasis Selection

Select the pre-emphasis curve (75 µsec, 50 µsec, 25 µsec, or Flat) by jumpering the

appropriate pins of header JP1 on the audio processor board. If you change the

pre-emphasis, change the de-emphasis jumpers JP203 and JP204 on the Stereo

Generator board to match.

2.12 Processor Bypass Option

You may bypass the audio processor in order to feed the left and right (pre-

emphasized) audio directly to the stereo generator. The Normal-Bypass slide

switch is near the left-rear corner of the motherboard. If the audio source is

already processed and you do not desire further processing, use the Normal mode

but turn the Processing control (on the front panel) to “0.” (See also section 3.5.)

In the BYPASS position, the pre-emphasis circuits and the filters that protect the

pilot and stereo subcarrier are bypassed. As a result, the occupied bandwidth

specifications of the transmitter could be compromised. The 15–Hz high-pass

filters are also bypassed which may mean that modulation with frequencies

below 10 Hz could cause the frequency synthesizer to unlock.

CAUTION

Illustration 2–13 Composite In and Audio Monitor Connections

SCA IN

COMPOSITE IN

MONITOR

REMOTE I/O

RIGHT

LEFT/MONO

Audio Monitor

(RCA) Jacks

Composite Input

(BNC) Connector