Instruction manual

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the AUDIO PROCESSING switch in the IN position

unless outboard provision is made for pre-emphasis

and limiting. Without external pre-limiting, program

material will be driven hard into the clipping circuits

and result in egregious distortion..

PILOT

The PILOT switch lets the user manually turn off the

19kHz stereo pilot for certain tests. Since the 19kHz

pilot is necessary for proper system operation, the

switch should always be left ON. The green LED

indicates normal operation, the red LED lights

whenever the pilot has been turned off.

MODE

Under some circumstances it may be advisable to

broadcast monaurally. For example, should the

station suddenly suffer an emergency power loss,

temporarily reverting to mono transmission would

help regain some of the lost coverage until full power is

restored.

When switched to MONO, the MODE switch removes

both the stereo subcarrier and the 19kHz pilot. The

transmitted signal will consist of L+R, the algebraic

sum of the left and right program channels. The

MODE switch does not remove an RDS or an SCA

subcarrier.

POWER

‘Nuf said.

NORMAL SETUP PROCEDURE

This setup procedure presupposes a normal installation with the

DAVID-II PROGRAM LINE INPUT fed directly from the output of the

audio console and a direct connection of the COMPOSITE OUTPUT to the

wideband input of an exciter/transmitter. Variations from these

conditions, such as an intermediate STL (or other link) in either the

input or the output path of the DAVID-II, may call for considerations

not addressed here.

At this point the DAVID-II should be installed in the program chain

with power applied, and have all front-panel function switches ON.

AVERAGE COMPRESSION should be set at 6dB and COMPOSITE

PROCESSING turned OUT.

Input Gain

Calibration

Left (L) and right (R) INPUT GAIN controls are set individually to

center the AGC operating range at the nominal “Zero-VU” program

line input level. If the following procedure shows control range to be

outside adjustment limits, recheck circuit board jumpering for Line

Input Range Selection as described on Page 8.