Operating instructions

In response to the +, or – keys (or m, p, M, or P), the firmware adjusts the deviation

digital POT. The user should do this until the deviation is about 200Hz below the value

shown.

The firmware will now repeat this for the following standard deviations, 5.0kHz,

4.5kHz, 4.0kHz, 3.5kHz, 3.0kHz, 2.5kHz, 2.0kHz, and 1.5kHz.

6.2.4 The “Tone Deviation” Calibration Procedure

T50> cal tone

This procedure should not normally be invoked as part of any field maintenance.

Note that if the deviations are calibrated, then this procedure will be automatically

invoked.

This procedure is similar to the maximum deviation procedure (See 6.5). The Line 1

and Line 2 audio paths are turned off for this procedure, as is the Direct Audio (TONE)

input. The only signal sent to the modulator is a tone of 107.2Hz.

The program starts off, with the following message:

This procedure sets the maximum tone deviations for a

Max Deviation of 5kHz. Note that the actual maximum

tone deviations automatically scale with the Max Deviation.

eg a 500Hz tone deviation would be a 250Hz tone deviation

when a 2.5kHz Max Deviation was chosen.

Disconnect the RF connection to the PA,

and connect a deviation meter to the exciter's BNC output.

The audio is being switched off, and 107.2Hz tone generated

Thence a procedure that is almost identical to that used for setting maximum deviations

is used to set these tone deviations. There is one significant difference, though, and that

is, as well as using + (or p, or P), and – (or m, or M) keys to step the deviation up or

down, one can also use the < key, or the > key. These last two keys will step down, or

up, the level of signal transmitted by U500, whereas the other keys will modify the

setting of the digital POT U503 (see 5.5).

This procedure is used to set tone deviations of 750Hz, 700Hz, 650Hz, 600Hz, 550Hz,

500Hz, etc down to 150Hz.

6.2.5 The “Line” Calibration Procedure

T50> cal line

This procedure should not be used as part of any usual field maintenance, unless any

component has been replaced that might affect the gain of any of the audio inputs.

Note that if the deviations are calibrated, then this procedure will be automatically

invoked.

The program begins:

Calibrating Line 1 and Line 2 audio levels

Attach an audio signal generator to Line 1

Set the output to be a sine wave, 388mV rms and 1kHz

Disconnect the RF connection to the PA

and connect a deviation meter to the exciter's BNC output.

Enter + or - to increase or decrease the deviation,

and <RET> when the deviation is 3kHz.