EFJohnson 7780 Transmit Frequency and Power, Transmit Power Adjustment Screen, Modulation Balance

ALIGNMENT PROCEDURE AND PERFORMANCE TESTS

7.5 VDC

Power Supply

R73

(Freq Adj)

R13

(Sq Lvl Adj)

(–) Neg

(+) Pos

Figure 6-3 Connecting DC Power

6.1.6 REMOVING TRANSCEIVER COVER

NOTE: The transceiver cover needs to be removed only if the frequency and squelch adjustments described in Sections 6.2.1 and 6.6 need to be reset.

The frequency and squelch noise level adjust- ments are made by manually resetting controls on the RF board. To access these controls, proceed as follows:

1.Remove the battery, belt clip, and back cover as described in Section 1.11.

2.An external power supply must then be connected to the transceiver as shown in Figure 6-3.

6.2 TRANSMIT FREQUENCY AND POWER

6.2.1 FREQUENCY ADJUSTMENT

Frequency adjustment should be performed with the ambient temperature near the TCXO calibration reference of 77° F (25° C). This ensures that the frequency will be within tolerance at the temperature extremes. Proceed as follows:

NOTE: The transmitter immediately keys when the following function is selected. To turn the transmitter on and off, click the “Toggle” button (see screen which follows).

1.Connect a wattmeter and dummy load to the antenna jack as shown in Figure 6-1.

2.Click the “Complete Tune” button to automatically go from one adjustment to the next or click the “Tune” button in the “Tx Power” box to perform only this adjustment.

3.Monitor the transmit frequency with a communica- tions monitor set to the frequency displayed on the screen.

4.At room temperature, this frequency should be within ± 400 Hz. If readjustment is required, remove the cover as described in Section 6.1.6 and adjust R73 (see Figure 6-3) for the correct frequency. This also adjusts the receive frequency.

Transmit Power Adjustment Screen

6.2.2 POWER OUTPUT ADJUSTMENT

Set the high and low power output by clicking the arrows or moving the button in the scroll bar. The rela- tive power level is indicated by the number in the box. Set the high and low power levels as follows:

High Power Level = 3.0 watts

Low Power Level = 1.0 watt

6.3 MODULATION BALANCE

1.If manually selecting each test, click the “Tune” button in the “Modulation Balance” box. Otherwise, this function is selected automatically when the “Complete Tune” button is clicked.

2.View the transmit modulation waveform on the CRT of a communication monitor. If applicable, set the monitor for de-emphasis off, high-pass filter off, low-pass filter 3 kHz, and FM peak detection active.

November 1999
Part No. 001-7780-500	6-4