Motorola SABER RVN4002K User Manual

Page 38

VCO and Reference Modulation Alignment

When adjusting deviation, two separate adjustments are required - one for VCO modulation
and the other for REFERENCE modulation. When aligning VCO and Reference Modulation,
you can measure the deviation during the alignment process or in "real time." You do not
have to reprogram the radio to measure the change. However, you will have to reprogram
the radio to make these changes permanent. Do NOT turn off the radio while aligning this
parameter. The procedure given below will go through both of these adjustments.

(a) Follow the Setup Procedure in Section VI-A, Fig. 8.

(b) Connect the RF BNC connector to a 50 ohm load and to a service monitor so that you

can measure deviation.

key.

(d) Using the UP arrow key, set the VCO Modulation value to $1F.

(e) Select the REFERENCE Modulation function on the ALIGN CHANNEL menu by using

the ENTER key.

(f) Using the UP arrow key, set the REFERENCE Modulation value to $0F.

(g) Now select the VCO Modulation function on the ALIGN CHANNEL menu.

(h) Apply a 1 kHz, 25 mVrms tone to the external microphone port on the test set. Measure

this level at the AC/DC metering jacks on the Portable Test Set. Measure deviation by
keying up the radio.

(i) De-key the radio and adjust the VCO modulation value (decrease the value if the

measured deviation is higher than the required value) by using the DOWN key to
decrement value. The valid range for this parameter is from $00 to $1F with a default
value of $1C.

(j) Re-key the radio and measure the deviation. Repeat the procedure (this step and the

step above this) until the required deviation is reached.

(k) Apply a 0.355 Vrms, 1 kHz tone to the auxiliary transmit port on the radio (the female

BNC connector). The signal level should be measured with the audio generator
connected to the radio. To do this you will have to use a T-connector so that you can
simultaneously apply the signal to the radio as well as applying it to the AC meter.

(l) Select the REFERENCE Modulation function on the ALIGN CHANNEL menu by using

the ENTER key. By selecting this function, the radio service software enables the
auxiliary port of the radio after being keyed.

NOTE

Reference modulation cannot be aligned on channels that have MDC signalling
enabled. On completion of the MDC signalling, the radio disables the auxiliary port.

(m) Key the radio, and measure this deviation and note it as DEV 1. De-key the radio.

(n) Remove the 1 kHz tone and apply a 0.355Vrms, 20 Hz tone to the auxiliary port.

(o) Key the radio, and measure this deviation and note it as DEV 2. De-key the radio.

Servicing the Radio