Motorola HT 1000 service manual Front-End Pre-Selector VHF/UHF only, Rated Audio

Front-End

Pre-Selector (VHF/UHF only)

NOTE: This procedure is only required for tuning the front-end filter varactors in the VHF and UHF models. The 800 and 900 MHz models utilize a stripline pre-selector.

1.Set the Test Box (RTX4005B) meter selection switch to the “VOL” position, and connect a dc voltmeter capable of 1mV resolution on a 2V scale to the Test Box AC/DC meter port to monitor the Received Signal Strength Indicator (RSSI).

2.From the SERVICE menu, press F3 to select RECEIVER alignment.

3.Press F2 to select the FRONT END FILTER softpot. The screen will indicate the receive frequencies at which the filter is to be tuned.

4.Set the RF test generator to the first receive frequency +150 Hz. Set the RF level at the radio standard antenna port to 4.0 µVolts with no modulation.

5.Adjust the UP/DOWN arrow keys to obtain a peak voltage on the dc voltmeter.

6.Press F8 to program the softpot value.

7.Repeat steps 4-6 for the remaining test frequencies.

8.Press F10 and F2 to return to the RECEIVER menu.

Rated Audio

1.Set test box (RTX-4005B) meter selection switch to the “AUDIO PA” position and connect an ac voltmeter to the test box ac/dc meter port.

2.Press F3 to select the RATED AUDIO softpot. The screen will indicate the receive test frequency to be used.

3.Set the RF test generator to the receive test frequency, and set the RF level at the radio standard antenna port to 1 mV modulated with standard test modulation (see Table 14).

Table 14 Standard Test Modulation (1 kHz Tone)

Band	Deviation
VHF/UHF/800 MHz	3.0 kHz
900 MHz	1.5 kHz

4.Adjust the UP/DOWN arrow keys to obtain rated audio (as close as possible to 3.74 Vrms) into a speaker (28 ohms) or equivalent resistive load.

5.Press F8 to program the softpot value.

6.For HearClear-equipped radios, go to step 7; otherwise press F10 to return to the RECEIVER menu.

7.Now set the RF test generator to the receive test frequency, and set the RF level at the radio standard antenna port to 1 mV modulated with a 1kHz tone, 1.2kHz deviation.

20