The following information ONLY applies to Trunked Maxtrac's. DO NOT try it on conventional radios, unless you want to replace the logic board.
In normal field operation, the microcomputer in the radio controls RF channel selection, transmitter key-up, and receiver muting functions. However, when the unit is on the bench and is out of its normal operating environment, the microcomputer does not key the PA or unmute the receiver, and this prevents use of normal test procedures. To solve this problem, a special test routine has been incorporated into the radio.
Initial Setup
To enter the TEST mode, short across VR806 on the Logic Board prior to turning the radio on. This grounds the Serial Data Input (SERIAL BUS+). To exit the TEST mode, turn the radio off, remove the short, then turn the radio back on.
NOTE: You can also create an adapter cable that shorts the SCI+ pin to ground through the mic jack (pins 7 and 4) and still lets you plug a microphone in. This would relieve you from having to open the radio to apply the short and still be able to use the microphone jack for further testing (below).
There are seven TEST frequencies: three fixed TEST mode frequencies (see table below), and four control channel frequencies of the system selected when the TEST mode was entered.
| TESE MODE CHANNEL | RECEIVE FREQUENCY | TRANSMIT FREQUENCY |
| 1 | 851.0125 MHz | 806.0125 MHz |
| 2 | 869.9875 MHz | 824.9875 MHz |
| 3 | 860.5125 MHz | 815.5125 MHz |
Operation of the radio in TEST mode is described in the following paragraphs and is the same whether using the customer codeplug frequencies or the internal plug test frequencies.
Channel Selection and Receive Mode
Short across VR806 (as described above). Apply power to the radio. A single 450 Hz beep in the speaker indicates operation on test mode Channel 1 (CH1), after which the receiver unmutes.
Step the radio to the next channel by tapping the microphone PTT button (push the PTT and release it within 200 ms). Two beeps in the speaker indicate CH2, after which the receiver unmutes. Repeat this procedure to step the receiver from CH1 through CH7 with the number of beeps indicating the chosen test channel. CH1 through CH3 are fixed test mode frequencies.
NOTE: The test mode cycles, which means that the radio reverts back to the first frequency (CH1) after the last possible test mode frequency.
Transmitter Alignment Modes of Operation
Three transmit modes are used for variuos transmitter checks and adjustments.
Transmit Mode 1: Silent Carrier
On a given test channel, when the microphone PTT button is pressed once and held, the microcomputer keys the PA without data modulation, and MIC audio is enabled. In this mode, the transmitter frequency, hum and noise, and voice deviation can be checked and adjusted.
When the PTT button is released, the PA is de-keyed and the receiver unmutes.
Transmit Mode 2: Sub-audiable Connect Tone Plus Voice (Low-Speed Mode)
If the microphone PTT button is pressed and held a second time, the power amplifier is keyed with low-speed sub-audiable tone modulation, and a pulsed 150 Hz tone is heard at the speaker. This 150 Hz tone is the BUSY tone. This procedure is used to adjust the maximum voice plus sub-audiable tone deviation. Deviation levels are shown below.
When the PTT button is released, the PA is de-keyed and the receiver unmutes.
NOTE:The low-speed sub-audiable tone may be 76.60 Hz, 83.72 Hz, 90.00 Hz, 97.30 Hz, 105.88 Hz, 116.13 Hz, 128.57 Hz, or 138.46 Hz. The specific tone is coded in the codeplug, and is a specific tone for a specific system.
Transmit Mode 3: High-Speed Acknowledge Tone (High-Speed Mode)
If the microphone PTT button is pressed and held for a third time, the PA is keyed with 1800 Hz tone modulation. The MIC audio is disabled and a 900 Hz alert tone is heard at the speaker. This tone is known as talk permit. This step is used to check high-speed data deviation. The deviation levels should be 2.4 kHz to 3.1 kHz.
When the PTT button is released, the PA is de-keyed and the receiver remains unmuted.
NOTE: Repeated pressing and releasing the PTT button cycles the radio through the three modes as described above.
NOTE: If any of the above tests indicate that adjustment of the transmitter deviation is necessary, refer to the Maxtrac Radio Service Software package for procedures.
