Specifications

RV-M7 Technical Manual

2. The modem will now put out CW on the center of the channel.

3. Read the frequency offset with the ATR8 command.

4. Adjust the frequency to the center of the channel with the ATR8 command. You can use

the “U” key and the “D” key to change the settings up and down one value in real time.

12.4 TX Deviation

1. Switch to channel 1.

2. Key the transmitter into a 50 ohm load using the ATTD 3 command. The unit will now

transmit, and send a digital 0 continuously. This should be +2.0kHz in frequency for

narrow-band radios (12.5kHz spaced channels) and +4.0kHz for wide-band (25kHz

channels).

3. Adjust the deviation register setting so that the frequency deviation is correct. The

deviation is set with a digital adjustment. Use the ATR0 command to read or set the

deviation level.

12.5 TX Modulation Balance

(Note: This step is not performed on radios with Radio Type 5)

1. Set-up a service monitor to monitor the FM deviation of the transmitted signal on an

oscilloscope. The frequency response of the demodulated FM signal must be greater

than 10Hz to 5kHz without any de-emphasis.

2. Transmit random data on the center of the band, using the ATDT 1 command. This

command will cause the M7 to automatically key up, and send random data for one

minute.

3. Verify the DC center of the demodulated data is stable. The random data should be

randomly timed 1s and 0s, and have little to no AC component on them. See pictures

below for details.

4. If necessary, change the ATR9 setting so that the long data bit have the same amplitude

and DC value as the shorter ones.

5. On the low end of the band, adjust ATRL so that the modulation is proper.

6. On the high end of the bamd, adjust ATRH so that the modulation is proper.

12.6 RX Carrier Detect

The DCD signal from the modem may be generated by detection of RF, using an internal signal called

RSSI (Receive Signal Strength Indication). The RSSI signal is an analog signal representing the

strength of the RF carrier. It is compared with a pre-set value, and if it is above this value, Carrier

Detect is asserted. The pre-set value may be change with the ATRA command.