Page 8

3.4.2 Transmit audio path verification

a. Using an audio signal generator, set for a 1KHz sine wave at 300 mVrms, connect the audio

signal generator to TXIN.

b. Connect an oscilloscope or audio analyzer to TXOUT.

c. Measure the output level and calculate the gain difference between TXIN and TXOUT.

20*log Vin/Vout where Vin = TXIN and Vout = TXOUT.

d. Calculate the level that represents -3 dB below the output level at TXOUT for a 1khz sine

wave.

10

3

20





dB

e. Lower the frequency of the signal generator until the -3dB level is reached.

f. Measure the output frequency of the signal generator. This will be the lower -3dB band edge of

the TX audio filter.

g. Raise the frequency of the signal generator until the -3dB level is reached.

h. Measure the output frequency of the signal generator. This frequency will be the upper -3dB

band edge of the TX audio filter.

h. Remove ground from PTT . The 1KHz signal applied to TXIN should not be present at the

TXOUT connection.

3.4.3 CTCSS decoder verification

a. Remove ground from PTT .

than 3 volts dc.

c. Connect an audio signal generator to RXIN. Adjust the audio generator’s level to 50 mVrms

and its frequency to equal the CTCSS tone frequency (

using Table 4: CTCSS Tones starting on page 17.

0

output. It should be less than 1 volt dc when

detecting a CTCSS tone.

0

output should go to a hi logic level

(>3VDC).

3.4.4 Receive audio path verification

a. Ensure PTT and PTL is not connected to ground.

b. Using an audio signal generator, set for a 1khz sine wave at 300 mVrms, connect the audio

signal generator to RXIN.

c. Connect an oscilloscope or audio analyzer to RXOUT.

d. Measure the output level and calculate the gain difference between RXIN and RXOUT.

20*log Vin/Vout where Vin = RXIN and Vout = RXOUT.

e. Calculate the level that represents -3 dB below the output level at RXOUT for a 1khz sine

wave.

10

3

20



f. Lower the frequency of the signal generator until the -3dB level is reached.

g. Measure the output frequency of the signal generator. This will be the lower -3dB band edge

of the RX audio filter.

h. Raise the frequency of the signal generator until -3dB level is reached.

i. Measure the output frequency of the signal generator. This will be the upper -3dB band edge of

the RX audio filter.

j. Connect ground to PTL. RX path audio should not be present at the RXOUT connection.