Adjusting The Crystal Reference; Checking The Receiver Parameters; Checking The Transmitter Parameters - Adcon A440 Technical Reference Manual

Table of Contents

3.3.10. Adjusting the Crystal Reference

1. Switch the unit to transmit mode by entering TX at the terminal.

2. Observe the indication shown by the Service Monitor: adjust R75 (see

1. Switch the DUT to receive mode by entering RX at the terminal.

2. Switch the Service Monitor to RX TEST mode, on the appropriate frequency

3. Verify that the S/N ratio is at least 12 dB; in addition, if a scope is also

4. Switch the DUT to pulsed mode by pressing the Enter key. After several

5. Switch the RF generator output off.

6. Verify that the RSSI threshold is correct by typing the command RSSI; the actual

If any of the above targets are not reachable, visually verify ﬁrst that the U8 chip is

correctly soldered and that there are no shorts between its pins (most problems usu-

ally appear around this chip).

1. Switch the DUT to transmit mode by typing the command TX 0 at the terminal.

2. Switch the Service Monitor to TX TEST mode, on the appropriate frequency

• No parts are missing, or have the incorrect value, or are badly soldered (check

the parts around U2 and U10).

Figure 17) until the carrier frequency indicates 435000000 (Band 1), 445000000

(Band 2), 455000000 (Band 3), or 465000000 MHz (Band 4) ± 200 Hz,

respectively.

(435 / 445 / 455 or 465 MHz respectively); the level should be -118dBm (see

also "Test Equipment Settings" on page 34).

connected, a clear 1 kHz sine wave should be visible, with a relatively low

amount of noise superimposed.

seconds, you will see the image on the scope pulsing at about one-second

intervals.

value must be lower than the threshold set. If this is not the case, repeat the

RSSI command several times—perhaps the frequency is in use (a radio receiver

set on the operating frequency would help detect foreign transmissions). If the

threshold difference is marginal, it must be increased by using the RSSI

<value> command (it must be 20 to 30% higher than the actual value).

(435 / 445 / 455 or 465 MHz respectively). You should see the following

parameters on the Service Monitor readout:

a. Carrier: 435000000 ± 200 Hz (or 445000000 / 455000000 / 465000000

respectively)

b. Output Power: 26.5 dBm (+ 0.5 dBm / - 1 dBm)

Adjusting the Crystal Reference

Table of Contents