Ericsson 19D902783G1 Скачать руководство пользователя

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MAINTENANCE

TEST PROCEDURE

Following is a test procedure of the module to verify

proper Conversion Gain :

Supply 12 Vdc to pin 15A, B, C. (1C is ground.)

Inject the desired RF Frequency into RF IN at a level
of -10 dBm.

Inject the desired local oscillator frequency into LO
IN at a level of 0 dBm [LO frequency = RF frequency
- 21.4 MHz (for groups G9, G10), or, LO frequency
= RF fre 21.4 MHz (for groups G6, G8,
G11, G12)].

Measure the IF OUT power at 21.4 MHz, the ratio of
RF IN to IF OUT should be -1.5

1.5 dB.

Measure the current drawn by the RXFE module.
Typical current drain is 180 to 230 mA.

ALIGNMENT PROCEDURE

Alignment for the Receiver Front End module consists

of tuning the five-pole Preselector Filter only. The Image
Rejection Filter and LO injection filter are not to be tuned.
Normally, the RXFE should only need the fine-tuning pro-
cedure. For a major receiver frequency change, the RXFE
should be adjusted using the major-retuning procedure.

For Fine-Tuning

Supply 12 Vdc to pin 15A, B, C. (1C is ground.)

Inject the desired RF Frequency into RF IN (J2) at a
level of -10 dBm.

Inject the desired local oscillator frequency into LO
IN (J3) at a level of 0 dBm [LO frequency = RF
frequency - 21.4 MHz (for groups G9, G10), or, LO
frequency = RF frequency + 21.4 MHz (for groups
G6, G8, G11, G12)].

Detect IF signal at 21.4 MHz. Slightly adjust L1 to
L5 to get maximum power (don’t adjust more than
1/4 turn). If an RF Voltmeter is used, connect a Low
Pass Filter (LPF)to the IF OUT (J4) to attenuate high
frequency components. The corner of the LPF should
be set for 40 MHz.

Repeat Test Procedure steps to verify conversion
gain.

For Major Retuning

The best way to do a major retuning of the RXFE is with

swept frequency tuning. The swept frequency tuning can be
done using a Spectrum Analyzer and Tracking Generator.
With proper Injection level the frequency response of the
Preselector Filter can be seen by viewing the RF to IF port
feedthrough on the spectrum analyzer. This feedthrough is
typically 35 dB down from the input level at the RF port. Use
the following procedure for swept frequency tuning:

Supply 12 Vdc to pin 15A, B, C. (1C is ground.)

Inject the Tracking generator output at 0 dBm into
the RF IN connector, (J2).

Inject local oscillator power at 0 dBm into the LO IN
connector, (J3) [LO frequency = RF frequency - 21.4
MHz (for groups G9, G10), or, LO frequency = RF
fre 21.4 MHz (for groups G6, G8, G11,
G12)].

Preset the height of slugs with respect to the top of
five-pole cavity as follows (Table 2):

Center the spectrum analyzer at the desired frequency
and set the reference at about -30 dBm. Adjust L1 to
L5 for best possible response.

SYMPTOM

AREAS TO CHECK

READING (TYP.)

LOW CONVERSION GAIN

Check Vcc

12 V

Preselector Loss

3 dB

Preamplifier Gain

11 dB

Image Rej. Filter Loss

2 dB

1st Mixer Conversion Loss

7 dB

FAULT INDICATOR LOW

Check Vc of Q1

9 TO 10V

Check Vc of U2

5 TO 6 V

Check Vc of Q8

9 TO 10 V

IF FREQUENCY OFF

Check L.O. FREQUENCY

L.O. frequency=RF frequency - 21.4 MHz (G9,G10)

+ 21.4 MHz (G6, G8, G11, G12)

LOW L.O. POWER*

Injection Amplifier Gain

approx 20 dB Gain

Injection Filter Loss

2 dB

NOTE: For troubleshooting the gain or loss, the RXFE needs to be under the normal operating condition:

•

12 Vdc supply.

•

Inject L.O. power at a level of 0 dBm into LO IN (J3), [LO freq. = RF freq. - 21.4 MHz (G9, G10)
or, LO frequency = RF fre 21.4 MHz (G6, G8, G11, G12)].

•

Inject the desired RF signal at a level of -10 dBm into RF IN (J2).

•

Terminate the IF OUT (J4) with a good 50 ohm impedance.

•

Use a Spectrum Analyzer and 50 ohm probe (with good RF grounding) to probe at the input and output of
each stage to check its gain or loss (see schematic diagram).

TROUBLESHOOTING GUIDE

G6 & G11

HEIGHT (in inches)

Frequency

(MHz)

403

12/64

10/64

12/64

13/64

12/64

408