Cherokee Radios CBS2100
Documentation Project
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RECEIVER ALIGNMENT

Note: Unless otherwise specified, keep the RF Signal Generator output level as low as possible (e.g. 1uV) to avoid AGC action. Make sure that RF Gain control on the front panel is set to fully clockwise position, and Compander OFF for all the following tests.

A. AM Sensitivity adjustment

1. Set AM signal generator to 27.205MHz with 30% AM modulation.
2. Set the Radio Under Test to CH-20, by rotating the Channel selector.
3. Set to AM mode by rotating the mode switch.
4. Adjust L3, L4, L6, L7, L8, L10, L11 and L12 for maximum audio level reads on the AF VTVM with 8 ohms dummy load across the terminal of speaker output
5. After completing adjustment [4] of above, repeat adjusting L8 for the balanced sensitivity on the Ch.1 and Ch.40.
6. Adjust audio output of the radio to 0.5W, check sensitivity of the receiver is better than 1uV at 12dB SINAD.

 

B. SSB Sensitivity Adjustment

Note: AM Sensitivity checks need to be completed property before proceeding to SSB sensitivity adjustment.

1. Set RF signal generator to 27.206MHz, output level 1uV without modulation for USB adjustment.
2. Set the Radio Under Test to CH-20, by rotating the Channel selector.
3. Set to USB mode by rotating the mode switch.
4. Set Clarifier control to center. (Note: ±30° of the control setting is allowed to obtain optimum sensitivity level for 0.24uV 12db SINAD.)
5. Adjust L-13 and L-14 for maximum audio output.
6. To ensure proper alignment on USB and LSB both, repeat above steps on LSB mode on frequency 27.204MHz.

 

C. Squelch Adjustment

1. Set the Radio to AM mode.
2. Set the RF signal generator to provide RF output signal level to 48dB (251uV) with 1 KHz 30% modulated. Rotate squelch control to the fully clockwise position.
3. Connect the oscilloscope to External Speaker jack, adjust VR-4 until the audio output just disappeared on the scope, indicating the squelch circuit operates.
4. Adjust the Squelch control on the front panel, check the squelch circuit will operate within 48- 70 dB on AM and SSB mode.

 

D. Compander (CDS) Functional Test - Receiver

1. Set the Radio to AM mode, Compander (CDS) OFF.
2. Set the RF signal generator to provide RF output signal level to 0.1uV with 1KHz 30% modulated. Observe Audio output from the radio at Extemal Speaker, Switch Compander (CDS) ON, observe the audio output at the External Speaker DECREASES from previous level. (Super CDS adjustments will not affect the result of this test)
3. Set the RF signal generator to provide RF output signal level to 1uV with 1KHZ 80% modulated. Cornpander (CDS) OFF. Observe Audio output from the radio at External Speaker. Switch Compander (CDS) to ON, observe the audio output at the External Speaker INCREASES from previous level.