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Cobra 200GTL DX: How to add talkback. | Radioaficion Ham Radio

Cobra 200GTL DX: How to add talkback.

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COBRA 200GTL DX How to add talkback.

The following instructions provide two options: adjustable-volume talkback and

fixed-volume talkback. Adjustable-volume talkback is more complicated to install but allows easily changing the talkback volume.

Use caution when installing talkback. The parts inside the radio are small and it is easy to cause damage.

See page 2 for fixed-volume talkback.

See page 5 for adjustable-volume talkback.

ADJUSTMENTS: None.

NOTES:

  • Talkback will work only when echo is turned on.
  • Talkback will be available through the built-in speaker or through an extension speaker.

Fixed-Volume Talkback

Parts Required

  • (1) 0.047uF (473) ceramic disk capacitor
  • (1) 1/4 watt resistor

COBRA 200GTL DX How to add talkback

Step 1: Disconnect the indicated lead of D9. Do not cut the trace, you must carefully unsolder the lead and disconnect it.

Step 2: Connect the capacitor-resistor assembly to the indicated points.

COBRA 200GTL DX How to add talkback

Step 3: Use glue to secure the parts, otherwise they will vibrate and eventually break the solder joints.

COBRA 200GTL DX How to add talkback

Step 4: Scratch the ground plane next to the speaker connector to expose the copper foil. Solder from the speaker connector to ground as shown.

This completes the modification.

NOTE: The value of the resistor can be changed to adjust the talkback volume. A smaller resistor will provide more volume.

Adjustable-volume talkback

Parts Required

  • (1) 0.047uF (473) ceramic disk capacitor
  • (1) 1/4 watt resistor
  • (1) 50Kohm panel-mount potentiometer

COBRA 200GTL DX How to add talkback

Step 1: Disconnect the indicated lead of D9. Do not cut the trace, you must carefully unsolder the lead and disconnect it.

Step 2: Pick a mounting location for the potentiometer. Try to pick a location so that the wires can be kept short. Drill a hole and mount the potentiometer.

COBRA 200GTL DX How to add talkback

Step 3: Connect the capacitor-potentiometer-resistor assembly to the indicated points.

Step 4: Use glue to secure the parts and wiring, otherwise they will vibrate and eventually break the solder joints.

COBRA 200GTL DX How to add talkback

Step 5: Scratch the ground plane next to the speaker connector to expose the copper foil. Solder from the speaker connector to ground as shown.

This completes the modification.

Cobra TECHNICAL SERVICE August 18, 2005

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