Cobra 2000/148 & Uniden Grant XL ALC & AM Modulation Modification

Cobra 2000/148 & Uniden Grant XL ALC & AM Modulation Modification

Half of the following modification increases the AM modulation swing. It allows you to reduce your carrier to around 1 Watt while maintaining a swing of up to 18 Watts.

This is good for those of you who want to blast out on AM. This will also drive any amplifier to sound like an RF modulator. Setting the AMC can reduce distortion.

The other half modifies the ALC circuit allowing finer adjustment. This will allow higher peaks while staying in the ALC range.

Set properly the mic gain can be wide open without the total distortion heard when the limiter is completely removed. The changes are similar for other chassis using the 8719 PLL chip. You may be able to locate the same components by tracing the circuits.

94280

Reference shaded areas on drawing above.

  • Remove R166
  • ADD
  • 8.2 K from the emitter of TR26 to 8 volts constant.
  • CHANGE
  • R228 from 560W to 33K
  • R159 from 18K to 33K
  • CHECK
  • C109 for 10µf