N2CBU's Technical Information Resource

... as always, under construction ...




Icom R71A Squelch Improvement Modification

On the "Main Unit" PCB:

  1. Replace R154 (3.3M) with a 4.7M resistor.   (This adjusts the squelch delay.)

  2. Replace R153 (47k) with a jumper.  (This adjusts squelch hysteresis.  Increase the resistance for greater hysteresis.)

  3. Replace R152 (10k) with a 2.2M resistor.  (This adjusts squelch sensitivity and affects delay.  Increase the resistance for more sensitivity.)

  4. Replace C118 (0.022uF) with a 0.47uF polyester or other low-leakage non-polarized capacitor.  (This adjusts the squelch delay.)

  5. Replace D66 (1SS53) with a 1N34 or similar Germanium small signal diode.  (This increases small-signal squelch sensitivity, the lower the Vf of the diode the better.)

NOTE:  The values specified provide approximately a "two seconds plus the AGC” delay before the squelch closes.

That's all for now...  12-January-2001.