ic27.3

Original from KN4HX to ALL@FLBBS

A friend, KD4GHV, has an Icom IC27 radio and a PK88 TNC connected.
He was having a hard time receiving packets.  He was getting out OK and
other stations were sending replys but his TNC was not hearing and
recognizing the information as packet.

We thought the problem was computer interference or even interference
in the front end of the radio by the TNC itself.  We did all the necessary
filtering but to no avail.

The sound coming from the radio sounded filtered, as if the high audio
frequency was being muffled.  It was.  There is an audio filter stage, Q6,
in the audio amplifier section which limits the high frequency response.
To remove this high filtering and to start working packet radio properly
you should remove (clip one leg) of capacitor C67.  C67 is located in the
bottom side of the radio.

Remove the bottom cover.  Have the knobs pointed toward you. C67 is the 
capacitor in the left corner toward the knobs.  Don't cut anything
until you see the 'C67' label near the cap.  We cut one leg and left the
other keeping the cap in the circuit.

Use a good magnifier to see the lettering on the cap.  If you cut the wrong
part you may have to remove the printed circuit to replace the mis-cut part.

KD4GHV now can work all the packet he desires.  The radio audio was only
improved, as I hear it, with better high frequency response.

Good luck, and I hope this works, 73,

John, KN4HX, Plantation, Florida