Modifications

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These mods are extracts detailed in the following articles:

	a) POPULAR COMMUNICATIONS AUG 87, PP 18-20

	b) MONITORING TIMES OCT 87, P 53

	c) MONITORING TIMES DEC 87, P 60

I would suggest that you obtain the back issues and read through the letters
and articles.  Also that you subscribe to the magazines.  They supply a lot
of interesting scanner information as well as useful frequency lists.  Also
Radio Shack sells a technical manual on all their electronic equipment, which
contains maintenance and calibration procedures, as well as schematics.
 
Preliminaries:

	First, treat the radio as if it were CMOS.  That is make sure you take
	precautions concerning static charges.  Second, unplug the radio from
	the antenna and AC power.  Remove batteries.  Take the radio out of the
	case by removing the 4 screws on the back.  Carefully invert the radio.
	Locate a box-like sub-circuit.  It's near the switch marked "restart".
	The sub-circuit should be marked PC-3.  Carefully pry off the cover of
	the metal box.  Inside there will be a 64 pin dip IC.  This is the
	radio CPU.  Be careful not to touch or short out any leads on the chip.

1) Restoring 870 MHz coverage.

	Near the chip there will be a row of diodes marked D-502 to D-515.
	If D-513 is present, cut one lead, seperate it so they will not touch,
	and 870 Mhz is restored.  If D-513 is not there and you still do
	not have 870 coverage, then a little more work is in order.  Locate the
	9 pin connector "CN-501".  Carefully remove it from the sub-circuit.
	Remove the screws holding PC-3 to the main chassis.  Carefully invert
	the sub-circuit board (PC-3).  Locate the lone component on that side
	of the board.  If it is a diode, as it should be, then cut one lead and
	seperate them as above.  Re-install the sub-circuit with the screws on
	to the main chassis.  Reconnect the 9 pin connector.  Do NOT put the
	cover back on just yet.

2) Increasing from 300 to 400 channels

	On the top of the sub-circuit board, locate the slot for D-513.  Count
	backwards from there until you get to the space for D-510.  Install a
	diode at D-510 in the same polarity as the rest of the diodes.  You
	now have 400 channels instead of 300.

3) Increasing scanning speed to 20 channels per second

	Now install a diode at D-514 and you have increased the scan
	speed to 20 channels/sec from 16 ch/sec.

4) Improving squelch operation

	Carefully reassemble the metal box.  Make sure everything else is as
	it should be.  Invert the radio so it is right side up.  Now, locate
	a sub-circuit box under the sloping front panel.  It should have many
	alignment holes in the top.  Pry the cover off very carefully.  Locate
	IC-2 in the left side of the pc board.  It should be marked IC-10420.
	Locate R-148, a 47 K ohm resistor between pins 12 and 13.  Cut a lead
	of this resistor, But be sure to leave enough lead on both sides of
	the cut to solder to.  Patch in a 100K ohm resistor.  Make sure there
	are no solder balls or short circuits.  Now your squelch will operate
	much better.

	Again, I strongly suggest you obtain the above mentioned magazines for
	more details.

	73
	Gene WA1UXA

	PS, install the metal cover and the radio back in the case.


	Addresses:

	Popular Communications
	76 N Broadway
	Hicksville, NY. 11801
                          
	Monitoring Times
	140 Dog Branch Rd
	P. O. Box 98
	Brasstown, NC. 28902

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The above edited text received on usenet, a network of unix(tm) computers.
This modification voids your warranty.  If you don't understand electronics,
you have no business behind the front panel.  Take it to someone who guarantees
their work.  It will be much cheaper that way.

-/Vuarnet International/-
      617/527.oo91
  24oo-16.8k HST/V32bis