[sci.electronics] More Mods for the PRO 2004 !!

ewb@raybed2.UUCP (EUGENE BALINSKI) (07/08/88)

  From Monitoring Times July 88 Volume7 number 7, Page 93


   That's right folks, more mods for the '2004. Remember these mods are
done at your own risk. Have fun.
 
   In a previous posting the question of enabling 520 to 760 MHz came up.
Apparently this info was false. It cannot be done. (at least at this writing)
But  adding an "S" meter is even easier than previously thought. Pin 10
on the IF amplifier is an "S" meter output. With the  proper bridge or
meter buffer/amplifier an "S" meter is reality. But wait, there's more !!

   Turbo scan for the 2004 ??? Yes !! Someone has realized that if you 
replace the present 7.37 MHz ceramic resonator CX501, with a 10.7 MHz
ceramic resonator it really boosts the scan/search speed! The present
resonator is soldered between pins 29 and 30 of the CPU (IC-503). Rumor
has it that a 10.00 MHz computer xtal will work just fine. Note the effect
of the speed mod on weak signal performance is presently unknown.
  
Hopefully someone can/will verify that these mods work. (Bob Parnass where are
you ???) Good Listening. 
                                                          73
                                                     Gene Balinski
                                                        WA1UXA


                     <Standard Disclaimer Applies>

P.S. Be sure to UNPLUG the radio before OPENING the case !!!!
P.S.P.S. For further info see Monitoring Times Mag. I strongly suggest that
         you subscribe to this mag and read the article on the mods.


Monitoring Times Magazine
P.O Box 98
Brasstown, N.C. 28902  
PH 704-837-9200

parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S) (07/09/88)

About  the  Radio  Shack  PRO-2004  scanner,  Gene  Balinski
WA1UXA, wrote:

 >  ...But adding an "S" meter is even easier than previously thought.
 > Pin 10 on the IF amplifier is an "S" meter output.
 > With the  proper bridge or meter buffer/amplifier an "S" meter
 > is reality....
 >
 > Hopefully someone can/will verify that these mods
 > work. (Bob Parnass where are you???) Good Listening.


Despite the internal IC block diagram in the service manual,
WBFM IC pin 10 on my PRO-2004 is useful as an S-meter output
only when the radio is in the WBFM mode.

Between pin 10 and ground, I placed a 10,000 ohm resistor in
series  with  a  250 microamp meter for a simple test setup.
The meter read full scale on strong WBFM  signals.  With  no
signal at all, the meter read about 70% of full scale.

One could add a bridge, but this metering point is of  limi-
ted utility.

COR lights are handy as visual cues in a  room  filled  with
operating scanners.  Pin 13 on the NBFM IC is a good pickoff
point for triggering a COR light.  I applied the  signal  on
pin  13  through a 10,000 ohm resistor to the base of an NPN
transistor switch to  actuate  an  LED  when  a  carrier  is
present.
-- 
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Bob Parnass AJ9S,  AT&T Bell Laboratories  -  att!ihuxz!parnass - (312)979-5414