Xref: utzoo rec.ham-radio:5311 sci.electronics:3257
Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!ncar!oddjob!gargoyle!att!ihnp4!ihuxz!parnass
From: parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S)
Newsgroups: rec.ham-radio,sci.electronics
Subject: Re: More Mods for the PRO 2004 !!
Summary: S-meter tip of limited utility
Keywords: More Fun, TURBO, S Meter
Message-ID: <3064@ihuxz.ATT.COM>
Date: 9 Jul 88 04:15:56 GMT
References: <1193@raybed2.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 34



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