RS Pro-89 volume mod?
 

"LoneGunman" wrote in message
...

Can the Radio Shack Pro-89 be modified for more output volume? with 2
pair of headsets, it could use just a bit more power. If so, any online
how-tos?

That's the negative side of hand held scanners. I've used small amplified
speakers made to be used with walkmans. I haven't bought any recently so
can't tell you exactly where to get them but feel quite sure they are still
available. They do make a hand held sound like a real radio. RM~

PS I might add , my only experience with hand helds are, Pro-34, Pro91 and a
Pro94. It's quite possible that some of the others may sound like "Real
Radios".

Most can be modified by putting a small jumper wire, from the ground side of
the antenna, to the ground side of the earphone jack. Many of the earphone
jacks have a resistor, in series, on the ground side. Shorting this out to
true ground, gives you full output. This is a protection device, so people
don't damage their ears.

Bill Crocker


"LoneGunman" wrote in message
...
Can the Radio Shack Pro-89 be modified for more output volume? with 2
pair of headsets, it could use just a bit more power. If so, any
online how-tos?

Thanks

Bob Parnass published a mod for the PRO-43
years ago that provided a significant boost to
the high-frequency response of the audio amp.
A lot of scanners' audio is too bassy. To get
decent volume, you have to turn it up and then
the excess bass overloads the amp. By boosting
the highs, you don't need to use as high of
a setting to get the same perceived volume.

What the mod did was to remove a bypass cap
from the input of the audio amp chip, thereby
letting the amp chip amplify the high frequencies
that would never normally make it through
to the speaker.

If you can find the amp chip in your scanner, do
a google search for the chip number. Get the
pinouts. Look for a bypass cap on the input of
the audio amp chip and remove it. The cap is
usually a .015 to .001 mfd 0603 size surface mount
part.

I've done this mod on many scanners, and the volume
is usually satisfactory afterward.

Good Luck

(All credit for this mod goes to Mr. Parnass!)