Discriminator output
From The RadioReference Wiki
The Discriminator output from a scanner is the raw, unfiltered signal that a scanner produces before it is sent to the audio stage for output through the speaker -- also called the "baseband audio." This discriminator source is required for applications such as Trunker, T4Win, UniTrunker, and DSD. Most scanners must have a simple modification made to them to feed the discriminator output to Data Slicers, or in the case of UniTrunker, a soundcard.
Note that for providing a signal for ACARS or MPT-1327 decoding, a connection from an earphone or speaker output is all that's required. This is because these modes run at a much lower speed, and the discriminator is not involved in AM reception (for ACARS decoding).
Modifications
Also see the Scandata faq q2 article for a list of older scanners' tap points. This is from an original article written by the original scanner hacker and guru the late Bill Cheek.
Uniden
- BC-245 Discriminator Tap
- JPEGs of BC246 discrim tap
- BC296D/UBC 3300XLT
- BC350A Discriminator Tap
- BC350C Discriminator Tap
- BC-780 Discriminator Tap
- BC785D Discriminator Tap
- BC796D Discriminator Tap
- BC895XLT Discriminator Tap
- BCD996 Discriminator tap point
- BCT15 Discriminator tap point
- NOTE: Look dead center of the circuit board, then go right and down. Both the 996 and BCT15 appear to share the same tap point location.
Radio Shack
- Pro-26 Discriminator Tap
- Pro-93 Discriminator Tap
- Pro-95 Discriminator Tap
- Pro-96 Discriminator Tap
- Pro 97 Discriminator Tap
- Pro-106 Discriminator Tap
- Pro-164 Discriminator Tap
- Pro-2052 Discriminator Tap
- Pro-2053 Discriminator Tap
- Pro-2066 Discriminator Tap
Other Radios
Why use a resistor and/or capacitor ?
See #6 through 8 of this URL: Discriminator.nl FAQ
Wikipedia Page showing Circuit and calculations for Discriminator Tap.
Related Pages
These pages or links contain more information on discriminator taps for many brands and models of scanners, including older models