Last Updated on: 01/27/2002
All of the Applications featured on these pages require
either the 2-Level FSK interface or the 4-Level FSK interface. You must
build this interface, or buy it from some of sources listed at the bottom of the
page. NOTE that these interfaces DO NOT provide computer control for your
scanner, but rather they interface the output from your scanner so that the
computer and application can decode the digital signals.
These interfaces connect to the discriminator output on you
scanner (and ONLY the discriminator output) This is usually a connection
inside of your scanner that must be made with a soldering iron.
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 all of the applications featured by this
page. Most scanners must have a simple modification made to them to output the
discriminator audio output to the interfaces outlined on this page.
- See here for a list of discriminator
output locations for many popular scanners - courtesy of Bill Cheek
- See this document
from Greg Knox regarding instructions on how to tap the discriminator output
on the BC-895 Scanner. See this picture
for the location of the discriminator output on the 895.
- See Bill Cheeks SCANDATA.FAQ listed at the bottom of the
page for detailed instructions on how to tap the discriminator in your
The 2-Level Interface
The 2-Level Interface (also called the Hamcom interface) is
required for most of the applications that are available for decoding digital
signals today. See the applications page for further information on which
interface is required for each application. There are numerous different
version of this interface, but they all accomplish the same
The most popular version of the hamcom interface.
See this picture
of how to build this interface using a Radio Shack experimenters board (thanks
to Mitch Savage KJ5NL email@example.com)
Here is a schematic of the 2-Level interface designed around
the TL082 Op-Amp. This version of the interface works very well!
(This is the version that I use, and it works wonderfully)
Here is another schematic of the 2-Level interface based
around the MAX232 chipset. This interface is very reliable and is reported
to work VERY well with Trunker and Etrunker.
The 4-Level Interface
The 4-Level Interface is a new generation of interfaces that
are required for the faster digital modes. For decoding Flex paging and
RD-LAP MDT modes, this interface will be required. The only production
application today that uses the 4-Level interface today is Pocflex. This
interface will however have further uses when APCO-25 decoding becomes
Here is a schematic of the 2-level and 4-level interface
combined into one interface.
Another version of the 4-level interface with power supply
can be found below:
Also see this link for PCB Board art work for the 4-level
FSK Decoder: http://www.users.interport.net/~carlott/projects.html
Experiences and information from folks who
have gotten the interface working, their testimonials (Tips, Tricks, FAQs, etc)
- Bill Cheek's
SCANDATA.FAQ - This is a great document written by Bill Cheek that will
basically answer any questions that you might have about the 2-Level FSK
interface and the discriminator output. It outlines processes for good
circuit design and things to watch out for when building these
interfaces. A MUST READ for anyone beginning a digital signals
monitoring project. (This was updated on 12/19/2000 by numerous
contributors..... but many thanks to the late Bill Cheek for the original
- Bill Cheek's
SCANDATA2.FAQ - This is an update to his previous FAQ, and outlines how to
resolve some of the problems that come with building these interfaces.
Also outlines some problem scanners that don't provide a good discriminator
- Bill Cheek's
4FSK.FAQ - This is a great document written by Bill Cheek that answers any
questions you might have about the 4-Level FSK interface and the discriminator
- One posted to
SCAN-L - Information from a gentleman who owns a ICOM R-7100
- One by Bill
Cheek - This is a posting from Bill when he was just getting started in
Digital Monitoring w/his scanners... ;-)
- Here is an
experience from someone setting up trunker with PRO-2006 with an Opto
OS-456, an ICOM R8500, and an OptoLinx. Here is a
bitmap of the user's setup. If you have an Opto OS-456 and the
OptoLinx.....this article written by David M. Hitchner will really help
OptoLinx and an AR8000 working with trunker/etrunker - Using 1 serial
port. Sent by MARK COLBORN [HOTSPOT@worldnet.att.net]
- Getting the Optocom
working with trunker. This is a post from Usenet from a gentleman
who was able to get the new Optocom working with Trunker. He has posted
his environment settings and procedures he used to get it working.
- Data Slicer and
AR8000 interface - an all-in-one schematic for interfacing the AR8000 with
a slicer with one circuit.
- Settings for the
AR8200 scanner - getting the AR82000 Scanner to work with trunker is
easier than you thought!
- Using the ICOM
PCR-1000 with Trunker - this article was written by Mike Curtis, and
explains how he got is PCR-1000 working with trunker.
- Getting the BC-895 to
work with Trunker - this article was written by Mike Curtis, and explains
how get got the BC-895 working with trunker and Etrunker.
- Icom R7000
Interface with new slicer type - [PDF File] Here is a schematic for an
interface used with Trunker and a Icom R7000. For this example, a
PRO-43 scanner is used to obtain the data channel. The interface obtains
power from the Icom, so there is no issue with weak ports not being able to
power the slicer. The IC Chip used is a MAX203 for minimum parts
count, but a MAX232 would work just as well. The MAX203 can be obtained from
Digi-Key. This interface has also been tested with an Icom R7100. This
interface may also work for other radios that use TTL serial levels if another
source of 9-12V is available, or 5V if the regulator is left out. (Thanks to
If you are interested in buying the interface instead of
building it, here are links to some vendors: