Welcome to the Midwest Quantar Bridge Site

Welcome to the Midwest Quantar Bridge Site This site is dedicated to advancing the art of linking Motorola Astro25 infrastructure via legacy V.24 serial connections, over modern internet connections to a software based Comparator/management system. We use TCP transport with engineered error correction, the way it was originally designed.

We will present the equipment needed, the connection diagrams, expectations of operation, and describe research done by many people which led to successful decoding of the V.24 protocol used by Astro25 Fixed Network Equipment (FNE) such as a Motorola Quantar or AstroTAC Receiver.

Diagrams presented will be based on a common set of equipment, and sources for acquiring such equipment at nominal cost.

In normal operation of P25, predefined "TalkGroups" are utilized to segment traffic and this project allows both local traffic to remain on their originating source, and a "Zoned" logical arrangement for Comparator voting or larger coverage. This differs from other digital technologies where a flat TalkGroup-only scheme is in operation.

Topics of discussion to be found on this site include:

  • Concept and Overview
  • Hardware suggested and used in actual operation
  • Protocol Discussion - HDLC/STUN/V.24
  • V.24 Fields decoded and their uses
  • How does RT/RT linking work?
  • MQB TalkGroup Zoning Methodology
  • RSSI Voting (Software Comparator)
  • Issues seen with using the Public Internet as a transport
  • Brick Wall filtering for poor signal conditions, and what Silent Frames provide
  • MQB Program Block Diagram and System Layout (Server, DB, Web)
  • Separation of Input and Output data streams and their benefits

    • This site in being continuously populated with data, so please check back often for new information!