Wednesday, July 2, 2008

Digital radio system types

Trying to sort out manufacturers claims relating to digital radio systems can be quite a task. To eliminate some of the confusion, we have prepared the following overview on the three most common systems used in the USA. The best known is Project 25 (Also known as P25 and APCO-25). This is a full featured system that is backwards compatible (i.e., it can handle both analog and digital signals through a single station, mobile, or handheld). Currently, it can operate on 25 or 12.5 kHz channels. It is EXPENSIVE. DMR (Digital Mobile Radio) is a European standard that splits a 12.5 kHz channel into two "slots" (typically one for voice and the other for data). In the USA, the Motorola MotoTRBO system utilizes this technology. Unfortunately, the system currently is NOT backwards compatible through the repeater (i.e. the repeater can handle only analog or digital signals but not both) and it is incompatible with 2-tone paging systems in the analog mode. Neither P25 or DMR are currently compatible with single channel 6.25 kHz channel spacing. dPMR (Digital Private Mobile Radio) is the most cost effective of the three technologies with full backwards compatibility for analog/digital operation. 2-tone paging in the analog mode allows continued operation for fire department users and a simple migration process for any VHF or UHF system user. dPMR (Also known as the ICOM IDAS system) is the only technology capable of operating at 25, 12.5, or 6.25 kHz single channel or repeater operation.