Land Mobile Radio Greatest Disappointment

by Fred Daniel

Land Mobile Radio [LMR] started out with large vehicular mounted radios, basically the same radio as the base station, just powered by the vehicle battery instead of 110 VAC. This allowed the mobile and base station coverage to be the about the same.  Over time, with improvements in technology the mobile radios became smaller and opened the door to ever smaller hand-held radios.  Today, most radio users prefer hand-held radios over vehicle mounted radios because it allows greater mobility and flexibility. However, except for very expensive Public Safety systems, most LMR users complain about the poor talk-back coverage of their handheld radios.  Many users have been forced to carry a cellular phone as their communications backup.

Cellular systems do not suffer with this problem, even though the cellular phones operate at a small fraction of the power of a LMR handheld. This occurs because the cellular industry discovered more than 30 years ago that a second antenna & diversity receiver was necessary at each cell site, to compensate for the variations in receive signal due to low handheld transmit power, signal multi-path and reflections. The addition of a second antenna & receiver adds a small incremental cost to the overall system but makes a huge improvement in reception.  

Today after several decades of field proven use, manufacturers of  LMR repeaters still do not routinely offer a second diversity receiver, to compensate for the unbalanced coverage between handhelds and repeaters.  Manufacturers continue to offer the most basic hardware because there is no unified voice in the LMR community to demand this simple but effective enhancement, like there is in the cellular industry. When this issue is brought to the manufacturers, they say no one requests this option and they offer the use of a more complex multi-receiver voter system to provide this feature. This does work but since it is not integrated into the basic repeater, the cost is often greater than the repeater itself. 

Users in the LMR marketplace need a unified voice in the form of an association of users to advocate at the FCC and to speak to the LMR marketplace.  Otherwise the LMR users will continue to only get the technology enhancements the manufacturers are willing to offer up, regardless of the general availability or need.  This was proven out by manufacturers offering the more expensive digital radios as the path to the future, rather than simply adding diversity receivers at the repeaters, which they are reserving as an enhancement to their digital product line offering, and only when necessary.  Analog FM still has a lot of useful life and equal coverage if properly implemented, at a small fraction of the cost of any digital solution.