Which Freqs work best in built up areas

[CharlesHarris]

In the US our public safety radios used by police, fire and emergency medical services typically use APCO25 digital protocol on the 800 Mhz band. When operating in a steel reinforced concrete and steel high-rise office building, if there is not a nearby remote receiver for the trunking repeater system, direct unit-to-unit simplex "talk-around" is limited to about 8-10 vertical floors, with a 3-watt portable.

The former analog FM "high-band VHF" radios in the 154 Mhz band operating under similar conditions would only be reliable for 4-6 vertical floors.

Outside the building and operating in the street, the P25 800 Mhz. radios, in talkaround mode are reliable in and around an incident site for about a 10-block radius, whereas the 154 Mhz analog portables were LC solid-copy for 6-8 block at very best, but in the worst case you would have "dead" spots where the receiver of the portable would be desensed by strong nearby transmitters from digital paging, etc. and you couldn't communicate at all.

Away from the city and out in the suburbs the 154 Mhz analog radios worked wonderfully. We used a linked network of six remote receivers, a Motorola SpectraTac voting system and one 200 watt main site transmitter to cover a metropolitan area of 500 square miles. To cover the same area using 800 Mhz APCO25 digital required SIX digital spread-spectrum repeaters and 26 remote receivers and a ten-fold expenditure for equipment rack space and infrastructure...

When I first got out of the US Navy in the mid 1970s and was employed with the public works dept. our work trucks used "low-band" VHF in the 44-48 Mhz FM band, having crystal-controlled 200-watt GE radios which required dual batteries, a marine alternator, an isolator and Perko switches to keep the headlights from dimming upon full key-down. No repeaters were required and mobile units out in the country could talk directly to the Virginia EOC in Richmond from the suburbs of Washington, DC around the 495 beltway.

The new technology is said to be an "improvement". In profit margin for the people selling LMR equipment and lobby for Federal Homeland Security Preparedness Grant funds, perhaps...