Simplex Operations and Equipment
Equipment
A "weak signal" rig is recommended for the primary NCS because its improved sensitivity brings in fringe stations those typical FM mobiles can't even hear.
All-mode transceivers which don't receive outside the 2-meter band are less susceptible to intermodulation distortion. EmCom must be able to operate in high RF environments in close proximity to emergency services, hospital paging and other users. CTCSS reduces interference, but when the squelch is open RF mixing products can still get in.
In Virginia, RACES experience Par Electronics notch filters (http://www.parelectronics.com/amateur.htm) work better for IMD suppression in typical EmCom applications than the DCI helical cavity band pass.
These are compatible with dual-band rigs. with low VSWR, transparent UHF pass-through, and are effective when a strong near-field source de-senses typical mobile transceivers. In tests conducted at Fair Oaks Hospital. 2-meter simplex contacts were reliable to 15 miles away, impossible with the DCI "can" used in the same high-RF environment. Low-loss UHF pass-through enabled UHF simplex contact between hospitals within a ten-mile radius of the "Command hospital" during the Dulles Disaster 2000 Exercise.
Dual-band rigs are desirable, because UHF is more effective than VHF in built-up urban areas.
Use dual-band mobiles in cross-band repeat with CTCSS as access control to conduct nets from within shelters or hospitals and to reach into low areas with poor simplex coverage.
The 220 MHz band is quiet, less affected by intermod than 2 meters.
It gets out of buildings well and has good simplex propagation. If you have enough operators with 220 capabilities, you include it in your operating plans.