To cite a specific case, the California Highway Patrol uses VHF-Low band
radios (around 45MHz). This band covers the remote mountain and desert
areas using fewer fixed sites than would be needed for VHF-High band, UHF,
or trunked systems. Longer wavelengths propagate better on
diffraction-limited paths, which is what CHP must deal with outside of the
major urban corridors. The need to communicate over difficult weak-signal
paths is one reason they stay with this "old tech" system. This is spectrum
where BPL systems operate, and where "legal" levels of interference can
prevent critical communications.
--Tim (KR0U)
"Dave Bernstein" <dave.bernstein@comcast.net>:
Every public safety or law enforcement agencies rely on wireless
communications, but most of this is VHF and above, which as I understand
it is not threatened by BPL. It would be helpful to identify those
agencies that rely significantly on HF frequencies; they should be
candidates for special attention.
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