Wireless telemetry (using high voltage valves) was utilised even back in grandpa’s era.Perhaps one
of the more exotic installations was the World War II German automatic weather
station "Kurt", secretly installed on the Canadian coast by a U-boat in 1943.
Its 150W short-wave transmitter, powered by an array of
nickel-cadmium and dry-cell batteries, produced coded signals (derived from
weather sensors) receivable thousands of kilometres away in Europe. Distant
Atlantic weather conditions could then be monitored but – fortunately for Allied
shipping – jamming thwarted the station’s eventual mission!
The HopeRF module
that has Stan so excited this month! Shown here approximately life size, it operates in the 434MHz "LIPD" band and mates perfectly with Stan's other favourite toy, the PICAXE.
Modern motor racing telemetry allows trackside engineers to
view and interpret live race data and use it to rapidly tune their racecar at
eventual pit stops. When every second counts, the ability to promptly work on
tele-monitored faults can make for improved race performance.
Such "mission critical" applications usually have heavy duty
telemetry budgets but the availability of cheap data modules in recent years has
allowed UHF wireless data links to proliferate, with many homes even now having
several quietly at work – typically at 433.920MHz.
As wireless links on the higher (near microwave) 1.8-2.4GHz
bands are almost line of sight (LOS), many field telemetry setups in fact prefer
low UHF (300-900MHz) or even lower VHF (30-300MHz), as this ensures better
signal penetration of vegetation and buildings.
The popular 434MHz slot, globally reserved for low power (25
mW) unlicensed Industrial, Scientific and Medical (ISM) wireless data,
increasingly abounds with weird signals arising from home weather stations,
power meters, car locks, garage door openers, security systems and wireless
doorbells. In many suburbs at peak times, a UHF scanner tuned to 434MHz can
issue sounds akin to an African dawn chorus!