Measuring distance with RF

hi

http://www.instructables.com/id/distance-measurement-with-radio-waves/step7/step-6-conclusion/

this link seems suggest use circuit send ping circuit, measure length of time taken receive reply , result accuracy of +-5m

i stumbled accross whilst playing around 2 arduinos happen have rf modems on them , thought might fun experiment, but...........

i stuck serial.prinln(currentmillis) sketch , beggining of loop. , let serial monitor run bit, 7ms loop time, flucuation.

meaning in theory ( , or practice) radio waves modules have travelled (299792458/1000) per millisecond, , since loop takes 7 times run, in no way able useful it.

is there feasibilty in using arduino , or microcontroller idea?

quote

it's easy use, it's easy built [sic], it's cheap , it's new revolutionary method of distance measurement

so revolutionary, it's been around since 1930s.

with custom hardware yes, doable, processor executes single instruction in time takes radio signal travel 18metres, +/- 5metres bit optimistic.

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