Re: Radio controlled switch

On Mon, 19 Jun 2006 07:36:11 -0500, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Mon, 19 Jun 2006 03:54:01 -0400, "James Thompson"
<Jamesthompson2002@xxxxxxxxxxx> wrote:


"Melodolic" <a@xxx> wrote in message
news:JvUkg.87603$wl.69091@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I want to switch a light (or a circuit controlling a light) on and off from
a distance of nearly 20km. There is line of sight between the two
locations,
across a valley. The set up is to be used for a one-off experiment in the
UK, and is expected to last about an hour. I don't have a ham licence (but
did do the non-morse course years ago), so suggestions for licence-exempt
frequencies are welcome.

Both items need to be carried - by human - to locations in countryside and
operate on batteries, so I need a sensible size (no car batteries!) for
each. The receiver's location is several miles from the nearest road. It
would be good if the transmitter was a small pocketable hand-held device -
I
want to be able to operate a camera between switching the light on and
off.

My thoughts thus far are some sort of CW transmitter, with the actual
keying
being done using a PIC (I have some experience coding PICs, and making a
working cct shouldn't be an issue). The receiver would listen for the
series
of pulses (say, morse for ON and OFF), and respond accordingly.

Doing metalwork for making antennae is no problem - provided I have some
idea of the shape(s) I need. On the assumption that the licence exempt
frequencies are low power, would I be right in thinking that a directional
transmitter antenna would be a good idea?


--
Melodolic Spielberg


Just another thought: If radio is what you need, then look into the little
FRS style of 2 way. They have a range of about 2 miles and they are not
very expensive, plus you wont need the license to operate it.
You could have your light sound activated from the radio speaker.

---
The OP asked for "nearly 20km." Your "2 miles" falls a little
short.

Line of site they have been known to make contact at 50 or more
miles under ideal test conditions. Using dtmf tones might be a
way to control several switches.
.

Relevant Pages

  • Re: Radio controlled switch
    ... The receiver's location is several miles from the nearest road. ... My thoughts thus far are some sort of CW transmitter, ... Doing metalwork for making antennae is no problem - provided I have some ... On the assumption that the licence exempt ...
    (sci.electronics.basics)
  • Re: Radio controlled switch
    ... The receiver's location is several miles from the nearest road. ... My thoughts thus far are some sort of CW transmitter, ... Doing metalwork for making antennae is no problem - provided I have some ... On the assumption that the licence exempt ...
    (sci.electronics.basics)
  • Radio controlled switch
    ... I want to switch a light on and off from ... My thoughts thus far are some sort of CW transmitter, ... Doing metalwork for making antennae is no problem - provided I have some ... On the assumption that the licence exempt ...
    (sci.electronics.basics)
  • Radio controlled switch
    ... I want to switch a light on and off from ... My thoughts thus far are some sort of CW transmitter, ... Doing metalwork for making antennae is no problem - provided I have some ... On the assumption that the licence exempt ...
    (uk.radio.amateur)
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