About a year ago I was forced to deal with a use case for a 900Mhz
transceiver putting roughly 20mW that called for it to be inside an
aluminum beer tap handle. It was astonishing how well it worked, with a
range of a couple dozen feet. But it had a large hole in the end, and it
was driving a full size dipole antenna, not the little chip antennas or
zig/zag PCB quarter waves the folks on this list are likely to be
using. A closed metal mailbox would pretty much guarantee frustration.
-Pete AD4L
On 1/8/20 11:33 AM, Brian via TriEmbed wrote:
On 1/7/20 10:43 PM, Glen Smith via TriEmbed wrote:
I'll add my welcome to Brian's, and add a +1 to most everything he said.
The only additional insight I hope to add would be that you may very
well be able to add a small solar cell to the top of your mailbox
Great idea! And very likely the complete answer to the power
question, since the device will only be awake a tiny fraction of the
day, as you pointed out.
You biggest problem may be transmitting through the Faraday cage of
the mailbox.
Faraday cages aren't very effective when they aren't grounded. If the
mailbox doesn't have continuity to Earth (on a dried-out wooden post,
maybe), it won't attenuate the signal as badly (RF power will still be
lost by induced eddy currents in the metal, but the metal won't be as
reflective as it would be if grounded).
That said, all you really have to do is get the antenna outside the
box. It shouldn't be too hard to find an Arduino-friendly RF module
with a connector (SMA or UFL) instead of an onboard antenna; then a
short cable and "rubber duck" antenna mounted outside the box is all
you need.
-B
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