Re: Exploding pagers

On Sat, 21 Sep 2024 11:03:39 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Thu, 19 Sep 2024 14:07:33 -0700, john larkin <jl@650pot.com> wrote:
>
(chomp)

It was probably detonated by some special message, and wouldn't have
worked on a plane.

>
Not all that special.  Pagers made since about 1990 all included a
"group call" feature, where all the pagers in a pre-programmed group
activate simultaneously.  It's normally used to broadcast
announcements:
<https://help.yeastar.com/en/p-series-appliance-edition/administrator-guide/set-up-a-one-way-paging-group.html>
I'm old enough (76) to have been involved with pagers since they
looked and weighed like a small brick and were full of germanium
transistors and vibrating reed tone decoders.

They still needed some way to fire the detonator, sort of a spare port
pin on the uP or whatever is in the pager.

>
Pagers and cell phones have problems on airplanes.  The older airplane
have an aluminum outer skin, which acts as a partial shield.  Current
model airplanes are full of carbon fiber, which acts as an RF absorber
and is actually more effective at blocking RF than a patchwork of
sheet aluminum. 
>
However, that's not why pagers (and cell phones) have problems on
airplanes.  Pagers do not tolerate co-channel interference very well:
<https://en.wikipedia.org/wiki/Co-channel_interference>
At almost any altitude, the pager is hearing many pager transmitters
and cell sites, many of which are using the same frequency or channel.
The receiver becomes either overloaded or the data becomes garbled by
the resultant interference.  I have that problem in the hills where I
live.  While the view of Silicon Valley from the top of the local
peaks is impressive, the pager and cellular performance is dismal or
non-existent.  I can be within maximum range and line of sight of the
desired transmitter, but the pager doesn't respond and the cell phone
claims it has "no signal" (which really means it has an excessively
high SNR (signal to noise ratio).  The only ways I can make such
devices work at altitude is with a directional antenna or moving to a
less impressive location.  Basically, the paging (and cellular)
systems were not designed to operate in the very crowded RF
environment found in an airplane at altitude.
>
I've been randomly watching various YouTube videos in a futile attempt
to obtain accurate information on the technology used.  Literally,
every video was useless. 
>
For example, many experts are claiming that pagers are no longer used.
It's not what it used to be before the 1990's and introduction of cell
phones, but they certainly are quite common if you know where to look.
For a time, I was selling pagers modified to close several relay
contacts.  They were used for everything between wireless rebooting a
computer to turning on/off equipment.  The local fire department uses
both pagers and walkie-talkies.  The pagers predominate because they
are cheaper.  Some of the voice pagers include storage for recording
the last dispatch so it could be replayed. 

A pager controller chip with relay driver outputs would be ideal as
the booby trap.

>
The Icom IC-V82 walkie-talky is a different story.  The IC-V82 does
not come stock with a paging (POCSAG or Flex) decoder.  It could be
used to provide a paging function with the addition of either the
optional UT-108 DTMF decoder or the UT-118 DSTAR digital voice and
decoder.  In order to "group call" these radios, the handhelds would
need to be part of a DSTAR radio repeater network.
<https://www.manualslib.com/manual/1038044/Icom-Ic-V82.html#manual>
<https://www.manualslib.com/manual/1038044/Icom-Ic-V82.html?page=12#manual>
Note that this my guess(tm) as to how it was done with the IC-V82 and
should not be considered authoritative.
>
I could write a long rant on explosives and other "amazing facts" from
online experts, but I don't want to write anything that might be
construed as bomb making instructions.  Sorry.