In theory I'm coming to you from across my house via light beam
communications.
[ But I wasn't, I ran into more software configuration gotchas when
moving from sending/receiving with one laptop running very old
Linux, to transmitting from my 'new' laptop running current Devuan
Linux. First was that I forgot that specifying characters as
hexidecimal codes with "echo -e" is a Bashism, so didn't work with
/bin/sh which is symlinked to /bin/bash on the other laptop. More
difficult was working out why the sending would stop after a while.
It turns out the kernel serial driver now has a default time-out of
30sec for the serial port buffer to clear before it's forced closed.
Since I was using really slow baud rates, it always timed out before
the end of the file was transmitted. This isn't the domain of stty,
so I needed to install setserial with which the time-out can be
bumped up to 20min with:
sudo setserial /dev/usb/ttyUSB0 closing_wait 120000
So now on the 6th of Feb, another warm night full of dive-bombing
mozzies, I'm having another go at sending this post through my house
and out into cyberspace through nothing more than some flashes of
light.
It did give me a chance to upload some photos of my cobbled-together
optical transmitter and receiver though:
gopher://aussies.space/1/~freet/photos/optical_comms/ ]
[ Hmm, now the receiving laptop has hung, requiring a hard reboot,
with is very unusual. I really am better off keeping computers out
of my electronics projects. Anyway, third try... ]
[ Nope, it hung again. Damn it, computers just don't like to communicate by light! ]
Except for the sun room extension, the house opens
up straight from one end to the other down the hallway, so I set up
at the furthest ends short of removing a table and cupboard, for an
8.5m transmission distance. This isn't terribly impressive, but as
far as I can get indoors, and I'm sure not going outside again
tonight if I can help it.
Today was the date of the hamfest (amature radio swap-meet) I try
to get to. Last year it was too hot. This year, too hot again. The
beginning of a forecast heatwave, and quite warm even in the early
morning. So I missed out on that yet again, having only got to one
since the pandemic. Instead I've been working out the design for
the cantenna/waveguide for attaching to my satellite dish that I'll
use as a 4G mobile broadband antenna. I'm still not sure how to
tell which of the 45 degree polarized antennas to connect to which
connector on the modem, but otherwise I think I've sorted out
everything except a 'can' of the right size and rigidity.
This was in the air-conditioned comfort of the lounge room. Later
on I tried setting up the opical transmitter and reciever units
that I built on the ex-army telescope tripods that I built them to
fit. They're both the same model "instrument stand no. 21 Mk. V",
but it turns out one's from WWI (made in 1915) and the other's WWII
(1943). So the former is about 110 years old! This is quite
possibly the first real use it's been put to in all that time
because it looks pretty unscathed for its witness of over a
century, or maybe it really was used in battle out next to where T.
E. Lawrence is in Seven Pillars of Wisdom which I'm still reading,
and quite enjoying.
Anyway I took some photos of the rig, which I can't be bothered
selecting and uploading now, to be tested out when it cooled off
and I could open up the parts of the house that the A/C doesn't
reach. Before that the weather started getting dark and I heard
thunder, so I set up my cloud charge detector again. Soon the
needle of its over-sized panel meter was bumping back and forth in
a facinating rhythum as the crashes of the heavens grew louder
accompanied by much brighter flashes than I had in mind for my
optical transmitter that night. But then a sudden jolt to one end
of the scale was triggered not by lightning, but by a sudden
powerful wave of dust blocking out everything to be seen through
the windows of the house and prolonged by a fierce wind that
continued as the meter jolted still with each nearer strike of
lightning. Suddenly a great downpour of rain came and dampened
everything with brown dirty water, giving way to hail and greater
deluges overflowing the guttering of the house. I continued to
watch the storm through the windows and my cloud charge detector
until a sudden swing on the needle to the other extreme revealed a
change in the wind had blown the rain over the sensor on the
verandah and I rushed out to grab it defore the electronics, or the
card base it's built on, got too wet. Since I was naked anyway this
was really quite a refreshing shower in the persistently warm
weather, only the passing threat of lightning and the brownness of
the puddles dissuaded me from having a splash in them too.
The storm died down and I cooked a slightly late dinner, after
which there was a fire call to a tree burning on top of a hill from
a lightning strike. I went along to that and helped with filling up
the newer fire trucks spraying the tree with their fancy
bumper-mounted monitors. Chatter on the fire radio mentioned downed
power lines and torn-off roofs in nearby towns. Someone said the
nearby fire tower had measured a wind gust to 150Km/hr. After an
hour of this the tree was out and clouds were closing in for
another storm. Nobody wanted to be on the side of that hill for a
repeat performance of that apocalyptic weather, so fire trucks soon
scattered and I got back home just before the rain began again. Not
so fiercely as it turned out, but enough that our efforts on
wetting tree may have been pointless.
At least now it's cooled off, so I can test this optical thing out.
The only trouble being that I still need to get my orders prepared
tonight to post tomorrow morning before it gets hot (if it ever
gets properly cool). I wanted to wait untill the storm passed,
which it has now, to keep my computers powered off in case of a
power surge. The mozzies are all over me too. So let's see if this
works and I'll post some more details later on, or maybe when I
finally try it outdoors for ROOPHLOCH, when I'll really be able to
find out how far it can go.
- The Free Thinkar
