So in the stuff called life, I lost
my wallet. I lose things all the time.
So I tried to make a tracking transmitter
with things that I have sitting around here
because there is zero dollars.
I have a weather station transmitter that sends
out a digital pulse once a minute on 434.92 Mhz.
It has some things going for it. It runs for more
than a year without running down the 2 AAA batteries
that are in it. I can hear the pulse on in ICOM IC-R2
pocket sized scanner/receiver. But the pulse is very brief.
I can live with that. But the signal is digital and is spread
out over a MHz or so. Really really hard to track. Still fun
to experiment with. At least the batteries don't run down
for a long time.
So I looked around the junk pile that I still have here -
and found a 49 MHz walkie talkie. I put a rechargable
"9 volt" battery on it, took the mic/speaker off, and shorted
the transmit switch and shorted the switch that makes an
audio tone. This was really good. With a 2 inch antenna
on it - it went about 10 or 20 feet. Perfect in a house.
You just walk around until you hear it, and when the signal
strength indicator gets up to pin, you have it. It's about
the size of a pack of cigarettes, but that doesn't matter.
BUT, the thing only runs for about 10 hours.
So - what I was thinking - was - find the minimum voltage
the thing runs on - and it won't be drawing much current -
hopefully. Then try that and see how long it goes.
If that works, make a battery pack with MORE voltage,
and put it on a circuit like a regulator or something and
it will run longer (will it?) as the battery voltage slowly
drops down from the max value to the minumum operating
voltage value. Maybe it will go a week or so, which I
can live with. Maybe it will go longer. Who knows?
So if you guys have any ideas about this or any other
ideas let me know.
This is for a purpose, but it's for fun, too.
By the way - I found my wallet - but only
after I had replaced most of the stuff in it.
Bruce
But Bruce, even if you have sophisticated tracking equipment, you will be looking around asking everyone, "Have you seen my sophisticated tracking equipment?"
You will be alright as long as it isn't you who gets lost.
We have a man in the lost and found department here at the Internet Building answering to the name of Bruce.
And yes. I need a tracking transmitter to
find the receiver that is tuned into the original
tracking transmitter.
Yeah, it's really that bad.
Anyhow, I'm gong to be messing
around with the experiment.
But first you have to show me how
to walk all the way home from the
Internet Building. I'll need a big map.
Bruce
The map has been lost but we're tracking it now.
So I took the 49.83 MHz rig
and put a 12 volt (8 AAs) pack
on it.
We'll see how long that goes.
It's transmitting an audio tone.
Again, I find this to be fun.
Where is my wallet now?
Oh yeah, I haven't bought a
new wallet yet.
Bruce
So as I walk back to Hartford, CT
from the St. Louis area - I will drag
a big tarp behind me that is the
color orange.
Carl, maybe you can tune in a
weather satellite or something
and see me.
Meanwhile the 49 MHz rig continues
to run. I started it at 6:13 PM local
EST Hartford, CT time (12/5/14.) When will it
stop going? Any guesses?
I don't know what current it's
drawing. If I can find an ammeter
around here, I can do the calculations.
Bruce
So that's what happening
right now with 8 used AA
batteries running into this
49.83 MHz "tracking transmitter."
The batteries aren't new, so I can't
make any precise calculations for
how long they will last yet. I also
don't know how low the voltage goes
until the transmitter stops working.
But that's part of the fun.
This is the kind of stuff I used to do
when I was a kid. (If I had a variable
power supply it would be easier, but
mine quit a while back.)
Bruce
The war criminals in office place tracking transmitters underneath people's cars next to the exhaust pipe... it's been reported in news articles.
How do those transmitters work? Do they put out a beep like in the movies?
Who are the engineers who do that kind of work? Do they have any friends or social life?
There are peacetime uses of tracking technology... like tracking wolves in the wild to see where they go.
Birds and marine animals are tracked.
My trackers hate me because I never go anywhere.
Actually I don't think
anyone is tracking me. There is
nothing to know.
So, just because I was bored (again)
I took most of the batteries out of the
holders and brought the voltage down
from 12 down to 4.5 volts. After reducing
the voltage this much, the transmitter still works,
but wants to draw 20 mA. That's too much. There
is an LED running on the board. I might pull
it off and see if the current drain goes down a
little bit more. It should, of course.
If the AA batteries are say, 2000 mA/hr, they
would be good for 100 hours - or 4 days.
I wonder if I'm not right. In any case the
"around 4 days" figure is not long enough.
Oh well, it's all good cause it's just fun.
Bruce
Years ago I received as a gift a thing called a key finder. It was a small fob which attached to a key ring. Clapping your hands four times triggered a beeper in the fob with the idea being that you could follow the sound to your "lost" keys. It worked as intended but I quit using it because I almost never misplaced my keys (or other things for that matter.) Guess I am just lucky in this regard.
Neil
Do a Google search on tracker transmitters. There's a bunch of cheap ones available and a bunch of circuits. They mostly seem to consist of a one transistor oscillator/transmitter operating in the FM band and a circuit with a couple transistors or a 555 timer to turn the oscillator on for a short duty cycle, like .2 second every 1 second. The low average duty cycle results in very low battery drain. You home in on it with a portable FM radio. Start with the antenna fully extended and shorten it as you get closer. A signal strength meter on the receiver would help. Orient the antenna around in different directions to help with locating. Homing is crude, but should get you to a room. With a 100mW oscillator/transmitter power level and a short antenna, it should give you at least a few hundred ft. range, maybe a lot farther..
The keyring beeper described by Neil sounds useful, but it would need to be put on the keyring BEFORE losing the keys.
Another thing, at a symphony concert the audience applause would turn it on and you'd be sitting there beeping during Ravel.
I'm really having fun with this
and, yup, it is Part 15.
I've got a 555 and some other
stuff sitting around here. I'll
see what I can do.
We had one of those things where
you clap your hands and the device
lets out a couple of beeps or whatever.
I don't know where it is - it would be
fun to experiment with.
The "wrong noise" is a problem. We
had
one of those "Clappers" to turn off the
TV in the bedroom at night. I would
sneeze and the TV would come back on.
Holst's "The Planets," especially "Mars"
would mess it up real good.
Bruce
Especially Mars.
Slope detection first:
So I put this ICOM IC-R2 handheld
scanner in to the AM mode and slope
detected the signal. Turns out I got
audio at 49.40. Makes sense. It's much
easier to home in on the transmitter this
way. AM receive instead of FM receive.
About Mars:
I guess this should be in the "Rocket Talk"
thread we had a while ago.
All these rockets on thie news.
Yesterday they launch tested that
new Orion capsule. An unmanned test
of a 4 man space capsule. Completely
successful test. NASA says it's for the
eventual manned MARS mission.
By the time we are really going to MARS
(20 or 30 years from now - it's a lot harder
than people think)
the technology will be completely different.
They are working on space hibernation - sort of
- I think. I don't want to use the phrase
"suspended animation." It remindes me too
much of "LOST IN SPACE."
Bruce