Long range, low bitrate, small data transceiver unit for telemetry data

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Is there long range (10-100km), low bitrate (1200-19200 baud), small,
baterry operated radio transceiver units to send/receive digital data to be
used on a telemetry application?




Re: Long range, low bitrate, small data transceiver unit for telemetry data



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Satellite phones :-)


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Jenal Communications
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Re: Long range, low bitrate, small data transceiver unit for telemetry data


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Actually, that raises an interesting question - I know various
applications including buoys, wild animal research collars, etc. use a
satellite uplink to communicate GPS data and other telemetry to home
base.

Who does one contact about buying bytes on a bird like this? I'd be
interested to find out what it costs to set up this sort of thing.


Re: Long range, low bitrate, small data transceiver unit for telemetry data


snipped-for-privacy@larwe.com says...
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http://www.argosinc.com /

A general search on argos satellite applications will yield lots of
results.


Mark Borgerson

Re: Long range, low bitrate, small data transceiver unit for telemetry data


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EXTREMELY interesting, thanks for the link! One transmission a day on a
floating platform is about $77 per month, which gives you position data
plus 256 bits of telemetry.

There is a clause in there about not being able to get bird time if
there is a commercial equivalent to Argos, though. I wonder what
commercial equivalents there are... hmm, more research necessary.


Re: Long range, low bitrate, small data transceiver unit for telemetry data




snipped-for-privacy@larwe.com wrote:
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Another low bitrate satellite service that is available worldwide is
Inmarsat D+.  This provides bi-directional communication to small
mobile terminals most places more that 5 degrees away from the poles.
The smallest terminal available is the SAT-201 which is around 4.5
inches in diameter and 2 inches tall.  More info from
http://www.satamatics.com

Ian


Re: Long range, low bitrate, small data transceiver unit for telemetry data


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Thank you for the link and information.
It is very intereting.
On their brochures
(http://support.satamatics.com/doc/portal/dl/bro0018/-/en/pdf/bro0018.pdf )
they say data transmission rate from terminal to satellite is ~10bits per
second and receive bitrate is 9 bits per second. They also say "By pressing
a panic button, the message transmission frequency can be dramatically
increased - for example, to every few minutes, to provide Search and Rescue
authorities with rapidly updating position reports." which is very good for
the applications given in their web site.

I'm afraid our applications requires almost continious communication between
ground station and balloon at 1200-19200 baud and that's why Satamatics's
terminals would not be appropriate for our application. But it is good for
me to learn the existance of such an alternatives. Thank you.

How they charge their services? Does cost defined by the amount of data
communicated ? Do you know how much it cost?

Thank you

Leo



Re: Long range, low bitrate, small data transceiver unit for telemetry data



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Thanks - Magnus pointed me to Skywave's Inmarsat-D+ products, and that
kind of opened the funnel for me, I've been looking at all sorts of
options. They basically fall into three categories:

* Argos - restricted use (my application is probably eligible), 256
bits uplink only, low power requirements.

* Inmarsat D+ SMS - bidirectional telemetry and command information. It
would also be possible to use a prepaid [voice] satphone's SMS
capabilities to do the same thing, possibly cheaper (Skywave hasn't
returned my emails asking for pricing info).

* Other satellite data services (R-BGAN, Inmarsat mini-C, etc etc).
Would allow full uplink of image data as well as low-bandwidth
telemetry. I would never need to recover the vehicle if it had this fat
a satellite pipe.

The eye-opener for me is that all this stuff is really COTS and really
cheap (compared to what I thought it would cost, anyway); it looks as
if <$4k of equipment and as little as $0.79 per minute could get me a
full "high-bandwidth" bidirectional satcom system.


Re: Long range, low bitrate, small data transceiver unit for telemetry data


Thank you very much for the "Argos" link.
I have found it very interesting. Following link from the Argos' web site
provides a list of transmitter manufacturer for the Argos system
http://www.argosinc.com/documents/list_manufs.doc

My intented implementation in the original posting/question is a
semi-controlled baloon. Because of the very limited weight carrying
capability of the baloon, we can not carry big, high power transceivers.
Transmitters for the Argos' system could be very small (as light weight as
7gram t be carried on a bird http://www.argosinc.com/documents/sysdesc.pdf )
. But because our implementation requires two way communication and we do
not have the oportunity to wait the next pass of the Argos' satellites over
Australia, unfortunatelly Argos system does not seems to be applicable in
our case.

So I'm still looking for
    *  Long range (10-100km)
    *  Low bitrate (1200-19200 baud)
    * Small
    * Battery operated
    * radio transceiver units to send/receive digital data to be used
between a semi-controlled baloon and a ground station for telemetry and
control application.




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Re: Long range, low bitrate, small data transceiver unit for telemetry data




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Why didn't you say that in the first place ?

It makes *ALL* the difference if the stations are down in the ground
clutter of if you have a free line-of-sight path.

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So apparently you only have the weight restrictions on the balloon
system, not on the ground system?

Do you have power restrictions on the ground system ?

Could you use directional tracking antennas on the ground ?

With such applications, I would suggest that you stay away from the
license free bands and get a dedicated frequency (pair) with a
sufficient power limit (say 1-100 W) for the ground transmitter from
your telecom authorities.

For the control functions, you might even consider systems intended
for model aircraft control and use a completely separate system for
telemetry downlink on a different frequency band and thus be able to
continuously communicate in both directions. You might even set up
multiple telemetry receiving stations on the ground at different
locations.

Paul
 

Re: Long range, low bitrate, small data transceiver unit for telemetry data



"Paul Keinanen"
 "Leo Patrick"
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**  Don't get too excited just yet  -  there are still heaps of important
details the OP has not revealed about his app.


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**  At 100 km range, that damn balloon better be up in the stratosphere for
a free line of sight !


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**  With a Tx weighing in at circa 7 gm all up  @ 100 km range plus hovering
barely on the horizon, the OP will need access to the Parkes radio telescope
dish !


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**  Needs plenty of watts on the up link plus massive gain with a tracking
dish for the down link.



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 **  Or just get NASA to help out.

 They could help the OP with his spelling too.




...........   Phil





Re: Long range, low bitrate, small data transceiver unit for telemetry data


On Tue, 12 Jul 2005 16:35:19 +1000, "Phil Allison"


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Theoretically, you only need to be at 625 m altitude to get the 100 km
radio horizon, in which the attenuation is only slightly larger than
direct line of sight. From a plane flying at 10 km, the whole island
of Cyprus (about 150 km long) fits nicely into a singe view.

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A 100 km troposcatter path not very hard with directional antennas and
moderate transmitter power.

Paul
  

Re: Long range, low bitrate, small data transceiver unit for telemetry data



"Paul Keinanen"
 "Phil Allison"
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**  Over water that is about the *visible* horizon from 625m  -  providing
there are no waves at all.

BUT for a CLEAR line of sight over terrain that may include ground levels
thousands of  feet above sea level -  my comment stands.


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**  That 100 km diameter mill pond is damn hard to find.


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**  10 km altitude  IS  in the stratosphere, depending on one's latitude.

The OP  likely wants his 100 km range to extend right down to local ground
level -  to maintain remote control.



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 **  How lovely and vague.

   And useless and smartarse.



.............    Phil
 



Re: Long range, low bitrate, small data transceiver unit for telemetry data


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Anyone would be forgiven for thinking you have a
monopoly on RF technology. You get nasty when Paul
confronts your good story with actual facts based
on such wishy washy crap like geometry and real
world observations. Sounds like you want him to go
away and stop undermining your "AWW-thorra-TAY".


kind regards
Mark

Re: Long range, low bitrate, small data transceiver unit for telemetry data


On Tue, 12 Jul 2005 17:24:48 +1000, "Phil Allison"

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Just in case someone might be more interested in technical details
than in the mud slinging contest, here are some details.

Troposcatter links have been used for decades in areas with no
infrastructure to carry telephone circuits prior to Inmarsat satellite
phones.

For instance between the North Sea oil rigs and main land
England/Scotland. On the land side huge fixed reflectors were erected,
but still quite high transmitter (kilowatts) power was required. There
was even a fear that the high field strength at the oil rig might
create some sparks and ignite the oil/gas vapour floating around.

The idea with a troposcatter link is that both stations should see the
same air mass in the lower troposphere (1-2 km) and when the
transmitted signal hits that air volume, it will scatter somewhat and
part of it will scatter towards the receiving station.

This is a similar situation as the afterglow after sunset, when the
western sky (on both hemispheres) is still bright, while the sun is
below the horizon. The sky is brightest around the area where the sun
just set, i.e. the scattering is strongest in directions close to the
ray direction.

The situation in troposcatter is similar, the larger the scatter
angle, the weaker the signal will be. The longer the troposcatter
link, the higher the commonly visible air volume must be (and thus the
air is less thick) and also the scattering angle becomes large, thus
hugely increasing the attenuation.

For a 100 km line of sight path (e.g. between two balloons), the path
loss will be about 120 dB. A 100 mW (+20 dBm) transmitter and a
receiver with -120 dBm sensitivity should be easily be able to
communicate with a 20 dB margin. However, on a license free band, all
devices that are within the radio horizon of the receiver would appear
as interference, most likely interrupting the communication.

However, if we want to build a ground to ground troposcatter link at
100 km, in addition to the 120 dB free space loss, you would have to
add about 50 dB (100000 times more power) for the troposcatter losses
at this distance for maybe 50 % of the time. Thus, a few wats with a
small yagi at both ends should do the trick.    

However, the troposcatter link is notorious for fading, so if you need
a higher reliability, the transmitter power needs to be increased. To
get from 50 to 90% reliability of the time, the transmitter power
would have to be increased 10 times (10 dB). Also stepping up to 99%
would add an other 10 dB as would going to 99.9 %. Even the Perks dish
with a huge transmitter would not be able to provide 100 %
reliability, since maybe during an hour each year the signal would
simply escape into space due to the air refractive index.

All the previous calculations have assumed that there is a free view
to the horizon. However, if there are some local mountains, you would
have to beam your signal higher to get above the mountains and hit a
common air volume above them. The higher in the air the scattering
volume is, the larger deflection is required and the losses will
increase.

As a rule of thumb, for every degree you have to increase the antenna
elevation to get past the mountain, the troposcatter attenuation will
increase by 10 dB, i.e. the transmitter power should be increased 10
times.

VHF/UHF/microwave communication is certainly possible behind the
horizon,  but to get a reliable link, you might end up at power levels
that are hazardous to your health.
-------------
One other interesting observation of wireless products advertised by
various vendors is that in order to get the distances claimed, the
station would have to be in orbiting satellites, preferably on the far
side of the Moon :-), to avoid the noise and interference from other
stations in the same frequency band.  

Paul
  

Re: Long range, low bitrate, small data transceiver unit for telemetry data


Paul,

Thank you for your very informative posting.
I've read with greath appriciation.
Regards,

Leo Patrick

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Re: Long range, low bitrate, small data transceiver unit for telemetry data



"Leo Patrick"
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** Is there the slightest chance YOU are going to explain what your
requirements are in sufficient detail  ??

   Or are you just another stinking troll  ??


   BTW   Get a bloody spell checker !!




..........   Phil






Re: Long range, low bitrate, small data transceiver unit for telemetry data


Leo,

What is your application?  I have launched weather balloons a couple of
times for the purpose of  photographing the curvature of the earth at very
high altitude. I used a mobile phone on one and radio beacon on another. A
future launch will occur in a month or so with a similar setup.

You can read about my failures and successes here:
http://members.optusnet.com.au/~philpawlowski/index.htm

My email address is at the bottom of the balloon launch 2 page if you wish
to contact me. There are some issues that have to be overcome. Some of which
you may know and others you may not. Here are a few:

1. Modern GPS units only report to 18km altitude. Balloons can go over 30km
alt
2. Mobile phones don't work above a couple of hundred metres. If you want to
use one, its purpose will be limited to letting you know where the payload
is only after it has landed on the ground assuming it lands in a mobile
phone coverage area.
3. Air currents can be strong. My last balloon ended up almost in NSW. I
launched it only 10km north of melbourne CBD. Its flight time was only
around 3 hrs.
4. Flight time can be calculated rather accurately. Its a function of the
balloon size, and how much gas you put into it. So at least you will know
when your balloon will pop and descend.

There are of course many more issues including air safety etc etc.... With
regard to your specific question of data transfer, there are a number of
options. On my last balloon I had a 1mW beacon courtesy of the local beacon
finding club. It weighed about 15 grams excluding battery. It was powered by
a D size lithium cell. This would have lasted at least 2 weeks continuous TX
and contributed to most of the % of weight of the payload. It worked very
well. Anything at that altitude will work very well for hundreds of km.

For a bit of nostalgia, I will be choosing the hellschreiber (google)
technique to transmit data back to the tracking vehicle next time but of
course there are much more complex systems you can go for. The Tiny Trak may
be just what you are after if you are after a cheap and easy more or less
off the shelf approach.

Regards,
Phil


"Leo Patrick" <lp> wrote in message
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Re: Long range, low bitrate, small data transceiver unit for telemetry data




    Sounds like a cool experiment, there used to be a
CAA regulation ages ago about banning photos within a certain
angle of vertical, I'm not sure what the reason was but it
may pay to check if it still exists.


Regards
Mark Harriss

Re: Long range, low bitrate, small data transceiver unit for telemetry data


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In a similar vein to hat Phil (not Allison) wrote, from the few
high-altitude balloon things I've seen on the net, it seems more common to
rely on data-logging based on the idea that you can locate the balloon when
it returns to earth.




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