Remote meteorological stations have used these, but you need quite a lot of effective radiated power. Since directional antennas could not be used, quite a lot of transmitter power would be required.
A solar storm can severely disturb the ionosphere and hence take out the communication for days.
Also thunderstorms can create quite high noise levels at the low-HF frequencies.
In this case the antenna would have to be much smaller than the wavelength and hence the antenna efficiency would be as low as 1 %, requiring a considerable amount of transmitter (and hence main AC) power.
I can only post from google groups, tack this into the discussion for me, would you?
Steve Roberts.
I posted this, but I doubt I get past his spam traps.
Quoting myself:
Look, there are older services in use out in the boonies, its just finding them. I know there are allocations from my ham radio days.
There are 30, 49, 72,75 and 900 mhz distributed systems for this sort of thing.
many government folks use meteor scatter, no kidding.
Are your units within a RF hop of each other or randomly distributed?
If within a hop, you can use packet protocols, ie forward and store,
1200 or 9600 baud ham radio style packet works quite well on the business band and there are HF packet protocols as well..
There were/are 138/142 Mhz low data rate satellite services , 220 mhz land mobile radio data services, and vehicle/cargo tracking.
Near Vertical Incident Skywave comes to mind as well and there are HF utility band assignments for this sort of thing. Heck, NVIS messaging would be a startup I would invest in.
Pipeline and Power companies need these services, and there are pipeline and power companies everywhere in the US Get a ride on some one else's low band or 900 mhz scada systems....
Your looking in the wrong place with cellular.... There are FCC allocations for this sort of telemetry. I would think inmarsat or a KU band uplink is too expensive for you, but there are other services for trucking, etc.
Try Orbcomm for example. There must be other little LEOs.
These things were around 700$ a few years ago:
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And I would not doubt one bit that iridium offers a similar service.
Take a look at the FCC regs, pick a candidate service and then go to the FCC GIS and search for licensee within radius of a coordinate.
please note my address on this post is a spam trap.
This is what makes cell so attractive. The installed base is very large so that a change in frequencies or protocol will be very slow or will not happen at all.
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Regards, Joerg
http://www.analogconsultants.com/
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The locations of cell sites are not publicly available. They used to be, many years ago, when each site was FCC licensed on a latitude/longitude basis. So, a lot of that information is dated and inaccurate by now.
There are companies that do drive testing for the carriers for competitive / network quality concerns. Telephia is one such company if memory serves. They drive around in trucks making automated calls with specialized "handsets". Usually the carrier provides the handset, so they can track/collect data on their end as well as the mobile drive unit.
But I'm sure that data's expensive, and there are probably many hoops to go through to get it, along with confidentiality agreements, etc... So, forget that approach for most casual users.
Another option is to look at public (and some private) tower companies. American Tower, SBA, Crown Castle, GTP, etc... If they have their tower inventories in the clear (most do, even if with registration requirements), you can pretty much guess the smaller towers hold cellular/PCS (as opposed to taller legacy paging / broadcast type sites). Ditto for rooftops.
Of course, that won't tell you whose on them (which carrier), but major metro centers are cloud-covered with signal anyway.
I mention the public tower companies because unless the tower is close to an airport (and a few other restrictions), there no requirement to register the tower with FCC (FAA - long story). All of which means shorter towers; those likely to hold PCS and Cellular, are not available in public databases at FCC either.
I wouldn't give you a nickle for the entire Google tower site database.
At a first cut you might wish to consider General Packet Radio Service (GPRS) modems. The operating cost is based on data volume rather than pure monthly. Otherwise, you may wish to look at what can be done with ISM bands.
They do roll over. By now I have a bazillion minutes. I don't think there is any cheaper way to have a cell phone and always keep the same cell number. All those other deals I looked at required prepaid cards that would expire in rather short time frames, between one and three months.
I pay around five bucks a month. That's it.
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Regards, Joerg
http://www.analogconsultants.com/
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That would mean our own RF links. It's what we are doing right now and it requires a link through local premises. However, the goal is to have the units send their data straight to a headquarters or a service location.
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Regards, Joerg
http://www.analogconsultants.com/
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Same as the cell phone services and maybe a few small players piggybacking / reselling bandwidth on the main nets.
bands.
location.
That could be difficult with ISM without running concentrators. Still limited by line of sight. GPRS is nearly global in coverage, the modems seem to be about US$ 1000 each or less.
Ok, yeah, we were planning on contacting those first. According to one poster in this thread Verizon seems to be the prevalent carrier down there.
How can GPRS be global if it uses a cell network? Cell networks have plenty of holes in their coverage. But anyhow, $1000 modem cost is outrageous, that would blow the method straight out of the water. It needs to be well under $50, which GSM and CDMA would be.
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Regards, Joerg
http://www.analogconsultants.com/
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Global in the sense that GPRS is available anywhere GSM cell service is available. Thus it would include Moscow, Kampala, Beijing, Canberra, Marseille, etc.
Quote: "Amounts deposited into your account expire as follows: cards less than $25, 30 days; cards $25 to $75, 90 days; $100 cards, 365 days. Unused account balance is forfeited upon expiration."
IMHO that is not a good deal at all. Sorry, but there I've got the better deal, much better (with VirginMobile).
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Regards, Joerg
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But leaves out much of America. A neighbor fell for the GSM deal, signed on the dotted line, for two years. That was before the 30-day cool-off was signed into law. Had to put a yagi on the roof and his cell phone was, ahem, not quite wireless anymore.
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Regards, Joerg
http://www.analogconsultants.com/
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No, didn't need that function yet. But the phones aren't that different from the ones used for regular (expensive) service. Nowadays a true serial link is unusual, it all goes towards USB.
For mine, this way:
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--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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