Low cost Radio tranceiver Range :5Km Baud Rate : 19200-115200baud

I'm looking for "Low Cost" radio tranceiver with 5Km range and full-dublex
19200-115200 baud rate. Would you suggest one?

 

Could you tell us what you want it for?

If low cost is a prime consideration, you may be better off looking at half
duplex systems. If you don't especially want a serial port connection, you
may like to consider 2.4GHz Wireless LAN cards with a good antenna system.

Mark

 

What about the range of 5Km? Do you thik wireless LAN (802.11) would reach
that far?

 

Yes, but you have to have decent antennas. Have a look at
http://www.nodedb.com/australia/ or http://www.air-stream.org and see what
people are up to.

Mark

 

with the right rx/tx aerials you can expect considerably more , and
quite cheaply

 

A full duplex system requires two separate radio links, one for each
direction. To avoid the problem with duplex filters, use two complete
separate unidirectional radio links operating at different frequency
bands.

A 5 km range is easy, if you have a _guaranteed_ line of sight, but if
not, it becomes quite tricky to get a decent reliability, requiring a
lot of power (several watts), special modulation and coding systems to
avoid selective fading etc.

Then you have to consider in which countries this system should be
operated and check separately for each country which frequency bands
can be used for this kind of operation. Remember, you need two
separate bands, if you insist on full-duplex operation.

It would be easiest if some license exempt bands could be used, but
these are usually limited to 10-100 mW, which would not be sufficient
for reliable 5 km non-light of sight paths at those speeds. Also note
that there are usually a lot of all kinds of other activities on
license exempt bands that could block your link at much shorter
distances, thus, you may need some frequency hopping or spread
spectrum system to avoid the other users.

For reliable systems, most likely a licensed radio system would have
to be used, with type accepted devices and separate licenses for each
installed transmitter. Depending on your definition of "Low Cost" this
may or may not be acceptable .

Paul

 

On Tue, 13 Jul 2004 20:20:45 +1000, atec

While a WLAN link can be longer than 5 km, you need quite high towers
to have a clean line of sight path between the stations, with
preferably no obstacles within the first Fresnel zone .

In most countries the WLAN is limited to 100 mW ERP (+20 dBm) and when
the path loss for 5 km and 2450 MHz is 114 dB, the received power with
an omnidirectional antenna would be -94 dBm. After the feeder losses
at the receiving end the power level entering the WLAN card can be
calculated. Compare this figure to the nominal sensitivity of the WLAN
card at various speeds and you know how much receiver antenna gain you
are going to need. This calculation assumes a clean path with
unobstructed Fresnel zone.

You must also consider the local noise level near the receiver from
other sources.

Paul

 

One of the unit in my implementation will be mobile and therefore wireless
LAN seems to be out of question (no tower, no directional antenna). Any
other recommendation?

 

COuld you define "low cost"? - it such a relative term.

Mark

 

< US$300

 

Have a look at this unit. It is US$269. It will have the same problems as
the Wireless LAN as it operates in the 2.4GHz band as well.
http://www.microdaq.com/wireless/aerocomm/index.php

If this is for import to Australia, you will need to add freight and GST
(depending on application). You may get a tax reduction as an export from
the country of origin.

If you are looking for a unit with a that will handle 5km all terrain, you
will need to up your budget. Using something outside of bands like the
2.4GHZ band, you may require a licence which will add to your costs.

 

GSM? Cellular technology is cheap enough these days.

 

GSM device itself is not expensive but call charges are not.

 

Try wifi with a decent antenna.

A modified satellite dish gives 29dBi which will easily do 5 km, but an
omnidirectional waveguide may work too.
http://members.iinet.net.au/~clark/FreeNet/Satenna/

Approximate wifi distances for various antenna types are at the bottom of
this page:
http://members.iinet.net.au/~clark/FreeNet/antennas.htm



gtoomey
www.ausinvestor.info  Australian Investor Forum

 

GPRS, then?
< $200 US. Call charges negligible for smallish amounts of data in
Australia.

Alf.

 

Completely unrealistic with those requirements.

Drop the full duplex and data requirements and provide at least nearly
line of sight paths (with the other station up in a high tower or
balloon) may make the situation more realistic.

Paul

 

Hmm, sounds like an EER application to me.

 

In the Netherlands you can get a rate of Eur 1.5 / megabyte for GPRS.
For sending and receiving, so for GSM-to-GSM cost you have to double it.
But if the amount of data is limited this is very acceptable.


Thomas

 

The good thing with the original 1200 bps half duplex audio FSK system
is that it works with practically any unmodified radio telephone with
a microphone and headphone connector, thus simplifying any type
acceptance issues.

The 27 MHz Citizens Band might be an alternative to reach the 5 km
distance, provided that data transmission is allowed on the CB
frequencies in a particular country. Of course, the 1k2 half duplex
throughput is "slightly" below the 19k2.. 115k2 full duplex throughput
expected .

Paul

 

With that kind of size, it's difficult to fit into a model plane...

Kelvin