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Jamez_Warner

Ground to Ground Long Range Video Link

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Currently building a large exploring tracked robot, and I'm just having a think as to how i'm going to get the onboard video back.

I need at least 10fps at a range of at least a mile in a vegetated area - is there any way this can be achieved ?

I have some 2.4ghz transmitters which have lots of airbourne range, but die after 30-40 meters on the ground :(

I'm guessing I may have to use a far lower frequency as that's affected less by obstacles - is there enough bandwidth on the UK PMR446 band ( walkie talkies )?

Here is the beginnings of the bot :

http://www.digital-car.co.uk/forum/viewtopic.php?t=467

Thanks for any help/guidance you guys can provide

James

Edited by Jamez_Warner

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I don't know where you are located, but in the USA the 434Mhz area is available for licensed ham radio ATV use. With a couple of watts, and good antennas, it should work decently.

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Why not get an aero pilot to fly a plane with a video repeater on board !!!!!!!!!!!!!!!!!!! :D:D:D

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If you could settle for 1 fps frame rate, you might be able to use a digital camera through a cellular phone or an RF modem. Otherwise try to setup a more sensitive receive station with a directional antenna.

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OK, I believe there is a area for ATV in the UK - i'll look into that....

I have a GPRS link for my internet ( 3-4kb/sec ) - that might be persuaded to transmit video, allthough it's prone to disconnections and network outages

Reckon with a decent patch antenna i'd manage a mile on 500mW / 1 Watt 2.4 Ghz ?

Also anyone know what sort of data rates you could push through an RS232 modem ? I could use walkie talkies to TX ( plenty of range )

James

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Reckon with a decent patch antenna i'd manage a mile on 500mW / 1 Watt 2.4 Ghz ?

Any vegetation that is in the LOS will absorb a lot of the microwave signal (blame the H2O). It is hard to say what your range will be.

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I know someone that has recently achieved 600m on the ground with a 10mW transmitter even in heavy fog. If I remember correctly he hasn't even changed the stock antennas. I must admit that I still don't understand how. It was clear LOS though.

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Most RS232 modems are only around 19.2K baud, but some of the better ones can do 232kb. It may be difficult to use walkie talkies, because you may need packet modems and a full-duplex radio for fast error correction of data, but I have been thinking of trying two pairs of walkie-talkies and streaming compressed images, since the high power RS232 modems can be expensive.

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In the air its 5 miles plus easily but on the ground it could be anything. All it would take is for your robot to drop down in a dip and the signal may even get cut off !

Terry

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considering the price I've bought a set to test B) - hopefully with a yagi/dish or maybe just the GPP on the RX I can achieve a good distance - will let you know how I get on... Thanks

james

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I look forward to hearing your results, it will be interesting !

Good Luck, Terry

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OK They arrived today, I thought what the heck lets give them a go with stock antenna's

So took a friend, a gps, a set of walkie talkies and a 7" TFT

Set out to do a line of sight test to begin with, used the GPS to measure distance and the walkie talkies to monitor signal quality. Signal dropped out at about 1.5km!!! It was a long walk back !

We also tested in a forest which gave almost 200m and one obscured by a hill - again around 200m

For £35, a true 1000mW TX, a colour night vision camera ( CMOS ), audio and an RX is an amazing deal - I recommend !

That range is almost acceptable with stock antenna's - Wonder what will be achieved with directional antenna.

James

PS. Are there any better antenna's I can use on the TX side? ( omni )

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I highly recommend double quad antenna for the receiver. It is easy to make and has good gain, which should tripple the distance.

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wow !! 4.5km clear sight !

Can you recommend any DIY plans that would work well ?

Also - the antenna on the RX is fixed, i'll obviously fit a connector - am I best sticking with SMA or something bigger/more sturdy ?

James

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ah good man - exactly what I was thinking of ! i'll drop him an email for some more details

James

HI,have you got the answer from him?

i want to build this system

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