RF modules

[gatoulisss]

hello im very new on the rf systems and i would like advise.
i want to make a control with range 1000meters how is that posible? would something like this work? https://www.ebay.com/itm/141196902303?_trksid=p2060778.m2749.l2649&ssPageName=STRK:MEBIDX:IT
and also can i control with the same controller 2 or 3 devices at 1000meter range?

thank you!

 

[Tony Stewart]

Without doing a path loss design with suitable antenna, I would expect 30m distance minimum and more with great effort on antenna.

1km is a pipe dream.

 

[gatoulisss]

so what i have to do for the range im interesting in?

 

[MikeMl]

so what i have to do for the range im interesting in?

No way to do it using license-free ISM bands. That kind of range requires radio license paid to government, and expensive equipment.

 

[JimB]

Having a look around on the interwebs, I found a specification for the modules which you listed.
Transmitter power is 25mW (+14dBm)
Receiver sensitivity is -105dBm

Assuming a completely clear free space path between transmitter and receiver, the path loss would be 85dB.
Using simple dipole antennas at each end of the link the signal power at the receiver would be +14 - 85 = =-91dBm

So the received signal exceeds the receiver sensitivity by -91 - (- 105) = +14dB

The link will work, but ONLY if there is a clear line of site path between transmitter and reciever.
In an urban environment with building between the Tx and Rx, it will not work.

Depending on what you are really trying to do, you need a proper licenced radio system.

JimB

 

[Nigel Goodwin]

Not at all, unlicensed systems are available - although it may well depend on the unmentioned location of the OP.

https://www.rfsolutions.co.uk/acatalog/Remote_Control_Systems.html

Up to 4000m is listed on there.

 

[MikeMl]

Not at all, unlicensed systems are available - although it may well depend on the unmentioned location of the OP.

https://www.rfsolutions.co.uk/acatalog/Remote_Control_Systems.html

Up to 4000m is listed on there.

Not legal in the US; not exactly cheap, either. OP started trying to do it on the super cheap...

 

[JimB]

Looking at the specifications of one of the modules linked to by Nigel:
Tx power is stated as +20dBm
Rx sensitivity
Frequency 868MHz

Running the same calculations as for the previous 434MHz modules, the fade margin is +20dB.
Which means that they would work very well over a 1km clear path.

JimB

 

[gatoulisss]

so what equipment i should use and how i can achive this range? size matters so i want something as small as possible... whith this system i want to control a pic for example

 

[Tony Stewart]

so what equipment i should use and how i can achive this range? size matters so i want something as small as possible... whith this system i want to control a pic for example

Without defining your environment ( altitude variation, proximity to buildings , trees, ambient noise levels) your data rate, your desired error rate, and much more
this is a pipe dream.

Anyone who asks such a request is naive to the effects of path loss vs frequency , antenna effects, signal reflection, Rice fading and many other challenges.

As it stands your question is grossly flawed.

try a CB radio

 

[ronsimpson]

XBee come in high power and low power.
There are several different frequency versions. The 900 mhz versions have longer range. But they can not be used on most countries. There is a 868mhz version.
Not low cost. Not small.

Do you understand "Line of sight". Put your eye at the transmitter and you must be able to see the receiver. No mountains, buildings, trees. I want you to understand "line of sight".

Do not use 2.4ghz out side. I do this but I live in a very dry place. If the humidity is high then I loose communication. (rain and fog kills the signal)

 

[gatoulisss]

the country i want to use it is greece the environment is flatland with sometimes rain there are no buildings between this range there are 1-2 trees only... the data i want to send is mostly on-off or some sounds for example.. as i tell im very new in RF so i dont know much to tell about it i tell just what i would like to do.

thank you for helping me!

 

[b.james]

Notice they say dipole antenna either end . Well thats the least you can do
I have two modules transmitter and receiver at 3 kilometer direct line of site with a two element yagi antenna at both ends
Not hard to make 3 pieces of wire in a H pattern with all but 1 half element grounded to shield and the driven element fed by center line through a 100 microFarad cap. You need to learn a bit though and I am not going to go out and measure the bits for you so don't ask. Research it yourself . Mine is a water tank sender on top of a hill for cattle . needs lots of servicing as its all out in the weather

Here are the modules I used from Oatley Electronics and 12 V . Sparkfun has similar
https://secure.oatleyelectronics.com//product_info.php?cPath=47&products_id=384

but I see they are now 5V not 12 and that makes a big difference.The transmitters are still 12 Volts and touted as 1.5 km with this module https://secure.oatleyelectronics.com//product_info.php?products_id=747
https://secure.oatleyelectronics.com//product_info.php?products_id=747

**broken link removed**