RF modules - Page 1
Forum section: electronics / beginners

author: gatoulisss
author_rank: Contributor
timestamp: March 07, 2015, 12:44:51 am
content: 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?http://www.ebay.com/itm/141196902303?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITand also can i control with the same controller 2 or 3 devices at 1000meter range?thank you!

author: Psi
author_rank: Super Contributor
timestamp: March 07, 2015, 02:38:53 am
content: You would need some better antennas to get 1km from those things.

author: gatoulisss
author_rank: Contributor
timestamp: March 07, 2015, 02:05:32 pm
content: can you give me an example of what i have to do?

author: tggzzz
author_rank: Super Contributor
timestamp: March 07, 2015, 03:50:12 pm
content: Quote from: gatoulisss on March 07, 2015, 02:05:32 pmFirst make sure you understand the legality of using different types or radio in your location. Get that wrong and you'll be visited by The Government.Next do some research and then you will be in a better position to say what you've done - and to ask more specific questions.Finally, come up with a specification, not a wish.It is unreasonable to expect people to spend their remaining life badly recapitulating stuff that is well described elsewhere.

author: gatoulisss
author_rank: Contributor
timestamp: March 08, 2015, 03:01:57 pm
content: im trying to found my country (greece) laws but i cant find them anywere, for sure the 433mhz are free licensed and also i have a remote here whitch is using 869mhz module so can i use it also?or what i have to do for 433 or 869 modules to reach 1km range in flatland?what you mean specification? i want to build an remote witch will have range about 1km in flatland and i would like if its possible some advise in how to do that

author: KM4FER
author_rank: Regular Contributor
timestamp: March 08, 2015, 07:39:19 pm
content: VK3YE ( search youtube for VK3YE ) has several videos on Experiments with low power UHF transmitters in which he performs some range tests which may be of interest to you.If you are looking for somebody to tell you to use product ABC then you probably aren't going to get that. Here's why.First, different receivers have different sensitivities. A really good receiver may be able to pick up a weaker signal than a cheap one and therefore give you greater range. Only way to know is to read the specs (assuming they are valid) and then test the receiver yourself.Transmitters may produce different levels of power which might affect the range. Again read the specs and test.The antennas used, both transmit and receive, will make a huge difference. An omnidirectional antenna will radiate the available power from the transmitter in all directions therefore the signal in any one direction will be weaker. A directional antenna will tend to focus the radiated power in one (or two) directions and therefore the signal could be greater at a distance but only in that direction.At the higher frequencies the RF may bounce around off of all sorts of objects including buildings, hills, walls, vehicles, towers and trees which could mess up the signal at the receiver.You are going to need to do some homework and read up on RF transmissions and propagation, study specs on available transmitter/receiver pairs, choose a product and then perform lots of testing.KM4FER

author: picandmix
author_rank: Frequent Contributor
timestamp: March 08, 2015, 08:20:01 pm
content: Are you intending to use them with an Arduino or similar micro ?Because the frequency is used my many other devices you have to use software encoding to ensure you send and receive the correct signals to / from the correct devices.If you want something with better transmission capabilities where the encoding is built in, then look at the XBee moduleshttps://www.sparkfun.com/pages/xbee_guide

author: gatoulisss
author_rank: Contributor
timestamp: March 09, 2015, 11:19:40 am
content: Quote from: picandmix on March 08, 2015, 08:20:01 pmyes i will work with pic microcontrollershttp://www.rfsolutions.co.uk/acatalog/FM_Long_Range_T7G___R7G_Modules.htmlsomething like this will be ok for what i want?

author: picandmix
author_rank: Frequent Contributor
timestamp: March 09, 2015, 12:23:14 pm
content: Quote from: gatoulisss on March 09, 2015, 11:19:40 amDon't know about those unit, though they seem expensive with each receiver and transmitter being separate modules.Are you wanting to do one or two way communication ?Have used these modules , though only for short range, but they indicate much greater distances up to 3km.Basically you just send /receive your data on the Pics usart line, the module does everything else for you; plenty of documentation on their site.http://shop.ciseco.co.uk/xrf-wireless-rf-radio-uart-serial-data-module-xbee-shaped/http://openmicros.org/index.php/articles/88-ciseco-product-documentation/238-1-getting-started-guide

author: wraper
author_rank: Unknown
timestamp: March 09, 2015, 01:16:37 pm
content: Take a look at LoRa modulation transceivers. They claim ultra high sensitivity and noise immunity at low baud rates and include Error Correction Code.http://www.hoperf.com/upload/rf/RFM95_96_97_98W.pdf

author: gatoulisss
author_rank: Contributor
timestamp: March 09, 2015, 04:15:49 pm
content: Quote from: picandmix on March 09, 2015, 12:23:14 pmi want 2 way communication, so how you achieve this distances?http://shop.ciseco.co.uk/xrf-wireless-rf-radio-uart-serial-data-module-xbee-shaped/with this module for example

author: picandmix
author_rank: Frequent Contributor
timestamp: March 09, 2015, 04:44:49 pm
content: Quote from: gatoulisss on March 09, 2015, 04:15:49 pmAs it says on that page -We have had reports of customers sending data over more than 3 KM using the standard supplied whip antennas out sideSeems they still supply the simple whip aerial as standard, though you can put on better.( the 'whip' they refer to is just that white piece of wire about 100mm long)http://openmicros.org/index.php/articles/84-xrf-basics/289-adding-antennas-to-ciseco-radiosUnless someone who has used these or any similar lo cost units and can say first hand they have proven them ok over 1km then you are going to have to try them for yourself.Having said that, Ciseco do say there customers report 3km so its down to believing them, in conjunction with your local transmission conditions ..? ( open farmland / countryside ? )I'm in a built up area so cannot do such distance tests.