Cytron Technical Forum

by **azlin** » Mon Mar 21, 2011 10:48 am

hi,
i want to ask if the receiver at 6m or more far from transmitter ,i want the receiver not to response, even it receive signal from transmitter. It is possible to do that?

by **ABSF** » Mon Mar 21, 2011 2:31 pm

how does your receiver tell that the Transmitter is 6m away? If you Rx is smart enough to tell you the distant, of course it can be done.

Allen

by **azlin** » Mon Mar 21, 2011 5:11 pm

in my circuit, there is 1 antenna in each RF Tx modules and Rx...
does the length of the antenna effect the distance between Tx and RX?

what if i make really short antenna?how does it effect for the circuit..

by **azlin** » Mon Mar 21, 2011 7:38 pm

hi..
what i means is in my project is using this RF modules...
the freq is 315MHz..when i test the distance between Tx and Rx,the distance is more than 10m...its quite long range...
my objective is the max distance between Tx and Rx is in 5m so the buzzer that placed at Rx will make sound..and if the range is more than 5m the buzzer will stop make a sound..
so i want the distance in a short range..so,is the component suitable for my project or not?
if not,any suggestion that can replaced the RF modules?
i use this RF modules together with HT12-E and HT12-D...
can u pliz answer...
tq..=)

by **ABSF** » Mon Mar 21, 2011 8:50 pm

azlin WROTE:hi..
what i means is in my project is using this RF modules...
the freq is 315MHz..when i test the distance between Tx and Rx,the distance is more than 10m...its quite long range...
my objective is the max distance between Tx and Rx is in 5m so the buzzer that placed at Rx will make sound..and if the range is more than 5m the buzzer will stop make a sound..
so i want the distance in a short range..so,is the component suitable for my project or not?
if not,any suggestion that can replaced the RF modules?
i use this RF modules together with HT12-E and HT12-D...
can u pliz answer...
tq..=)

I think nobody will use the "Carrier" Tx power or the Rx receiver sensitivity to determine the distance of transmission. Because the media of transmission (air) plays an important part in the transmission. Your Tx and Rx module may be able to go 10m in free air but if blocked by a concrete wall, it may become 3m or 4m. Another factor is the antenna, antenna can be directional or non-directional. The directional antenna can have high gain and can go further the distance. So you see, using the above method is not a good way to determine the distance between Tx and Rx.

Read the discussion here and get some idea of distance of transmission vs Tx power

http://www.edaboard.com/thread31800.html

Allen

by **azlin** » Mon Mar 21, 2011 9:25 pm

ok2...tq very2 much for your advice n suggestion..=)

by **yonghui** » Wed Mar 23, 2011 9:59 am

hi,

i think there is some simple circuit that detect the strength of RF, see it before somewhere.

regards,
yh

by **ABSF** » Wed Mar 23, 2011 1:46 pm

yonghui WROTE:hi,

i think there is some simple circuit that detect the strength of RF, see it before somewhere.

regards,
yh

Something like this?

http://www.seekic.com/forum/22_circuit_ ... METER.html

Allen

by **yonghui** » Thu Mar 24, 2011 10:50 pm

hi,
im not so sure how good is these signal strength measurement, but its simple,
someone can just try to modify and connect it and read it using ADC of PIC to get the signal strength.
http://www.zen22142.zen.co.uk/Circuits/rf/sfsm.htm
http://freecircuitdiagram.com/2009/02/02/another-rf-field-strength-meter/

regards,
yh

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