Electronics

truptesh · Joined: 02 Aug 2008 Posts: 3 Location: mysore

Can anyone please suggest a method to reduce noise in an RF receiver.....[/b]

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truptesh Wink

neon · Joined: 25 Feb 2006 Posts: 598

It is kind of hard to give advice since we have no idea of the noise spectrum. But usualy most of the noise is present at the input and amplified as signalL.Are you sure that there is no sporadic oscillation? some noise can come from the power suplly expecialy a PWM then again it would be consistence. is the signal being fed by a coax cable and is the shield tied at the source only. shield to be effective must carry no current is just there to shield EMF. another good source is ground loops that is usualy associated with daisy chain the ground. best you can try is isolate the source gnd the input and see what you get that way.

truptesh · Joined: 02 Aug 2008 Posts: 3 Location: mysore

lemme explain a bit....... then maybe you can suggest me something.......

we are designing a remote control using RF transmitter and receiver(433 MHz) to drive a load... say like a motor...... we generate a square wave from a 555 timer and transmit it........ at d receiving end we provide it to a JK flipflop........ but the receiver shows d presence of some noise and unfortunately without transmitting any signal, the noise itself toggles the flip flop......... the noise is more or less a square wave.....of about 4V (p-p)..... and contains frequencies from 1 Khz to 5 Khz......

we actually tried a LC filter... but it isnt working........

so.... now you may be able to suggest me some way..........

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neon · Joined: 25 Feb 2006 Posts: 598

transmit 433mhz out of an LM555 that is a nice trick. considering that the tr/tf is 100ns. now here come my question do you realyu know what you are doing?. i quaranty you that you are not transmitting at 433mhz more likely 50mhz MAX carbage. Just wish for things to hapen does not make it so. maybe you can provide some schematics for us to look at. because i say INPOSSIBLE.

truptesh · Joined: 02 Aug 2008 Posts: 3 Location: mysore

by saying 433 MHz i mean the device specification...............

anyway have a look at the device i'm using..........

http://www.sunrom.com/index.php?main_page=product_info&products_id=117 (receiver)

http://www.sunrom.com/index.php?main_page=product_info&products_id=116 (transmitter)

these are exactly the components we have got........
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truptesh Wink

neon · Joined: 25 Feb 2006 Posts: 598

I believe there is a big interface problem. the transmitter probably cannot handle the signal at the input and saturates and what you get is the components of all those delays and settling time . a square wave has two stable condition on-off. try using pin 7 as an output that is a sawtooth. or make the square wave is a sinusoidal input by adding caps or an active filter.the whole schematic application will help a lot. bits and pieces leads to missconception.

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