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RF receiver loss of range

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afbecker

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First let me say this web site is an outstanding resource.

I am building a remote shutter device for my beloved old SLR camera since unlike the new electronic ones it doesn not have a built in one.

At the heart is a PIC16F84 which handles logic and motor control. A battery powered geared down motor activates the cable release. The range of motion is limited by feedback from reed switches and a magnet at each end of the plunger travel The reed switches report to the 16F84 and tell it when to stop and reverse, etc. The PIC is clocked via a resistor/capacitor connection to the OSC pin as prescribed by the manufacturer. The nominal clock rate is 4Mhz. The PIC runs at 5VDC provided by a 9V battery and a 7805.

To trigger the process remotely I have canibalized a toy car for a very cheap ($6.00) transmitter/receiver pair at 27Mhz. The receiver runs at 3VDC provided by the 9V battery and an adjustable regulator. The idea is that the receiver output (at 3VDC) will be detected by the PIC on an input pin and start the motor control sequence.

The receiver operating on an independent power supply gives me a strong 3V output of 3VDC from a range of about 30 feet or more, but the minute I connect it to the controller circuit and the 9V battery with the 3V regulator, the range drops to about 4 feet!

I speculate that there may be a great deal of noise created by the PIC oscillator circuit either on the ground bus or even the positive line which the receiver doesn't like. I wonder if some sort of filtering is called for.

I very limited in my understanding of RF circuits and their pecularities and would appreciate some help on this project.
 
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