EMI prevention / protection?

dave.harper · 2009-10-30T14:43:24+00:00

I'm using a wein bridge oscillator as an audio tone generator in aradio modem (~2kHz). Ironically, when the transmitter is turned on,RF from the transmitter (~144MHz) causes the oscillations to diepretty quickly (a fraction of a second). If I hold the transmitterfurther away, it continues oscillating, but I'd prefer to reduce theEMI to have a more robust design.I have a few questions I was hoping some people with EMI experiencemight be able to shed light on:1. Is the EMI likely cause by voltage fluctuation in the supplyvoltage, or the input lines to the op amp? Or maybe in the IC itself?I have a .01uF decoupling cap on the supply voltage (was out of 1uFcaps), but maybe this cap needs to be larger?2. Would a low-pass filter on any of the op amp inputs be a goodoption, or would shielding be a better option?3. If I used shielding, would standard aluminum foil be adequate?What general guidelines are there regarding form and allowable holesin shielded enclosures?Thanks in advance!Dave