Adding a filter to a cheap car stereo

So while my car is out for the count I am stuck driving a beast with no radio.  If you have ever driven long distances with NO radio then you know how mind numbingly boring it can be.  I managed to find the cheapest and most stripped-down radio for $25 at the local electronics store.  It wired up easily (given the 2 inches of old wiring that remained in the dash).  It also sounded alright given the 20+ year old speakers. That is until I fired up the engine and heard nothing but squeal from the speakers.  It also got worse as the engine RPMs climbed.  I managed to find a filter kit at a car store to fix just my issues.  It consisted of a giant inductor and capacitor thats meant to remove the alternator and ignition noise from the 12 volt power.  The capacitor was actually intended to be installed by the ignition coil but as it already has a new condenser it wasn’t needed so I installed it by the radio. The inductor was installed between the +12v constant hot and the radio +12.  The capacitor was installed after the inductor and grounded to the common ground.  To keep everything nice and tidy, I mounted the inductor to the back of the radio with the capacitor using one of the existing mounting screws.  My guess is that to keep the cost down they just left out all the  filtering components – and it shows.  After I installed this I no longer get the squeal that I had previously grown accustomed to.

Car stereo filter installed and mounted to the back of the radio

Car stereo filter installed and mounted to the back of the radio

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