Voltage Regulator supplied with the Jabiru 3300 engine.

I thought I would set up my voltage regulator on the bench and see how much RF and power line interference it causes.

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I connected it up to a 12v lead acid battery and supplied it with 24v AC, It's as I suspected a simple SCR switching regulator that pulses the battery to maintain a set average voltage in this case 14.5 v.

It charges the battery at 14.5v (Cold) as you can see, and if I remove the AC input the battery voltages drops as per normal. Also the little red LED comes on to warn you we are not charging. If this happens in the air I don't see as a major problem , In my case would only be drawing a few amps so with a well charged battery would last many hours and will not effect the ignition.

The traces are voltages developed across a .5 ohm resistor in the main line from the regulator. So what you are seeing is current pulses going into the battery.

The single blip is when the battery is fully charged with no load, and the other is a lesser charged battery with some load.

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Here are some shots of the battery voltage on charge. There is 150mv plus of ripple on top of the 14.4v, you can hear it in the radio , not loud but it's there , so I will be installing filters, one on the charge side to smooth the charging pulses and one on the load side for the more sensitive equipment. For the charge side I have chosen a 10,000uf 100v Low ESR capacitor by RIFA PEH-200 series and on the AV bus I have connected a 10,000uf 25v capacitor , just an ordinary PCB mount type nothing special here.When I installed the 10,000uf 100v capacitor I put it under the seat in the right side. I did this for 2 reasons. First because it has to handle large currents it is important to keep it in a cool place. Secondly the cable running from the regulator to the capacitor will have resistance which will slightly reduce the charging current and likewise the return cable will tend to reduce the discharge current this also helps to keep the capacitor cooler.

NOTE If your battery ever went open circuit and you don't have a capacitor between the regulator and the battery you will get 60+ volt pulses on your electrical system which would fry most of it.

With the Radio using a different supply I could not detect any RF interference when placed near the regulator,it was probably drowned out by the rubbish from my CRO.

UPDATE I have now built my system and with a 40v RMS supply feeding the regulator there is no detectable noise on recieve. (Unoccupied channel with mute off) On transmit with a monitor reciever same deal. In fact it makes no difference if the 40 v ac is present or not.

Yes that's MINUS 5 degrees C in my shed so progress on the fuse is slow at the moment.

Stay Tuned as the next series of tests will be with ignition interference, I am planning a noise free radio installation.