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LC filters

lobstermash

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#1
After Paul mentioned this in another thread, I thought this was a good catch to post about LC filters. I've been running off 2 different packs so far to avoid the issues and see how much power my vtx and camera were drawing. My conclusion is the power used by these components that it's not worth running 2 packs. When running two packs, there's virtually no interference except on high throttle (launch), which I'm thinking is probably vibration rather than interference.

I've got a 5000mAh 3s to chuck in the Bix. I've also got an old PC power supply full of capacitors and ferrite rings, so no excuse not to make up a lc filter and run the Bix FPV off just this pack. There's a long thread on RCG about lc filters and a great vid on there showing the difference in video quality (http://www.rcgroups.com/forums/showthread.php?t=1339007).

Out of the PC power supply, the most suitable capacitor is a 16V 2200uF. The rest are either much lower uF and high voltage or same uF and just 10V. For those wondering, the side with - - - is the negative. The Voltage specified is the max voltage that the capacitor can handle. The uF (or micro Farad rating) is the measure of the storage capacity of the capacitor. Like a battery, the higher the capacity, the larger the capacitor, but this doesn't affect it's ability to do its job.
 
#2
470 uf will work fine, 2200 uf is overpowered. Some people get worse signal because of the higher capacity and more winds on the ferrite ring. If you do so you can affect the range of your rc system/fpv signal... I am going to make a review/build log/faq video about the lc filter. Also you should not wrap the ground wire arround the ferrite ring, you can get problems with your osd if you do that.
 
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lobstermash

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#3
I'm not quite sure how a larger capacitor could possibly reduce your range... It simply holds charge to boost any lows caused by the ferrite's filtering. I've got 14 turns on the ring and I've wound the ground in with the positive. I've read this can affect the GPS's ability to lock on initially and re-lock if there's a disruption. Some have reported that there was still interference when the ground isn't included.