A better phantom power

Jul 24, 2006 4 Replies

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Adam Stouffer 19 years ago

I acquired an old black and white Magnavox MC 3511 CCTV camera (old meaning it uses a camera tube) which runs off phantom power. The only connector is coax style like a car radio antenna but smaller. I removed the connecter and applied 12vdc and coupled the video output through a

2200uF cap in parallel with a .1uF ceramic cap. The format is RF and switchable to channel 3 or 4.

The overall picture quality is pretty bad. Lots of ghosting and distortion and some scan lines going diagonally. What is a better way to couple the RF out? Should the capacitor sizes be any different, should there be some type of choke in series with the incoming power? To answer the least of my questions, what voltage does this camera take? Varying from 9-13vdc gives different results none of which look very good.

Adam

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Michael A. Terrell 19 years ago

You need a choke in the +12 VDC power line to keep the video from being shunted through to ground by the power supply. The secondary of a filament transformer might work ok, as long as you don't saturate the core with the DC.

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida

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amdx 19 years ago

I agree with Michael about the choke. I would add, if the camera output is rf (channel 3/4) the 2200uf may be to large and have excessive losses at

65 mhz. Mike

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blah 19 years ago

That same thought crossed my mind shortly after posting. Must have been thinking composite video, not RF. I'll try some lower value caps and adding a choke maybe a few hundred uH. Thanks for the input.

Adam

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Tam/WB2TT 19 years ago

You need an RF choke in the DC feed. A 2 - 5 uH is about right. I hope you meant 2200 PF, not uF.

Tam

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