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4hv.org :: Forums :: General Science and Electronics
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VHF Filtering - School report Help

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TechNerd
Wed Nov 10 2010, 09:51AM Print
TechNerd Registered Member #2289 Joined: Thu Aug 13 2009, 02:49PM
Location: Jylland, Denmark
Posts: 19
Hi All

I'm about to write a report on the subject "VHF Filtering"

As I understand it, the filters work like when handeling LF but the higher frequency changes the component values by a certain %.

The main questions are:
What is a 200Mhz filter used for?
What does the filters consist of?
How does digital filtering work at these frequencies

I need some not to complex explanitions on the subject or some weblinks..

hope to get some answers:-D
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Steve Conner
Wed Nov 10 2010, 10:34AM
Steve Conner Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Separating wanted VHF signals from unwanted ones. :P

Inductors and capacitors. At these high frequencies the inductors are air cored with only a few turns, and the capacitors are tiny ceramic ones.

Not very well. Typically it would be done with a very high speed A/D converter and a FPGA. ICs called "digital downconverters" also exist, these can take a small section of the VHF spectrum and translate it down to a lower sampling rate, where more complicated filtering can be done. This can also be done in a FPGA. All of this is expensive, complicated and uses lots of power.
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