Request for help with Passive VLF front end filter design

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philwinder

Joined: 29 Jan 2007
Posts: 40

29 Jan 2007 2:33 Request for help with Passive VLF front end filter design

Hi, im designing an electrostatic reciever that works from approx. 0.1 - 15 Hz but im obviously getting loads of mains noise.
I have some simple active filters after the initial gain stages, but is there a way to filter the noise before the initial gain stage?
Normally this should be ok, but heres the snag: the receiver has to have a very high input impedance (trying to read fA) and the only way i can figure out how to do this is for the filter NOT to have a connection to ground, i.e. all the resistances/impedances add up in series and do not affect the overall Tohm input impedances. Is there a passive filter out there that does not need a ground connection?
It can either be a 50Hz notch, or a 20Hz low pass.

Many thanks,

Phil Winder

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javadiiiii

Joined: 21 Feb 2008
Posts: 6

05 Mar 2008 14:25 Request for help with Passive VLF front end filter design

Hello
First I want to thank you for your great forum because it has the best resource that I've ever found on web about VLF receivers.
I am an Electrical Engineering Student. Since I'm very interested in Astronomy As my Thesis I want to build a Circuit to detect the meteors using a VLF receiver. Then I want analyze the spectrum using a computer and count the number of meteors entered the ionosphere.
I found much useful info on your forum but I need some guide from you.
Would you please tell me what is the best low-noise VLF receiver circuit that is Suitable for detecting meteors? And do you think it is practical to make distinction between spectrum of meteors and other phenomena?
Any useful guide about this topic will be appreciable
I am waiting for your answers . . .