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Message-ID: <003501c78c4d$0d68f060$0300a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <c76.efa8d1e.335b9166@aol.com> <004d01c78c3a$48757ec0$0b01a8c0@server>
Date: Wed, 2 May 2007 01:01:33 +0100
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Subject: LF: Re: Passive high-pass filter circuits?
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Status: O

Hi JB your spec might give filter designers the shivers !! There are a
couple of other parameters that would help, though they might seem
unimportant. How fast do you want it to roll-off below 1kHz ...like how far
down should 500Hz be. As a rough guide I think you get 6db/octave per pole
on a simple filter and this determines how many sections you need to meet
your requirement. Also if it is designed at 600 ohms it may have strange
"wind-it-youself" inductor and capacitor values. It is often easier to
design for a given inductor and match it at input and output with capacitor
taps or transformers( there are now several experts squirming I am sure )
You also, in theory, need to quote the acceptable ripple allowed in the pass
band, this is also tied in with the ultimate attenuation in the stop-band.
You have to play the percentages.

I am lazy and do it by cut and try on a network analysis program, sometimes
getting the values from the disc with Wes Haywards book "Intro to RF
Design". That way I get useable filters out of standard Toko coils and a
little paralleling of the caps. Well I call it the "amateur approach" !!

Cheers de Alan G3NYK

----- Original Message -----
From: J. B. Weazle McCreath <weazle@hurontel.on.ca>
To: <rsgb_lf_group@blacksheep.org>
Sent: 01 May 2007 22:47
Subject: LF: Passive high-pass filter circuits?


> Hello LFers,
>
> I'd appreciate it if someone could point me to, or directly send
> to me, a circuit for a high-pass filter designed for use on a 600
> ohm balanced audio line.  A passive RC circuit that rolled off
> everything lower than 1 kHz. or so it would fill my need nicely.
> Thanks in advance to any and all that reply.
>
> 73, J.B., VE3EAR - VE3WZL
> Solar and wind powered
> Lowfer " EAR"  188.830
> EN93dr
>
> http://www.hurontel.on.ca/~weazle
>
>
>