Pardon me, but an elliptic filter does not tend toward infinite attenuation
in the stopband! The tradeoff, with elliptical filter designs, in which we
incorporate transmission zeroes to increase the cutoff rate into the
stopband, is finite attenuation in the stopband. Indeed, ultimate
attenuation and ripple are essential specifications that must be
incorporated into the design of an elliptical filter. If really high values
of attenuation are required the elliptic filter can be followed by
Butterworth or other all-pole filter section(s)
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Chuck
Hutton
Sent: Monday, September 22, 2014 3:22 PM
To: topband@contesting.com
Subject: Re: Topband: BCB interference ?
Their description (to me at least) indicates an elliptic filter with a
stopband peak of -40 dB at 1 MHZ and ranging to infinity (in theory)
elsewhere in the stopband. In other words, 40 dB is the maximum for the
discrimination factor.
"Indicates" is a word I feel is necessary as their filter really is poorly
described. They should have said what filter type and order are used and
used standard nomenclature for filter parameters. And there's no mention of
passband ripple.
Chuck
> Date: Mon, 22 Sep 2014 11:21:29 -0700
> From: jim@audiosystemsgroup.com
> To: topband@contesting.com
> Subject: Re: Topband: BCB interference ?
>
> On Mon,9/22/2014 6:50 AM, Ed Stallman wrote:
> > Has anyone used this High Pass Filter ?
> > http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html
>
> The spec for this filter is ambiguous. Is the -40dB at all frequencies
> below 1.6 MHz, or at 1 MHz? BIG difference. OTOH, the Dunestar
> filters are decent for the price.
> 73, Jim K9YC
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