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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Asymmetric Stripline / Microstrip online calculators for
 impedance and velocity
Date: Wed, 21 May 2025 16:34:51 +1000
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On 21/05/2025 7:39 am, john larkin wrote:
> On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
> 
>> On 5/20/2025 1:59 PM, Bill Sloman wrote:
>>> On 20/05/2025 11:53 pm, Mike Perkins wrote:

<snip>

> The simple equations, like from the Motorola ECL book, get stupid (as
> in claim negative impedances) for some cases.

The simple equations in the Motorola Data book give good approximations 
to the characteristic impedance in the 50R to 75R range.

Back around 1990, when I needed to cover a wider range of impedances, I 
ended up buying Peter C.L. Yip's "High Frequency Circuit Design and 
Measurements" ISBN 0-412-34160-3. It had only just been published back 
then, and I'd found it in Heffer's in Cambridge U.K. which stocked that 
kind  of book for undergraduate and postgraduate students.

It offered slightly longer equations - including natural logarithm terms 
- which were claimed to stay valid for a slightly wider range of 
characteristic impedances.

Development being what it is, the project got cancelled before the 
relevant printed circuit boards got made or loaded. The precursor boards 
had worked well enough, after we'd tinkered with them, but we'd clearly 
needed to do better.

-- 
Bill Sloman, Sydney