I am not familiar with the method you described, or maybe I just can't
visualize it from your description.

I have seen something similar in CATV amplifiers.  Basically it is a
"variable" capacitor.  Imagine a 3 or 4 small rectangles of copper separates
by about .050".  These copper rectangles are on an outer layer and are
placed over a ground plane (internal or external, on the other side).  One
of these rectangles is connector to the circuit node you want to tune
thereby adding a little capacitance at that point.  There are openings in
the soldermask centered between each rectangle that are large enough to
expose copper from the two rectangles adjacent to it.  The technician then
tunes the circuit by adding solder "blobs" to short adjacent rectangles to
the first one, thereby increasing the capacitance at the node being tuned.

I can't vouch for the effectiveness of this method, but I have seen it on
equipment from a couple different manufacturers.

I hope this helps.

<><><><><><><><><><><><><><><><><><>
Chris Stack
Project Manager
dB-tronics, Inc.
145 Tradd Street
Spartanburg SC 29301
Ph. (864) 574-0155 ext 115
Fax (864) 574-0383
http://www.dbtronics.com
Supporting Broadband Networks Worldwide
<><><><><><><><><><><><><><><><><><>

>
>Date:    Fri, 13 Mar 1998 10:17:44 -0800
>From:    Mitch Morey <[log in to unmask]>
>Subject: DES:"tuning" etch pattern
>
>This question came up recently, and I'm unfamiliar with the practice.
>
>A circuit was described to me that has a "few" traces going between
>components, and then they go off the last (first?) component a "certain"
>distance then tie to ground. Sound familiar? This "certain" distance is to
>be determined during routing, and then the three or four (or more) traces
>will be "adjusted" accordingly to satisfy the circuits function.
>
>First off, this makes no sense to me.
>
>Secondly, is there a preferred way to tie these traces to ground, and
>what methods have been used to "trick" the software package you're
>using into doing this (other than showing them as ground signals)?
>
>Any help is appreciated.
>
>Mitch Morey
>Sr PCB Designer
>
>------------------------------
>

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