At 11:07 PM 5/28/2002 -0600, John W. Childers wrote:
>On a revision of a board, unwanted antennas can remain and must be found 
>and removed.  These are tracks that branch out from a net, but don't 
>terminate on a pad, and can generate noise as electromagnetic waves, much 
>like an antenna on a radio.
>
>Other than visual search, is there any systematic way to find them?

Most stubs can be classified into two kinds: stubs which terminate at a pad 
and stubs which do not. The latter could fairly easily be found by 
analyzing spreadsheet data from a PCB; essentially one would be looking for 
a track which has an endpoint which does not coincide with any other 
endpoint on the same layer, nor does it coincide with a via or pad. "Easy" 
does not mean "quick" unless the utility has already been written....

As to stubs which terminate in a pad, a little more analysis would be 
necessary, but not so much as to become really difficult.

However, there are certain kinds of stubs beyond this. For example, if a 
track connects at one end to a pad and then returns to that pad without 
connecting anywhere else, this would be a stub as well.

Still, it would not be impossible to analyze a database to find stubs. 
Either Protel will add the tool at some time or a user will write a utility 
-- it does not have to be a server, though a server would be more 
convenient -- which would find and flag stubs.

Some stubs might be eliminated by the autorouter; autorouter intelligence 
does encompass most if not all of what is needed to find stubs.

I haven't tried it, but the autorouter might already eliminate some stubs, 
assuming that they are not locked. It seems to me that it once did.

Note that connections made at other than pad or via or track endpoint 
center could make it more difficult to identify stubs....

And fills and arcs would add more complications....


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