Tracks to nowhere?

[Mike Tomlinson]

Posted in another group:

are these tracks for?

[Chris Bartram]

I'd guess it's an antenna.

[John Williamson]

+1. It's about the right size for a printed cellphone system (3G) antenna. Reinforced by the SIM1 and SIM2 letering by it.

[The Natural Philosopher]

they are tuned circuits. open ended transmission lines. Or a bored draughtsman doodling..

[The Natural Philosopher]

ah. could be that as well as a tuned circuit.

[Graham.]

Antennas are tuned circuits.

[Andrew Gabriel]

It's called a microstrip line, and they're used for several different purposes.

Or a delay line - time to send a signal and reflect it from the end.

Particularly given the PCI bridge chip next to it, and that PCI is an unterminated bus which relies on the signal reflection from the far end of the bus in order to work. The bridge chip is creating a new physical PCI bus, and it may be that the tracks to the PCI devices on that bus are too short to meet any minimum track lengths required for signal reflection detection, and need to be artificially lengthed.

I have also seen antennas like this.

[The Natural Philosopher]

Not necessarily. But all tuned circuits are antennae.

[fred]

In article , Andrew Gabriel writes

Tuned length termination stub sounds good to me.

[Man at B&Q]

That's an unlikely explanation. There's no active detection of the reflection involved in PCI, and no minimum trace length. It's just the way the drivers are specified to drive the bus lines.

MBQ

[Tim+]

You mean like Bill's name carved into the cliff of the IOW above = Blackgangs (but below Balckgang Chine)

[Brian Gaff]

Maybe they used to make very big wedding cakes there and when they wanted to move them... There is a song about it Tracks of my Tiers.

OK I'll go to sleep again now.

Brian

[The Natural Philosopher]

(but below Balckgang Chine)

where DID you find THAT.

[Graham.]

(but below Balckgang Chine)

MIkE is even clearer at Whale Chine. Ok look, it's full of them, quite a bit further in the same direction between IRB Sta and The Nodes can be found ROB

[Jethro_uk]

Wasn't the old canard that they were put there to catch people out for copying maps ? I always thought "oh yeah", but a year working with a digital mapping application proved otherwise. And it's really a neat idea.

I wonder if there are any pieces of electronic kit which have a useless component soldered in isolation somewhere, just to be able to snare counterfeits ?

[Tim+]

Read about it somewhere. Apparently bored cartographers have hidden lots of names in map features like this.

Tim

[Bob Eager]

Could even be Robin.

[charles]

my preference is for the farm in the Chilterns called "Hard to Find Farm".

[polygonum]

,

It's very easy to find in these days of Google. :-)

well-known egg producer with their products in many local shops.

[Theo Markettos]

All this makes sense, except... if you look at both sides, the other end of the line doesn't connect to anything. It could possibly be a stub for a buried trace (into a via in the hole) - if a signal was sandwiched between two power planes and then emerge to the surface here. But otherwise I'm having difficulty thinking what you'd put through a cable just to use a bit of PCB as a stub/antenna. Particularly using a pin header as the connector.

But... maybe it's a manufacturing test. Connect your network analyser to the SIM1 or SIM2 pins, check that the board fab is within spec. For PCIe the board parameters matter quite a bit, so if the layers were the wrong thickness this would be something this test would detect.

That's quite a neat idea. I might try it next time a do a fast board.

Theo