Close range RF Locator

[key]

I'm new to this, so please bear with me. I'm a software developer, so I don't have a lot of experience with custom hardware..

Basically what I want to come up with is a method that will allow me to locate an object via RF signals. The trick is that the objects will be in close proximity to the 'Locator'. There will be multiple objects, and the locator needs to be able to differentiate between them.

The image in my head is of two 'Locators' that send out pings which are returned by the item to be located. By measuring the lapse in time between when the ping was sent, and when it was echoed, I should be able to find out how far away the object is from the locator. By using this information from both locators, I should be able to pinpoint where the object is (I'll actually have two prospective points, but I will know that one is incorrect - the object to be found will be contained in a certain area, so whichever point is in that area will be the correct point). Am I on the right track here so far?

The trick to this is, and maybe it's simple to overcome, that the objects that need to be found cannot be battery opperated. What I would like is for the objects to be completely self contained. Also, there will not be a direct line of sight between the 'Locator' and the objects that need to be located - which is why I thought of RF.

The distances that this needs to work at are small - about 25-30 feet. Also, the accuracy needs to be very good. I would like to be able to pinpoint the location of an object to within 1/8" of it's actual location.

If you could supply me with any ideas on what kind of materials/methods would be needed to accomplish this I would be grateful. If not, perhaps a link to a web site that would help to educate me on RF location?

Thanks,
Zach

[russlk]

The basic problem is that radio waves travel at 186,000 MILES per second, so 1/8 inch is such a small time you would be extending the state of the art several orders of magnitude if you got this idea to work.

[steven]

:)rf bug sniffer or the car tracker or beeper bug may be what  may intrest you, go to the talking electronics site on the net ,

[windoze killa]

Positioning an object to 25 to 30 ' isn't a problem at all. Trying to do it with an accuracy of 1/8" using RF I think you are delving into the fantasy world.

In a previous job I had we did something very similar but the accurcay over that distance was about 6". We tried RF and ultrasonic and both gave a similar result. I think the only thing that would come close to that accuracy would be laser positioning.

[Muhammad Abu Bakar]

For close proximity the technique is to use Ultra Sonics.  The working is similiar to RF but at much lower frequency.