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Old 09-22-2007, 11:52 AM   #1
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Default AMB Loop

Does anyone know how the AMB transponder loop is constructed. I know there is a resistor at the end, I think its like 470ohm or something like that, then it goes to the black box. What is in that black box? is it just taking the two wires and converting them to coax? Or is there some sort of signal converter in there? Any help?
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Old 09-22-2007, 12:13 PM   #2
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I heard from a few folk that you can just use speaker cable, instead of the stupidly expensive yellow cable they sell.

There must be a sensor or something in the little black box, or how would it pick up the transponders?

Also, you could try emailing AMB. I'm pretty sure there is some stupid law that once something has been retailed for atleast 2 years, you can't withold technical drawings.

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Old 09-22-2007, 12:30 PM   #3
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Quote:
Originally Posted by pc9840 View Post
is it just taking the two wires and converting them to coax? Or is there some sort of signal converter in there?
It is working like that, but the noise level is high. There's probably just another resistor or induction. The resistor at the other end mostly is not needed. In onroad we just tape a wire on the ground (regular wire), but in offroad, when it's digged under ground or placed on rather high bridge the resistor is mandatory.
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Old 09-25-2007, 11:06 AM   #4
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Yes the loop has a 470 ohm resistor in it. Loops are easy to make up, resistors are cheap $.99 for a pack of 5 at radio shack.

The black box on the end of the COAX has a 100k ohm resistor in it and ???? not sure what else. I've used other COAX's with poor results. Like Uga said, the background noise is WAY to high. With other COAX's, if everything is done "right" on the car/truck (not mounted on metal, carbon fiber, servo, battery voltage is good), it will "usually" work. But mostly you get a lot of missed laps.
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Old 09-25-2007, 12:48 PM   #5
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Thanks for the response. Were just looking to not have our LHS spend the 180 for another cable if they don't have too. I think if we just splice some regular 12ga off the little black box with a 470ohm resistor inline everything should work good. We are going to be moving the system back and forth between the our off-road location and on-road location. The "AMB" loop is burried out at the off-road track. So the "home-made" loop will be for on-road.
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Old 09-25-2007, 01:18 PM   #6
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You dont need to go that big on the wire, I think its 18 wire. AMB will sell you any part of the system you want. If you don't want to make one you can buy "just the loop" for "about" $40 shipped.

I have banana jacks on mine, I know others with deans plugs, wire nuts.

http://www.rctech.net/forum/showpost...8&postcount=18
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Old 09-25-2007, 03:50 PM   #7
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You can use pretty much any wire you like, the last loop I made up was with a really thin (about 1.5mm) wire and it works just fine.

You don't even need the resistor in the loop for it to work properly, the resistor is just there to help balance the signal. We have cut our original loop just after the black box part, and put a connector on, then made up loops for our tracks with the opposite connector on so we've always got a spare with us
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Old 09-25-2007, 09:57 PM   #8
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I've been using twisted pair telephone wire with no problems at all for the last 5 or so years. We tape it to the concrete and put the rug over it. I just buy a spool of telephone cable at Radio Shack, strip the out sheathing and untwist the twisted pair, tape to the concrete and wire nut it to the split comming out of the black box on the coax. I used the same method when I was running our parking lot program at the LHS. In two seasons outdoors I had only one person cut the loop. We puled the tape back, twisted the ends back together and retaped it and we were good to go. I know of other parking lot tracks that do the same thing without problems. Way less expensie then an AMB loop and the wire is thin enough so that 1/12 cars don't ave any issues I've used 22ga in the past but you can fell it under the carpet with a 1/12 car.
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Old 10-01-2007, 04:58 AM   #9
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How wide is the distance between the two wires for your loop ? I know (I think)in the AMB manual is states 450mm but has anyone experimented with making this distance wider or smaller ? and if so what effect does it have.
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Old 10-01-2007, 09:28 AM   #10
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...I've run loops using 2 strand 22ga speaker wire as close as 8" apart and as far as 15" inches. With tracks as narrow as 12 ft and as wide as 33 ft.

I've had no problems with any of those layouts...and in general the loop wire was DUCT TAPED to the track surface.

If/When I am forced to use a Bridge, I use larger wire, just because the loop ends up quite a bit higher and further away from the transponders...so I figure It can't hurt to have a larger wire for a stronger signal. (I use the small wire on the ground to make the smallest BUMP possible)
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