What's in the loop interface box?

MRD · #1 15-03-2010

We need an AMB loop interface box and even a none AMB one is £70+pp so we're toying with the idea of making one, BUT we don't know whats inside one, lol. Does anyone know whats inside?

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simoncrabb · #2 15-03-2010

Here you go:

http://www.rctech.net/forum/electric...-amb-loop.html

Battle_axe · #3 15-03-2010

i think it is just a bnc connector and then two screw down terminals i will mesure whats going on if i remember

MiCk B. · #4 15-03-2010

Can't help you with what's in interface box.

But this is what we use for the outdoor track.

http://www.transponderservices.com/b...parts.html#lib

It's buried under the track (permanently connected to the loop) sealed in a tub. Been like that for the last year and works fine.

MiCk B. :-)

MRD · #5 15-03-2010

Thats the one we were looking at but I'm pretty sure there isn't £70 worth of components in that thing. If it uses normal components it could be made for a fraction of that, its just a case of knowing what they are

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Battle_axe · #6 15-03-2010

Quote:

Originally Posted by MRD

Thats the one we were looking at but I'm pretty sure there isn't £70 worth of components in that thing. If it uses normal components it could be made for a fraction of that, its just a case of knowing what they are

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welll there will without a doubt be a resistor to alter the gain of the loop antenna what else i dont know not allot else as the decoder does the signal prosessing i think

MRD · #7 15-03-2010

Yea, I've heard the unit refered to as a 'choke' and it's the same block for the AMB analoge and digital systems so like you say its not a signal processer, so possibly just a noise surpressor and a regulator of some sort. If I can make them cheap I might stick some on Ebay

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DanW · #8 15-03-2010

Quote:

Originally Posted by Battle_axe

welll there will without a doubt be a resistor to alter the gain of the loop antenna what else i dont know not allot else as the decoder does the signal prosessing i think

The resistor for the loop gain goes mid point in the loop. On the orignal AMB supplied loops its potted in a "black box". The loop its self can be made easily.

The interface box on the end of the co-ax is more difficult... I believe its an impedance matching transformer amonst other bits inside. It means that the signal voltage is stepped up so that the co-ax is running at a higher level than the the loop to improve signal/noise ratio and reduce rogue transponder pick-ups from the co-ax.