Dummy load / direct wire connection concept

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dexter zero-kelvin at gmx.de
Sun Jul 26 19:43:22 UTC 2009


Hi folks,

In order that a rogue GSM-BTS can cause a lot of trouble with the 
regulation offices there is a need for a dummyload solution.

I have 2 ideas in mind:

The first one uses attenuators to set up a direct wired connection:
http://root.runningserver.com/pub/desktop-gsm1.png

The second one uses parasitic coupeling in a shilded box:
http://root.runningserver.com/pub/desktop-gsm2.png

The second solution in my opinion the most save one because the BTS does 
not send directly in its own receiver as well as the MS do not send 
directly into the BTS. But i also think that this solution is too 
crappy, i think there must be a more accurate way.

The first solution fullfilly my demands in accurateness. The impedance 
is 50 Ohms and attenuators ensure that the signal that is transmitted 
between two points are attenuated enough - in theory...

I have no experience in those things, i never connected a sender and a 
receiver directly for measurement proposes. I am afraid to damage BTS 
and/or MS by trying the first solution.

What do you think, what would you do? How do you ensure that you do not 
interfere with the with the official GSM networks? I think sometimes it 
would be very nice to make 100% sure that no HF signals leave the desktop.

PS: One of my inspirations: http://www.comlab.hut.fi/Resources/GSM.html

regards.
Philipp






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