Re: [Discuss-gnuradio] a simple qustion about the attenuator for the SMA cable

[Dan Halperin]

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On Nov 4, 2008, at 2:31 PM, Bill Stevenson wrote:

> I have a rudimentary question about the attenuator. When I was  
> searching some questions in the archive, I found that some guys  
> mentioned when testing the transmitter and receiver for daughter  
> board, the antenna should be connect by Tx/Rx SMA, the Tx and Rx can  
> NOT be connected directly by cable and we need a attenuator about  
> 40-50 dB!! What is the meaning of attenuator here? Is it a hardware?  
> Thanks a lot for all!

An attenuator is a piece of hardware that weakens ("attenuate" means  
weaken) the power of a signal transmitted along a wire. When you  
directly wire a TX board to an RX board, the power transmitted is much  
stronger than receiver expects (even a tiny bit of air gap induces a  
lot of attenuation) and can fry the circuitry. So we simulate this air  
gap with an attenuator.

Fixed RF attenuators can be had for fairly cheap ($10-20) I think.

- -Dan
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