________________________________ From: Dan Halperin <[EMAIL PROTECTED]> To: Bill Stevenson <[EMAIL PROTECTED]> Cc: discuss-gnuradio@gnu.org Sent: Wednesday, November 5, 2008 1:08:41 PM Subject: Re: [Discuss-gnuradio] a simple qustion about the attenuator for the SMA cable -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (Darwin) iEYEARECAAYFAkkR4SkACgkQy9GYuuMoUJ5w4ACeONoqxFnQ+EEquRngohFnpN9v j6AAoKE20VQNzDoDSOAx4oIaA/KPkOxA =Satt -----END PGP SIGNATURE----- Hello, Dan I got it!Thank you so much! But I think we could also attenuate the transmitted power by setting --tx-amplitude to a reasonable value. Do you think so? What's your idea? Thank you! Bill
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