A simple qustion about the attenuator for the SMA cable


#1

Hello, all!!!

I have a rudimentary question about the attenuator. When I was searching
some questions in the archive, I found that some guys mentioned
whentesting 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!

Bill


#2

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On Nov 4, 2008, at 2:31 PM, Bill S. 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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#3

From: Dan H. removed_email_address@domain.invalid
To: Bill S. removed_email_address@domain.invalid
Cc: removed_email_address@domain.invalid
Sent: Wednesday, November 5, 2008 1:08:41 PM
Subject: Re: [Discuss-gnuradio] a simple qustion about the attenuator
for the SMA cable

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On Nov 4, 2008, at 2:31 PM, Bill S. 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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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


#4

On Wed, Nov 5, 2008 at 1:02 PM, Bill S.
removed_email_address@domain.invalid wrote:

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setting --tx-amplitude to a reasonable value. Do you think so? What’s your
idea?

Running full output from the output of the daughter board to the input
my damage the daughterboard. Using an attenuator is safer, avoiding
the possibility of coding errors leading to full output power.

Depending on the ammount you lower the tx-amplitude, you also add
quantization noise.

Philip