Forum: GNU Radio Re: why two switches and two Rx in RFX

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Ad81d1e6e8493baa75befee55a8dce64?d=identicon&s=25 Jeffrey Karrels (Guest)
on 2007-07-05 21:14
(Received via mailing list)
Message: 2
Date: Thu, 05 Jul 2007 10:10:15 -0700
From: Matt Ettus <matt@ettus.com>
Subject: Re: [Discuss-gnuradio] why two switches and two Rx in RFX

...

>>
>
>You should NEVER connect the TX output to an RX input without a lot of
>attenuation in between.  You should also not be using RX2 in your situation.
>
>Matt

Question. What is "a lot of attenuation" (ballpark?)  I have a RFX1800
transmitting at "20" going into (cabled) a dbsrx with gain "40".
Between the transmitter and receiver I have 40dB worth of
attenuators... Would you suggest any different? I learnt the hard way
on the first dbsrx :)

Thanks
Jeff
3596cfe1d579c65b9babd35e8787977c?d=identicon&s=25 Matt Ettus (Guest)
on 2007-07-06 05:50
(Received via mailing list)
>
> Question. What is "a lot of attenuation" (ballpark?)  I have a RFX1800
> transmitting at "20" going into (cabled) a dbsrx with gain "40".
> Between the transmitter and receiver I have 40dB worth of
> attenuators... Would you suggest any different? I learnt the hard way
> on the first dbsrx :)

The RFX boards can put out as much as 26 dBm.  The RF inputs can be
damaged by 0dBm.  So use at least 30dB.  But the frontend isn't linear
unless you go even lower.

I get this question a lot, and I don't understand it.  Attenuators are
cheap and they don't charge per dB.  Why not just throw 40 or 50dB in
there and be safe?

Matt
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