Re: [Discuss-gnuradio] Connect two WBX daugterboards

[Marcus D. Leech]

On 15/04/2011 2:45 PM, Brook Lin wrote:
> Hi All,
>
> I am using two USRP N210 with WBX. Can I connect two WBX with cable
> directly? Or I need an attenuator between them. If so, what kind of
> attenuator I need.
>
> Thanks in advance,
> Brook
This subject comes up a *lot*.

Generally, the RX portions of all the USRP-family daughter-cards (except 
the BASIC_RX and LF_RX) are designed to receive
  *off-air* signals directly from an antenna.  Driving them directly 
from the TX side risks destroying the sensitive
  low-noise-amplifier (and possibly other) portions of the RX chains.  
This is true of *any* reasonably-sensitive receiver
  that is designed for off-air signals--not just a quirk of USRP-family 
daughter-cards.

In a "from the antenna" receive chain, signals of as low as -100dBm are 
usually easily discernible, and at -40dBm are usually
  of excellent quality, depending on the signal bandwidth, modulation 
involved, receiver-side sophistication, etc, etc.

What you want to do is to make sure that the RX chain receives a signal 
of no more than about -20dBm (10 microwatts--plenty!!).  So
  I'd go with a 20 to 30dB attenuator if you're going to cable them 
together.