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.
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