Connect two WBX daugterboards

GNU Radio
1

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

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2

On 15/04/2011 2:45 PM, Brook L. 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.

3

On 04/15/2011 11:56 AM, Marcus D. Leech wrote:

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.

This subject comes up a lot.

Considering how often this one gets asked, might it be worthwhile to
include a little slip of paper in the transceiver boards’ packaging that
specifically addresses it? It wouldn’t make its way to every user, but
it seems like a good start.