[USRP-users] interpretation of received signal

Neel Pandeya neel.pandeya at ettus.com
Wed Oct 18 03:03:04 EDT 2017

Also note that at 0 dBm, you're at the maximum safe input power, so your
received signal might be saturated.

--Neel Pandeya

On Oct 17, 2017 22:30, "Marcus D. Leech via USRP-users" <
usrp-users at lists.ettus.com> wrote:

On 10/18/2017 12:08 AM, Nirmala Soundararajan via USRP-users wrote:

> Hi all,
> I am trying to transmit and receive a simple 10 kHz tone using a single
> USRP B205mini-i. The input power is 0 dbm ( The amplitude of 10kHz tone
> being 45mV). The transmitting and receiver antenna are same omnidirectional
> type each having 3 dbi gain. I set the transmitter gain as 8 and receiver
> gain as 70. The carrier frequency is around 800 MHz. The path loss comes to
> around 20 db considering the fact that transmitting and receiving antenna
> are just a foot apart. ( I took far field and did not consider near field)
> The received spectrum shows -26 dbm. How should I interpret these results?
> regards
> Nirmala
> How did you get -26dBm?

Unless you have painstakingly *calibrated* your USRP B205mini, and wrote
code that converts the received data into dBm, given your carefully-derived
  calibration tables, an FFT will simply show received power relative to
the mathematical maximum in the system.

Further, given that modulating signals in the SDR world are purely digital
number, how did you derive a figure of 45mV of modulation?

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