[Discuss-gnuradio] USRP2 Transmit Power

[MarcW]

Dear all,

We are trying to transmit a carrier using a USRP2 board (done using the
USRP2 constant source example in the UHD branch) and then measure the
received power by using the FFT via another USRP2 board directly connected
to it. However, the fft shows a lower power than specified in the data sheet
(11dBm instead of 17dBm). We have a few questions regarding this:

1.) What are the main factors in hardware and software which affect the Tx
and Rx gain?

2.) We read in the datasheet that the RFX2400 has a transmit power of 17dBm.
However, we observe from the schematic of the RFX2400 that there are two
amplifiers (MGA82563 and RF3315) with output power of 17dBm and 23dBm
respectively. How is the 17dBm figure in the datasheet derived?

3.) In software, what is the point of setting the set_gain parameter in a
USRP2 sink? How does this change the transmit power? Does this change occur
in hardware or in software?

4.) At the receiver side, is there a variable gain amplifier? How does the
gain parameter in the USRP2 source affect the received signal and is this in
hardware or in software? What controls the amplifier?

5.) How do we make sure that we always transmit at the highest possible
power?

Thankyou in advance for any help you can provide.

Best regards,
Marc.
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