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Re: [Discuss-gnuradio] WBX power level

From: Charles Brain
Subject: Re: [Discuss-gnuradio] WBX power level
Date: Tue, 15 Jun 2010 08:28:02 +0100

----- Original Message ----- From: "Jason Abele" <address@hidden>
To: "Charles Brain" <address@hidden>
Cc: <address@hidden>
Sent: Monday, June 14, 2010 7:03 PM
Subject: Re: [Discuss-gnuradio] WBX power level

Hi All,

Has anyone measure the power level coming out of their WBX board?

Measured on a Gigatronics 8541 microwave
power meter connected directly at the back of the USRP2 I am getting
(with a CW carrier)

100 MHz about 35 mW
1.3 GHz about 15 mW

Ettus quote

50 - 100 mW< 1.2 GHz
30 - 70mW> 1.2 GHz

I know measuring power is notoriously inaccurate but I was wondering
what others have found.


Please try the following command with non-UHD for comparison:

usrp_siggen_gui.py -x 250k -i 64 --tx-gain=25 -A 1.0  -f 1.3G

You should see about 50mW (17dBm) at 1.30025GHz

If you change the final argument to 100M you should see around
80-100mW (19-20dBm) in the tone at 100.25MHz

If you can confirm those numbers, perhaps we have a constant scalar
missing in either your flowgraph or the UHD code someplace.


Hi Jason,

I got the test done this morning (after I re-installed gnuradio 3.2.2 )


usrp_siggen_gui.py -x 250k -i 16 --gain=25 -a 1.0  -f 1.3G

60mW @   1.3 GHz
126mW @ 100 MHz

Using my code and UHD (my code modified to write  I = 0x7FFF, Q = 0x7FFF)

14.4mW @  1.3 GHz
33.8 mW @ 100 MHz

Using my code and UHD ( my code modified to write  I = 0x7FFF, Q = 0x0)

14.8mW @  1.3 GHz
24.8 mW @ 100 MHz

I ran the power meter's self calibration routine before taking the measurements
this time and applied the correct frequency correction.

Looks like we have a bit missing :-(

- Charles


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