Re: [Discuss-gnuradio] Setting tx_gain > 20 dB => no effect? (USRP2, XCVR2450)

[Josh Blum]

On Mon, Jun 21, 2010 at 5:31 AM, Sven Oliver Kreis
<address@hidden> wrote:
> Hi there,
>
> I am using an USRP2 with Gnu Radio Companion 3.3 and XCVR2450 as
> daughterboard. I created a simple signal generator with grc.
>
> Signal Source (Sample Rate 12.5M, Waveform: Sine, Frequency: 1,
> Amplitude also 1, Offset 0) connected to USRP2 Sink (Interpolation 128,
> Frequency: 2,481GHz)
>

1.0 is the maximum amplitude. sounds like your clipping and saturating.

try bumping that down by half or so before taking measurements

-Josh

> I am also using one micaz node for RSSI Measurement. (using RssiToSerial
> and a serial programming board) Distance between SDR and micaZ about
> 0.5m.
>
> Taking 10000 RSSI Values per dB Step (stopping, changing Gain +1 in
> USRP2 Sink, starting again with GRC ) I got the attached result.
> (attached max RSSI value, can also attach average value, which looks
> similar if requested)
>
> I started at 0 dB Gain, so x= 1 <=> 0 dB GAIN at USRP2 Sink.
>
> Noise floor is at -97 dBm (not in the plot). Starting USRP2 with Gain 0
> gets it to about -62/-63 dBm at 0.5m distance.
> Increasing gain increases RSSI value as expected. Not quite linear but I
> expected that.
>
> At a gain of 20 the RSSI value reaches about -46 dbM. Increasing USRP2
> Sink gain over 20 doesn't change anything. It seems to stay at about
> -46/-45 dBm.
>
> Printing gain range results in 0 to 30 dB. Also mingain = 0 and maxgain
> = 30.
>
> How to get more tx_gain? Something I do wrong there to make gain > 20
> take effect?
>
> I can also attach the python code, if requested.
>
> Thx in advance
> Sven Oliver
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>