Re: [Discuss-gnuradio] RFX2400 Transmit power

[Martin Braun]

Yep,

Brian's right. Doing what you propose would be equivalent to reducing
the DAC to ~7bit and thus reducing signal-to-quantisation-noise-ratio by
54dB (!). You don't want that.

Try subdev.set_gain(). You can see the available gain range with
subdev.gain_range() (subdev is the object to access the subdevice, try
usrp.selected_subdev() ). Perhaps that will help.

MB


On Wed, Jan 21, 2009 at 01:05:50AM -0500, Brian Dunn wrote:
> Hi Yong,
>
> I think with maximum signal levels of +/- 45 on the digital side your 
> signal would be severely distorted due to quantization noise. Perhaps the 
> easiest thing to do would be to put a mini-circuits attenuator inline with 
> the SMA output of the RFX2400 board? Not sure if this will work for your 
> application though.
>
> -Brian
>
>
> On Jan 20, 2009, at 8:37 PM, Yong J. Chang wrote:
>
>>
>> Hi, all!
>>
>> Now I'm using USRP1 and RFX2400 d'board. In our project, we have to be 
>> able
>> to reduce transmit power down to -40dBm. Please correct me if my approach 
>> is
>> wrong.
>>
>> If we set tx_pga=0dB, the transmit power only depends on the level of
>> signal. So, +/-32767 can give us maximum transmit power 17dBm because the
>> maximum transmit power of RFX2400 is 17dBm.
>>
>> Since the power is a square of signal level, we can get -40dBm if we 
>> choose
>> signal level +/-45 roughly.
>>
>> Am I right?
>>
>> -- 
>> View this message in context: 
>> http://www.nabble.com/RFX2400-Transmit-power-tp21575529p21575529.html
>> Sent from the GnuRadio mailing list archive at Nabble.com.
>>
>>
>>
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-- 
Dipl.-Ing. Martin Braun           Phone: +49-(0)721-608 3790
Institut fuer Nachrichtentechnik  Fax:   +49-(0)721-608 6071
Universitaet Karlsruhe (TH)       http://www.int.uni-karlsruhe.de/

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