[Top][All Lists]

## Re: [Discuss-gnuradio] Problem setting transmit gain values....

 From: Kshitij Kumar Singh Subject: Re: [Discuss-gnuradio] Problem setting transmit gain values.... Date: Thu, 31 Jan 2008 15:17:43 -0500

```On Thu, 2008-01-31 at 11:33 -0800, Matt Ettus wrote:
> Kshitij Kumar Singh wrote:
> > Hi,
> >
> >   I tried out a simple script to get the gain range of the USRP (I had read
> > in earlier mail archive
> > that we were provided a single gain knob to tune over the entire range of 0
> > to 90 dB):
> >
>
> There is no gain control on transmit with the RFX boards.  There is 90dB
> of gain range on the RECEIVE side.
>
> To change transmit power, you need to lower the level of the signal you
> send.  So +/-32767 is max power, +/-16383 is 6dB less power, +/-8192 is
> 12 dB less power, etc.
>
> Matt
Thanks Matt .. I was just trying out things by myself after reading
usrp_siggen.py and got had these few doubts.
I had another question regarding the 'u.tune()' method. Let me explain
my problem. I tried generating a sinusoid at 2.39G. I got a DUC
frequency of -43M. The tuning results were: Baseband: 2.396G, DUC freq =
-6M. I understand that since we use an IF, our LO on the RFX board was
tuned to 2.396G ( goes from 2.3 to 2.7G in steps of 4M), the IF came in
at around 6M so we got 2.396+0.006 and 2.396-0.006 and chose the latter.
Is this correct? But what about the -43M from usrp.calc_dxc_freq() ?
I also tried transmitting at 2.396+6= 2.402G but then the tuning results
were:
Baseband:2.408,DUC=-6M. Why always a negative DUC freq(why not 2.396
+0.006)?
Could you please explain this "tuning is a two step process" using a
small numerical example? Thanks in advance and sorry for bugging you
guys constantly. I tried reading  usrp.py but got confused.

Regards,
Kshitij

```