Re: [Discuss-gnuradio] RFX2400 Transmit power

[Matt Ettus]

Yong J. Chang wrote:
> Thanks all!
>
> As I know so far, RFX2400 doesn't have amplifier we can control. So
> set_gain() doesn't affect any transmit power. Right?
> Now I'm trying to control PGA gain on FPGA side, but I confused. AD9862 has
> pga which can be controled in range [0 ~ -20dB]. 
>
> self.u.set_pga(0,-20)
> pga_gain = self.u.pga(0)
> print 'PGA gain ',pga_gain        
>   

You can use the PGA to reduce the gain on the RFX-series boards, but the 
problem is that the analog bias points for the quadrature modulator will 
change.  You may be able to reduce 5-10 dB, but it may not operate well 
beyond that. 

The other way to change the output power is to reduce your digital level 
sent over the USB.  Yes, this will reduce your dynamic range, so you 
won't want to do -40dBm this way, but 10 or 20 dB in reduction is fine.

Matt