On Wed, Aug 17, 2005 at 12:34:18PM +0800, [EMAIL PROTECTED] wrote: > Hi, all > When I traced the tv_rx.py code, I found that in order to adjust the RF > AGC/IF AGC > the AUX DAC inside the AD9862 must be used. But I had several questions about > this. > > 1). the AUX DAC bit width: in the code segment below, there is a magic number > 4096 > (2e12), but the bit width of AUX DAC is only 8 bits width(2e8=256).What is > the relationship > between the 8-bit and 4096?
2e12 == 2,000,000,000,000. I think you mean 2**12 ;) The interface is specified with a 12-bit value to allow us to possibly update to higher res aux dacs in the the future. The library current just shifts the argument 4 bits right. > 2). the gain/voltage formula: > Are there two formula approximation from the tuner datasheet ? See http://comsec.com/usrp/microtune/NF_tutorial.pdf To get the best noise figure, you max out the RF gain prior to ramping the IF gain. > 3). TV RX daughterboard > In the schematics, it is necessary to have two signals: AUX_DAC_A, and > io_rx_00 > to control the IF AGC setting. What is the use of io_rx_00 signal? Per the schematic R11 and R13 are not loaded. io_rx_00 and io_rx_01 are not used on the TVRX board. Eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
