My mistake, I am using the BasicRX with the transformer (I was looking at the wrong datasheet). I could go ahead and get a new transformer, but I would ideally like a higher impedance than is offered. I just tried to modify the transformers in the schematic (http://code.ettus.com/redmine/ettus/documents/2) by removing R3 and R9, and then changing R6 and R7 to 1 MOhm, however, this didn't seem to give me a large enough impedance.
Is there a better way to modify the transformer that is on the BasicRX to give me a high impedance? Marcus D. Leech wrote: > > On 09/08/2011 01:08 PM, valentac wrote: >> I have my own RF front end i'm using with the USRP, but it requires a >> High >> impedance load to operate correctly. Since the basic RX daughterboard has >> a >> 50 ohm impedance, I have to modify it or add a separate voltage buffer >> before the input. However, since the basic RX daughter board in the USRP >> has >> an op-amp in its first stage, perhaps I could modify this. >> >> I've tried removing R3 and R9 >> (http://code.ettus.com/redmine/ettus/documents/4), but this did not seem >> to >> load the RF front end sufficiently. Would changing the 348 ohm resistors >> to >> a higher value help increase the input impedance into the basic RX >> daughterboard? If so, how would this affect the output going into the A/D >> (besides the obvious filtering effects). > I'd say consult the data-sheet for the AD8132. But just to clear things > up, you're discussing > the *LF_RX* daughtercard, *NOT* the BASIC_RX, which has no op-amp on > it at all, just a > transformer. > > If your input impedance isn't insanely high, you could use a > transformer. 4:1 broadband impedance > transformers are available fairly cheaply from Mini-circuits, etc. > > > > > -- > Marcus Leech > Principal Investigator > Shirleys Bay Radio Astronomy Consortium > http://www.sbrac.org > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/Modify-the-Basic-RX-Daughterboard-tp32425579p32426977.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
