> > - What is the maximum voltage can I feed the daughter-board through SMA > ? > Roughly 0dBm would be a safe bet.
Which translates to roughly 0.22V There are several handy places on the web for doing conversions between dBm and voltage: http://www.raltron.com/cust/tools/voltage_to_dbm.asp To pick one at random. Assume 50 ohms impedance for all the daughtercards In RF system design, it's usual to talk in terms of power levels rather than voltages. What you'll generally find is that for RF componentry, maximum input levels are generally quoted in dBm (dB referenced to 1 milliwatt), and sometimes dbuV (dB referenced to 1 microvolt). -- Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ----------------- Hello, thank you for your reply. I found this information in the forum, I think it is from Josh "Input Full Scale on LFRX: +10dBm = 2Vpp = 1 Vpeak = 0.7 Vrms" So I think I can feed the max voltage up to 2Vpp in LFRX, is this right ? I want to know the max voltage just to be sure I will not kill the LFRX. The more important thing is I want to feed the USRP exactly the frequency (about 50Hz) of the line (home) voltage ( 50 Hz, 230V in europe). Afterthat I want to measure this frequency. - Do you have any ideas how can I transform the line voltage in lower voltage of 2Vpp and get the same frequency out ? I think about schmitt trigger or comparator circuit can help. Do you know some tutorial about this ? - To measure the frequency comes USRP, I write a new block using zero-crossing algorithm (base on howto-write-new-block). Please have a look in my cpp code if it is wrong. ------------- float zero[]; int k; for (int i = 0; i < noutput_items; i++){ if (in[i] = 0){ zero[k] = i; k++; } } out = 2*(zero[k]-zero[k-1]); // Tell runtime system how many output items we produced. return noutput_items; ----------------- http://old.nabble.com/file/p29415484/howto_frequency_ff.cc howto_frequency_ff.cc http://old.nabble.com/file/p29415484/howto_frequency_ff.h howto_frequency_ff.h http://old.nabble.com/file/p29415484/howto_frequency_ff.i howto_frequency_ff.i I appreciate your help. Phong -- View this message in context: http://old.nabble.com/zero-crossing-detection.-parallel-inputs-to-USRP-tp29386998p29415484.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
