Hi, Does anyone know what the input requirements are for the rear-panel external 10 MHz reference input and the 1 PPS input? I am using an OctoClock-G and will need to connect it to USRPs that may be as far away as 50 ft. I'm trying to determine if the signal level at the USRP input will be sufficient. The OctoClock-G output specs are typ. ~1.4 Vpp square wave for the 10 MHz output (50 ohm output impedance), and a 5V logic-level pulse for the 1 PPS output, according to the data sheet. Thanks, Liz

For the PPS in, 5V and 50 ohms (non-DC). See page 12 of the schematic which shows the 49.9 ohm resistor and a 1k/2k voltage divider. http://files.ettus.com/schematics/x300/x3xx.pdf Depending on the Vin min of the SN74AUP1T17 Schmitt trigger, you might be able to get away with something less than 5 V. Regards, Andy On September 23, 2014 5:28:32 PM EDT, "Kemp, Elizabeth - 1008 - MITLL via USRP-users" <usrp-users@lists.ettus.com> wrote: >Hi, > >Does anyone know what the input requirements are for the rear-panel >external 10 MHz reference input and the 1 PPS input? > >I am using an OctoClock-G and will need to connect it to USRPs that may >be as far away as 50 ft. I'm trying to determine if the signal level >at the USRP input will be sufficient. The OctoClock-G output specs are >typ. ~1.4 Vpp square wave for the 10 MHz output (50 ohm output >impedance), and a 5V logic-level pulse for the 1 PPS output, according >to the data sheet. > >Thanks, >Liz > > >------------------------------------------------------------------------ > >_______________________________________________ >USRP-users mailing list >USRP-users@lists.ettus.com >http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

50 feet should not be a problem unless you were to use some really horrible cable. Matt On Tue, Sep 23, 2014 at 2:28 PM, Kemp, Elizabeth - 1008 - MITLL via USRP-users <usrp-users@lists.ettus.com> wrote: > Hi, > > > > Does anyone know what the input requirements are for the rear-panel > external 10 MHz reference input and the 1 PPS input? > > > > I am using an OctoClock-G and will need to connect it to USRPs that may be > as far away as 50 ft. I’m trying to determine if the signal level at the > USRP input will be sufficient. The OctoClock-G output specs are typ. ~1.4 > Vpp square wave for the 10 MHz output (50 ohm output impedance), and a 5V > logic-level pulse for the 1 PPS output, according to the data sheet. > > > > Thanks, > > Liz > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >

On 09/23/2014 06:08 PM, Matt Ettus via USRP-users wrote: > > 50 feet should not be a problem unless you were to use some really > horrible cable. > > Matt > Even RG-174 (about the most-awful cable I'd consider for a 50ft run) has only 3.3dB/100ft at 10MHz, so should be fine. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org