[USRP-users] X310 External 10 MHz and 1 PPS specifications

[Kemp, Elizabeth - 1008 - MITLL]

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

[Andy Walls]

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

Post by Kemp, Elizabeth - 1008 - MITLL
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
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[Matt Ettus]

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

Post by Kemp, Elizabeth - 1008 - MITLL
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
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USRP-users mailing list
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

[Marcus D. Leech]

Post by Matt Ettus
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.