Hi Nick,

yes, the Octoclock-G will output the 10 MHz from the undisciplined
oven-controlled oscillator if no GPS is available.

Best regards,

Marcus


On 08.07.2016 07:05, Nick B wrote:
> I'm not super familiar with the octoclock-g, will it produce an output
> if the GPS isn't locked?  I see what looks like a disconnected GPS
> Antenna connector, which would make it unlikely for the GPS to ever lock.
> Nick
>
> On Fri, Jul 8, 2016 at 12:12 AM, Pavan Yedavalli <[email protected]
> <mailto:[email protected]>> wrote:
>
>     It's an Octoclock-G
>     (https://www.ettus.com/product/details/OctoClock-G is what I
>     ordered). And yes, that is true about the external clock inputs
>     and GPS lock. Does that matter if it's an Octoclock-G?
>
>     On Thu, Jul 7, 2016 at 7:46 PM, <[email protected]
>     <mailto:[email protected]>> wrote:
>
>         Is this an Octoclock, or Octoclock-G?
>
>         If it's just an Octoclock, then it has no internal clocks, and
>         acts as a high-quality clock/pps distributor.
>
>         I notice you don't have the external clock inputs connected to
>         anything, and there's no GPS LOCK indicator.
>
>          
>
>          
>
>          
>
>          
>
>         On 2016-07-07 17:08, Pavan Yedavalli wrote:
>
>>         Hi Marcus,
>>
>>         I did what you suggested by wrapping the timed commands as
>>         follows:
>>
>>         For the TX side (what you sent me in for_pavan.py):
>>
>>                
>>         self.uhd_usrp_source_0.set_time_unknown_pps(uhd.time_spec())
>>             now = self.uhd_usrp_source_0.get_time_now()
>>             start_time = now + uhd.time_spec(.5)
>>             self.uhd_usrp_source_0.set_command_time(start_time)
>>                 self.uhd_usrp_source_0.set_clock_source("external", 0)
>>                 self.uhd_usrp_source_0.set_time_source("external", 0)
>>                 self.uhd_usrp_source_0.set_clock_source("external", 1)
>>                 self.uhd_usrp_source_0.set_time_source("external", 1)
>>                 self.uhd_usrp_source_0.set_samp_rate(samp_rate)
>>                
>>         self.uhd_usrp_source_0.set_time_unknown_pps(uhd.time_spec())
>>                 self.uhd_usrp_source_0.set_center_freq(rx_center_freq, 0)
>>                 self.uhd_usrp_source_0.set_normalized_gain(rx_gain, 0)
>>                 self.uhd_usrp_source_0.set_antenna(Antenna_sel, 0)
>>                 self.uhd_usrp_source_0.set_center_freq(rx_center_freq, 1)
>>                 self.uhd_usrp_source_0.set_normalized_gain(rx_gain, 1)
>>                 self.uhd_usrp_source_0.set_antenna("TX/RX", 1)
>>             self.uhd_usrp_source_0.clear_command_time()
>>
>>         And for the RX side (B210_Phase_Viewer.py):
>>
>>                
>>         self.uhd_usrp_sink_0.set_time_unknown_pps(uhd.time_spec())
>>             now = self.uhd_usrp_sink_0.get_time_now()
>>             start_time = now + uhd.time_spec(.5)
>>             self.uhd_usrp_sink_0.set_command_time(start_time)
>>                 self.uhd_usrp_sink_0.set_clock_source("external", 0)
>>                 self.uhd_usrp_sink_0.set_time_source("external", 0)
>>                 self.uhd_usrp_sink_0.set_subdev_spec("A:0", 0)
>>                 self.uhd_usrp_sink_0.set_clock_source("external", 1)
>>                 self.uhd_usrp_sink_0.set_time_source("external", 1)
>>                 self.uhd_usrp_sink_0.set_subdev_spec("A:0", 1)
>>                 self.uhd_usrp_sink_0.set_samp_rate(samp_rate)
>>                 self.uhd_usrp_sink_0.set_center_freq(915e6, 0)
>>                 self.uhd_usrp_sink_0.set_gain(1.5, 0)
>>                 self.uhd_usrp_sink_0.set_center_freq(915e6, 1)
>>                 self.uhd_usrp_sink_0.set_gain(1.5, 1)
>>             self.uhd_usrp_sink_0.clear_command_time()
>>
>>
>>         However, it still does not work when I have the phase viewer
>>         running and stop and restart the for_pavan.py flowgraph. I
>>         had a run of three straight where the phase offset was around
>>         11 degrees, but then afterward it started fluctuating again
>>         (-140, 45, 81 degrees, etc.).
>>
>>         Attached is the front of the Octoclock. I believe the
>>         settings are correct, but maybe something is wrong with that.
>>         Note that the PPS flashes (but I couldn't capture when it
>>         flashed in the picture). Also note that I get the thread
>>         priority warning when running each of them, but I don't think
>>         that is a problem.
>>
>>         I am really not sure what the issue is here, sadly. Thanks
>>         again for your help and patience.
>>          
>>
>>         On Wed, Jul 6, 2016 at 6:22 PM, Marcus D. Leech
>>         <[email protected] <mailto:[email protected]>> wrote:
>>
>>             On 07/06/2016 09:04 PM, Pavan Yedavalli wrote:
>>>             Hi Marcus,
>>>              
>>>             Trying the attached code with two of the USRPs
>>>             transmitting, and with the B210_Phase_Viewer for the
>>>             other 2 USRPs receiving, still gives me different
>>>             offsets for every different run call. And by different
>>>             run call, I'm simply running the flowgraph once, seeing
>>>             the offset, stopping the graph, and then running it
>>>             again, seeing the new offset, and so on. I must be doing
>>>             something wrong here. A you mentioned, since all of them
>>>             are using the Octoclock, that means that they all are
>>>             having the same reference and pps, but both receive
>>>             boards may also not be timed in an aligned fashion for
>>>             the same reason, right? So the receive side LO offsets
>>>             could also be causing problems in narrowing down the
>>>             issue, I'm assuming? Thanks again.
>>             Yes, the receive side needs to be as mutually-coherent as
>>             possible as well.
>>
>>             Also, I forgot to mention that you'll need to modify the
>>             output of the flow-graph I provided to wrap timed-command
>>             stuff around the tuning.
>>
>>             Same on any RX flow-graph.  That's the only sane we to be
>>             able to measure any kind of phase-offset that you can trust.
>>
>>             If the RX side is a B210, you don't need to do timed
>>             commands (and, indeed, they aren't supported for tuning
>>             on the B210).  What I'd do is
>>               leave the RX side running, while you bring the TX side
>>             up and down.
>>
>>
>>
>>>
>>>             On Wed, Jul 6, 2016 at 5:47 PM, Marcus D. Leech
>>>             <[email protected] <mailto:[email protected]>> wrote:
>>>
>>>                 On 07/06/2016 02:48 PM, Pavan Yedavalli wrote:
>>>>                 I disconnected the MIMO cable and now have all 4
>>>>                 directly connected to the Octoclock, but I get the
>>>>                 same results in which the offset changes at every
>>>>                 run (using the above code).
>>>                 What about the attached code?
>>>
>>>                 Keep in mind that you'll have to measure it with
>>>                 something that is also mutually coherent.
>>>
>>>
>>>
>>>>
>>>>                 On Tue, Jul 5, 2016 at 9:11 PM, Marcus D. Leech
>>>>                 <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>>                     On 07/05/2016 11:45 PM, Pavan Yedavalli wrote:
>>>>>                     Yes, sorry - two of them are actually
>>>>>                     connected via MIMO cable, with the master
>>>>>                     connected to the Octoclock. Then the other two
>>>>>                     are directly connected to the Octoclock. I
>>>>>                     used the MIMO cable just because I had it, but
>>>>>                     hopefully that's not changing the functionality.
>>>>>                      
>>>>>                     Yes, I added even more attenuation because the
>>>>>                     Tx gain was already quite low. Thanks for the
>>>>>                     suggestion.
>>>>                     So, a useful experiment would be to do your
>>>>                     coherent TX from a pair that are both hooked up
>>>>                     to the Octoclock.
>>>>
>>>>
>>>>
>>>>>
>>>>>                     On Tue, Jul 5, 2016 at 7:29 PM, Marcus D.
>>>>>                     Leech <[email protected]
>>>>>                     <mailto:[email protected]>> wrote:
>>>>>
>>>>>                         On 07/05/2016 09:45 PM, Pavan Yedavalli wrote:
>>>>>>                         According to the spectrum analyzer,
>>>>>>                         there's nothing being transmitted in the
>>>>>>                         900 MHz band around me, so that is
>>>>>>                         actually fine. The biggest unknown could
>>>>>>                         be what you are saying about how they
>>>>>>                         combine in the RSSI circuit (which I'm
>>>>>>                         not sure how it works).
>>>>>>
>>>>>>                         I am not gaining any more insight when
>>>>>>                         using over-the-air antennas, so I used 2
>>>>>>                         USRPs as transmitters and 2 as receivers,
>>>>>>                         connected them directly with SMA cables
>>>>>>                         (and attenuation), and used Derek Kozel's
>>>>>>                         B210_Phase_Viewer on the receive side to
>>>>>>                         see whether they were aligned after each
>>>>>>                         run. And I am noticing that they are not.
>>>>>>                         The first run produced a 125 degree phase
>>>>>>                         offset, while the second one produced a 3
>>>>>>                         degree phase offset, and this continues
>>>>>>                         to fluctuate after each run (see
>>>>>>                         attached). Note that I am using the code
>>>>>>                         that I pasted above to transmit.
>>>>>>
>>>>>>                         I must be doing something wrong with the
>>>>>>                         code, or not wrapping the timed commands
>>>>>>                         around the correct code. I am not sure
>>>>>>                         though. Thanks again.
>>>>>                         Looks like you have a bit of clipping as
>>>>>                         well.  Back off the gain on the TX side.
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>>                         On Tue, Jul 5, 2016 at 5:51 PM, Marcus D.
>>>>>>                         Leech <[email protected]
>>>>>>                         <mailto:[email protected]>> wrote:
>>>>>>
>>>>>>                             On 07/05/2016 08:20 PM, Pavan
>>>>>>                             Yedavalli wrote:
>>>>>>>                             I see, but the offset in phase
>>>>>>>                             between the two radios will affect
>>>>>>>                             the amplitude, right? That was the
>>>>>>>                             assumption I was using, since it
>>>>>>>                             gives out an amplitude reading, but
>>>>>>>                             the phase clearly will affect that
>>>>>>>                             reading, I presumed.
>>>>>>>
>>>>>>>                             Unfortunately, I don't have any
>>>>>>>                             documentation on the RSSI circuit
>>>>>>>                             apart from the following description
>>>>>>>                             from the vendor:
>>>>>>>
>>>>>>>                             The RSSI functionality allows the
>>>>>>>                             sampling of the received signal to
>>>>>>>                             provide an indication of the amount
>>>>>>>                             of energy being harvested. When DSET
>>>>>>>                             is driven high the harvested DC
>>>>>>>                             power will be directed to an
>>>>>>>                             internal sense resistor, and the
>>>>>>>                             corresponding voltage will be
>>>>>>>                             provided to the DOUT pin. The
>>>>>>>                             voltage on the DOUT pin can be read
>>>>>>>                             after a 50μs settling time. RSSI
>>>>>>>                             shows the actual power level that is
>>>>>>>                             being received at the antenna. This
>>>>>>>                             number is accurate from 0.04mW to 50mW.
>>>>>>>
>>>>>>>                             This probably does not help at all
>>>>>>>                             to debug. Sorry about that.
>>>>>>                             You're making assumptions about how
>>>>>>                             your signals will combine in that
>>>>>>                             RSSI circuit, and how they'll combine
>>>>>>                             with other ambient signals within
>>>>>>                               your frequency band.  I cannot
>>>>>>                             imagine that being stable.
>>>>>>
>>>>>>                             To measure the phase between two
>>>>>>                             signals, you need a device that is
>>>>>>                             phase sensitive (like, for example,
>>>>>>                             another USRP with two inputs), and
>>>>>>                               compute conjugate multiplication
>>>>>>                             between them, or the phase-angle, via
>>>>>>                             the complex-argument block.
>>>>>>
>>>>>>                             Or just plot the two signals on a Qt
>>>>>>                             Time sync, and observe that the phase
>>>>>>                             relationship is the same--that of
>>>>>>                             course requires that your
>>>>>>                               receiver system is internally
>>>>>>                             coherent between the two channels.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>>                             On Tue, Jul 5, 2016 at 4:42 PM,
>>>>>>>                             Marcus D. Leech <[email protected]
>>>>>>>                             <mailto:[email protected]>> wrote:
>>>>>>>
>>>>>>>                                 On 07/05/2016 07:28 PM, Pavan
>>>>>>>                                 Yedavalli wrote:
>>>>>>>>                                 The way I'm doing it is the
>>>>>>>>                                 following (please correct me if
>>>>>>>>                                 there is a fundamental error in
>>>>>>>>                                 assumptions): I am actually
>>>>>>>>                                 using an RSSI circuit that is
>>>>>>>>                                 receiving the power from the
>>>>>>>>                                 USRPs/antennas, and I'm
>>>>>>>>                                 determining whether the phase
>>>>>>>>                                 offset is the same based on
>>>>>>>>                                 that RSSI value. For example, I
>>>>>>>>                                 run the flowgraph once, and I
>>>>>>>>                                 get an RSSI value on the other
>>>>>>>>                                 side of 2.5 mW, but when I run
>>>>>>>>                                 the flowgraph again, it
>>>>>>>>                                 produces an RSSI value of 9.5
>>>>>>>>                                 mW. In my mind, if that offset
>>>>>>>>                                 was constant, then it would
>>>>>>>>                                 have produced something around
>>>>>>>>                                 2.5 mW again. I know this adds
>>>>>>>>                                 another variable to the mix,
>>>>>>>>                                 but I have confirmed the
>>>>>>>>                                 accurate functioning of the
>>>>>>>>                                 RSSI circuit/receiver as well
>>>>>>>>                                 as the static nature of the
>>>>>>>>                                 channel, so its reading is very
>>>>>>>>                                 reliable.
>>>>>>>                                 Could you describe this RSSI
>>>>>>>                                 circuit?  Normally, they're only
>>>>>>>                                 sensitive to amplitude, not phase.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>                                 On Tue, Jul 5, 2016 at 4:19 PM,
>>>>>>>>                                 Marcus D. Leech
>>>>>>>>                                 <[email protected]
>>>>>>>>                                 <mailto:[email protected]>> wrote:
>>>>>>>>
>>>>>>>>                                     On 07/05/2016 06:47 PM,
>>>>>>>>                                     Pavan Yedavalli wrote:
>>>>>>>>>                                     Hi Marcus,
>>>>>>>>>
>>>>>>>>>                                     Thanks for the background.
>>>>>>>>>                                     That helps greatly. Having
>>>>>>>>>                                     said that, I am unclear
>>>>>>>>>                                     which commands
>>>>>>>>>                                     specifically tune the
>>>>>>>>>                                     radios, so I did the
>>>>>>>>>                                     following around the
>>>>>>>>>                                     frequency tuning (after
>>>>>>>>>                                     all of the time source,
>>>>>>>>>                                     gain, and antenna setting
>>>>>>>>>                                     code):
>>>>>>>>>
>>>>>>>>>                                             addr_string =
>>>>>>>>>                                     
>>>>>>>>> "addr0=192.168.10.3,addr1=192.168.10.4"
>>>>>>>>>                                            
>>>>>>>>>                                     self.uhd_usrp_sink_0_0 =
>>>>>>>>>                                     uhd.usrp_sink(
>>>>>>>>>                                                
>>>>>>>>>                                     ",".join((addr_string, "")),
>>>>>>>>>                                                 uhd.stream_args(
>>>>>>>>>                                                    
>>>>>>>>>                                     cpu_format="fc32",
>>>>>>>>>                                                    
>>>>>>>>>                                     channels=range(2),
>>>>>>>>>                                                 ),
>>>>>>>>>                                             )
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_clock_source("external",
>>>>>>>>>                                     0)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_time_source("external",
>>>>>>>>>                                     0)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_clock_source("mimo",
>>>>>>>>>                                     1)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_time_source("mimo",
>>>>>>>>>                                     1)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_samp_rate(samp_rate)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_gain(31.5,
>>>>>>>>>                                     0)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_gain(31.5,
>>>>>>>>>                                     1)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_antenna("TX/RX",
>>>>>>>>>                                     0)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_antenna("TX/RX",
>>>>>>>>>                                     1)
>>>>>>>>>                                            
>>>>>>>>>                                     self.analog_sig_source_x_0_1
>>>>>>>>>                                     =
>>>>>>>>>                                     analog.sig_source_c(samp_rate,
>>>>>>>>>                                     analog.GR_CONST_WAVE,
>>>>>>>>>                                     10000, 1, 0)
>>>>>>>>>                                            
>>>>>>>>>                                     self.analog_sig_source_x_0_0_0
>>>>>>>>>                                     =
>>>>>>>>>                                     analog.sig_source_c(samp_rate,
>>>>>>>>>                                     analog.GR_CONST_WAVE,
>>>>>>>>>                                     10000, 1, 0)
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                                     *       
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_time_unknown_pps(uhd.time_spec())
>>>>>>>>>                                             now =
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.get_time_now()
>>>>>>>>>                                             start_time = now +
>>>>>>>>>                                     uhd.time_spec(.5)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_command_time(start_time)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_center_freq(915000000,
>>>>>>>>>                                     0)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.set_center_freq(915000000,
>>>>>>>>>                                     1)
>>>>>>>>>                                            
>>>>>>>>>                                     
>>>>>>>>> self.uhd_usrp_sink_0_0.clear_command_time()*
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                                     However, when running it,
>>>>>>>>>                                     this does not appear to
>>>>>>>>>                                     produce a constant offset
>>>>>>>>>                                     either, but I'm not sure
>>>>>>>>>                                     whether this is the
>>>>>>>>>                                     correct code to wrap
>>>>>>>>>                                     around. Please keep me
>>>>>>>>>                                     posted. Thanks.
>>>>>>>>>
>>>>>>>>>                                     On Tue, Jul 5, 2016 at
>>>>>>>>>                                     12:49 PM,
>>>>>>>>>                                     <[email protected]
>>>>>>>>>                                     <mailto:[email protected]>>
>>>>>>>>>                                     wrote:
>>>>>>>>>
>>>>>>>>>                                         That is precisely what
>>>>>>>>>                                         I'm saying, and
>>>>>>>>>                                         precisely what
>>>>>>>>>                                         timed-commands for
>>>>>>>>>                                         tuning were invented. 
>>>>>>>>>                                         On certain hardware,
>>>>>>>>>                                         after the tune is
>>>>>>>>>                                         complete, a
>>>>>>>>>                                         phase-reset pulse is
>>>>>>>>>                                         sent by the FPGA. The
>>>>>>>>>                                         only way for THAT to
>>>>>>>>>                                         have the desired
>>>>>>>>>                                         effect is to make sure
>>>>>>>>>                                         that the phase-reset
>>>>>>>>>                                         pulse happens at the
>>>>>>>>>                                         same instant.
>>>>>>>>>
>>>>>>>>>                                         Modern synthesizers
>>>>>>>>>                                         use a technique called
>>>>>>>>>                                         fractional-N
>>>>>>>>>                                         synthesis.  One of the
>>>>>>>>>                                         side effects of this
>>>>>>>>>                                         is that you can't
>>>>>>>>>                                         predict where the LO
>>>>>>>>>                                         will "lock" with
>>>>>>>>>                                         respect to the
>>>>>>>>>                                         reference clock. So,
>>>>>>>>>                                         any two PLL
>>>>>>>>>                                         synthesizers, even
>>>>>>>>>                                         when feed an identical
>>>>>>>>>                                         reference clock, will
>>>>>>>>>                                         not have the same
>>>>>>>>>                                         phase offset with
>>>>>>>>>                                         respect to one
>>>>>>>>>                                         another.  It's the
>>>>>>>>>                                         "physics" of
>>>>>>>>>                                         fractional-N PLL
>>>>>>>>>                                         synthesis.
>>>>>>>>>
>>>>>>>>>                                         SO, if you're using
>>>>>>>>>                                         GRC to generate you
>>>>>>>>>                                         flows, you'll have to
>>>>>>>>>                                         modify the generated
>>>>>>>>>                                         code, and wrap
>>>>>>>>>                                         
>>>>>>>>> set_command_time()/clear_command_time()
>>>>>>>>>                                         around the place in
>>>>>>>>>                                         the code where it
>>>>>>>>>                                         tunes the radios.
>>>>>>>>>
>>>>>>>>>                                         Clearly, if this
>>>>>>>>>                                         depends on TIME, then
>>>>>>>>>                                         all radios involved
>>>>>>>>>                                         need to agree on the
>>>>>>>>>                                         current time, to high
>>>>>>>>>                                         precision, hence the
>>>>>>>>>                                         related requirement
>>>>>>>>>                                         for
>>>>>>>>>                                         set_time_unknown_pps(),
>>>>>>>>>                                         which uses the 1PPS
>>>>>>>>>                                         signal to trigger
>>>>>>>>>                                         loading of the
>>>>>>>>>                                         time-of-day clocks on
>>>>>>>>>                                         each USRP in the
>>>>>>>>>                                         multi_usrp object.
>>>>>>>>>
>>>>>>>>>                                          
>>>>>>>>>
>>>>>>>>>                                          
>>>>>>>>>
>>>>>>>>>                                          
>>>>>>>>>
>>>>>>>>>                                          
>>>>>>>>>
>>>>>>>>>                                         On 2016-07-05 15:41,
>>>>>>>>>                                         Pavan Srikrishna
>>>>>>>>>                                         Yedavalli wrote:
>>>>>>>>>
>>>>>>>>>                                             I am using USRP
>>>>>>>>>                                             N210 with SBX
>>>>>>>>>                                             daughterboards.
>>>>>>>>>                                             All devices are
>>>>>>>>>                                             connected to the
>>>>>>>>>                                             octoclock ref and
>>>>>>>>>                                             octoclock PPS. It
>>>>>>>>>                                             would be nice to
>>>>>>>>>                                             get phase
>>>>>>>>>                                             alignment, but
>>>>>>>>>                                             mere
>>>>>>>>>                                             coherence-with-an-offset
>>>>>>>>>                                             is sufficient if
>>>>>>>>>                                             that offset stays
>>>>>>>>>                                             constant across
>>>>>>>>>                                             different runs of
>>>>>>>>>                                             the
>>>>>>>>>                                             file/flowgraph.
>>>>>>>>>                                             Are you saying
>>>>>>>>>                                             that that offset
>>>>>>>>>                                             cannot be constant
>>>>>>>>>                                             due to the
>>>>>>>>>                                             randomness of the
>>>>>>>>>                                             LO phase offset at
>>>>>>>>>                                             each run? Thanks
>>>>>>>>>                                             again.
>>>>>>>>>
>>>>>>>>>                                              
>>>>>>>>>                                             
>>>>>>>>> _____________________________
>>>>>>>>>                                             From:
>>>>>>>>>                                             [email protected]
>>>>>>>>>                                             <mailto:[email protected]>
>>>>>>>>>                                             Sent: Tuesday,
>>>>>>>>>                                             July 5, 2016 12:35 PM
>>>>>>>>>                                             Subject: Re:
>>>>>>>>>                                             [Discuss-gnuradio]
>>>>>>>>>                                             random phase
>>>>>>>>>                                             offset constantly
>>>>>>>>>                                             changing with
>>>>>>>>>                                             octoclock setup
>>>>>>>>>                                             To: Pavan
>>>>>>>>>                                             Yedavalli
>>>>>>>>>                                             <[email protected]
>>>>>>>>>                                             
>>>>>>>>> <mailto:[email protected]>>
>>>>>>>>>                                             Cc:
>>>>>>>>>                                             Discuss-gnuradio
>>>>>>>>>                                             
>>>>>>>>> <[email protected]
>>>>>>>>>                                             
>>>>>>>>> <mailto:[email protected]>>,
>>>>>>>>>                                             GNURadio
>>>>>>>>>                                             Discussion List
>>>>>>>>>                                             <[email protected]
>>>>>>>>>                                             
>>>>>>>>> <mailto:[email protected]>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                                             WHat specific
>>>>>>>>>                                             hardware line-up
>>>>>>>>>                                             do you have?
>>>>>>>>>
>>>>>>>>>                                             You have to use
>>>>>>>>>                                             set_time_unknown_pps(),
>>>>>>>>>                                             but also, if you
>>>>>>>>>                                             want phase
>>>>>>>>>                                             alignment (as
>>>>>>>>>                                             opposed to mere
>>>>>>>>>                                             coherence-with-an-offset),
>>>>>>>>>                                             you need to use
>>>>>>>>>                                             timed tuning
>>>>>>>>>                                             commands across
>>>>>>>>>                                             your systems. This
>>>>>>>>>                                             will result in
>>>>>>>>>                                             zero relative
>>>>>>>>>                                             phase offset
>>>>>>>>>                                             between boards, if
>>>>>>>>>                                             you're using SBX
>>>>>>>>>                                             or UBX (on the
>>>>>>>>>                                             X310).  Note that
>>>>>>>>>                                             this is phase
>>>>>>>>>                                             between the
>>>>>>>>>                                             boards, there's no
>>>>>>>>>                                             way to make
>>>>>>>>>                                             certain the the LO
>>>>>>>>>                                             phase has a
>>>>>>>>>                                             predictable offset
>>>>>>>>>                                             with respect to
>>>>>>>>>                                             external received
>>>>>>>>>                                             signals, only that
>>>>>>>>>                                             the two LO phases
>>>>>>>>>                                             agree.
>>>>>>>>>
>>>>>>>>>                                              
>>>>>>>>>
>>>>>>>>>                                              
>>>>>>>>>
>>>>>>>>>                                              
>>>>>>>>>
>>>>>>>>>                                             On 2016-07-05
>>>>>>>>>                                             15:26, Pavan
>>>>>>>>>                                             Yedavalli wrote:
>>>>>>>>>
>>>>>>>>>                                                 Hi,
>>>>>>>>>                                                  
>>>>>>>>>                                                 Despite all of
>>>>>>>>>                                                 my boards
>>>>>>>>>                                                 being
>>>>>>>>>                                                 connected via
>>>>>>>>>                                                 the Octoclock
>>>>>>>>>                                                 (ref and pps),
>>>>>>>>>                                                 I am
>>>>>>>>>                                                 constantly
>>>>>>>>>                                                 getting
>>>>>>>>>                                                 different
>>>>>>>>>                                                 phase offsets
>>>>>>>>>                                                 every time I
>>>>>>>>>                                                 run a gnuradio
>>>>>>>>>                                                 flowgraph (or
>>>>>>>>>                                                 python file).
>>>>>>>>>                                                  
>>>>>>>>>                                                 I am not sure
>>>>>>>>>                                                 why this is
>>>>>>>>>                                                 happening, but
>>>>>>>>>                                                 I do know that
>>>>>>>>>                                                 I need to call
>>>>>>>>>                                                 one of the
>>>>>>>>>                                                 functions,
>>>>>>>>>                                                 set_time_now()
>>>>>>>>>                                                 and/or
>>>>>>>>>                                                 
>>>>>>>>> set_time_unknown_pps(),
>>>>>>>>>                                                 to make sure
>>>>>>>>>                                                 all of them
>>>>>>>>>                                                 are synced.
>>>>>>>>>                                                 Which one am I
>>>>>>>>>                                                 supposed to
>>>>>>>>>                                                 call? I have
>>>>>>>>>                                                 been calling
>>>>>>>>>                                                 
>>>>>>>>> set_time_unknown_pps(),
>>>>>>>>>                                                 but I am
>>>>>>>>>                                                 getting the
>>>>>>>>>                                                 above/below
>>>>>>>>>                                                 problem with
>>>>>>>>>                                                 that, so maybe
>>>>>>>>>                                                 set_time_now()
>>>>>>>>>                                                 could be correct?
>>>>>>>>>                                                  
>>>>>>>>>                                                 In general, I
>>>>>>>>>                                                 don't
>>>>>>>>>                                                 understand why
>>>>>>>>>                                                 I continually
>>>>>>>>>                                                 get a
>>>>>>>>>                                                 different
>>>>>>>>>                                                 random phase
>>>>>>>>>                                                 offset of all
>>>>>>>>>                                                 of the radios
>>>>>>>>>                                                 after every
>>>>>>>>>                                                 new flowgraph
>>>>>>>>>                                                 run. Shouldn't
>>>>>>>>>                                                 this offset be
>>>>>>>>>                                                 the same if I
>>>>>>>>>                                                 continue to
>>>>>>>>>                                                 transmit at
>>>>>>>>>                                                 the same
>>>>>>>>>                                                 frequency?
>>>>>>>>>                                                 Would one of
>>>>>>>>>                                                 the above
>>>>>>>>>                                                 functions fix
>>>>>>>>>                                                 that?
>>>>>>>>>                                                  
>>>>>>>>>                                                 Hopefully that
>>>>>>>>>                                                 is clear.
>>>>>>>>>                                                 Thank you so
>>>>>>>>>                                                 much for the help.
>>>>>>>>>                                                  
>>>>>>>>>                                                 -- 
>>>>>>>>>                                                 Pavan
>>>>>>>>>
>>>>>>>>>                                                 
>>>>>>>>> _______________________________________________
>>>>>>>>>                                                 Discuss-gnuradio
>>>>>>>>>                                                 mailing list
>>>>>>>>>                                                 
>>>>>>>>> [email protected]
>>>>>>>>>                                                 
>>>>>>>>> <mailto:[email protected]>
>>>>>>>>>                                                 
>>>>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                                     -- 
>>>>>>>>>                                     Pavan
>>>>>>>>                                     How are you measuring the
>>>>>>>>                                     phase-offset between the
>>>>>>>>                                     two sinks?
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>                                 -- 
>>>>>>>>                                 Pavan
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>                             -- 
>>>>>>>                             Pavan
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>                         -- 
>>>>>>                         Pavan
>>>>>
>>>>>
>>>>>
>>>>>                      
>>>>>                     -- 
>>>>>                     Pavan
>>>>
>>>>
>>>>
>>>>
>>>>                 -- 
>>>>                 Pavan
>>>
>>>
>>>
>>>              
>>>             -- 
>>>             Pavan
>>
>>
>>
>>
>>         -- 
>>         Pavan
>
>
>
>
>     -- 
>     Pavan
>
>     _______________________________________________
>     Discuss-gnuradio mailing list
>     [email protected] <mailto:[email protected]>
>     https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> [email protected]
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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