Leo Bodnar questions- Mini Precision GPS Reference Clock and  review of Chinese  - Page 1
Forum section: electronics / testgear

author: minsik
author_rank: Contributor
timestamp: January 21, 2024, 02:36:53 am
content: Hi. One on the way but cant find these answers.1) can the ublox u-centre work with this device or is all configuration limits to the Leo configuration tool which must be fixed at supply?2) Does unit output NMEA codes for use with external measuring or logging software?3) if yes? what software will work or monitor the data?PS: recently attained nerd status with getting interested in frequency timing by the initial purchase of a LOW quality ebay unit, GPSCSG GPS (trained) not disiplined, signal generator which has the std SI5351 output.Yes it does work (within the initial limit of me knowing nothing, i now know slightly more than nothing!)This unit has very bad assembly and operation (in my opinion)! (discovered in 24hrs since receiving!)1) SMA sockets all loose and badly placed and soldered. Of 5 connections on each sma socket ie two top mount points, two bottom mount points and a centre pin, only 2 were stuck! On both sockets! The face of SMA was discovered to be set back into the pcb too far so no way could be tightened up onto the back panel (which is nice and strong by the way) Required unsolder and reposition back out from the board by 2-3mm and then solder all points. This allows the SMA nuts and washers to tighten onto the back plate and fit correctly. 1 problem fixed.2) NO electro caps Anywhere in the cct. Very small values on pcb do not seem to be adequate filtering to me! (when my cap kit arrives will look at adding some to the two 3.2V regulator outputs for the Si5351 and the Atmel 328 SMD cpu.3) Display corrupts VERY easily (or is this the Atmel?). Just leaving unit sit and come back 1hr later display has locked up with gobbledygook! But still generating correct output. Only way to reset is power cycle. Also by unpluging the output cable and replug display locks up or corrupts with random stuff on the display. Unplug and plug the USB-C cable also might cause display to lock up or no output.4) Output May work! Change the output frequency and it may cause NO output at all, only cure = power cycle. Ie set on 10Mhz and change to 1Mhz, or vice versa.5) Fstab NEVER seen at zero and therefore as I understand it, will never store the correction value to use at next power up. 10Mhz Fstab is best at -500Hz. 200Mhz is best at -6000.0Hz.Only information i can find related is when Fstab is <0.1hz for a period of time = correct locking and control it will store the values for quicker startup next time. These Fstab values jump back and forth, always negative and never stable!6) Quite a bit of jitter is evident (newbie and using FA-3 OCXO frequency counter.) Just using the min/max/av/deviation measurement of the FA-3.Yet the unit does attain 6-9 satellite's and seems to work fast and correctly, Pll lock (as indicated by star symbol at end of top line) appears after approx 80 seconds. TCXO internal seems quite close on power up and doesn't change too much when lock is attained.thanks any guidance or infomation.PS someone said 5Mhz needed for Marconi 2955 but all i can see for this Marconi 2955R is that it needs 1MHz. So far not using the GPSCSG as external reference just measuring on iput with internal OCXO. that was checked an minor adjusted against some late calibrated RS gear. FSW and an ETL.Minsik.Australia.

author: SCSKITS
author_rank: Regular Contributor
timestamp: January 22, 2024, 04:09:52 pm
content: I had access to a BODNAR unit for a few weeks for comparison as part of a GPSDO project.The USB is for the BODNAR control program, not the UBLOX control program.I did not have the time or the means to try any 3rd party USB comm programs to see if messages were available.The unit I had used a U-BLOX MAX-M8Q conditioned by a SI5328C.The SI-5328C is a 5 to 6 GHz PLL/jitter correction IC with a low loop bandwidth that can be programmed from 0.05 to 6 Hz.The other SkyWorks devices all have higher loop bandwidths that can not correct the GPS jitter.Initial testing indicated that the output should be acceptable for most users.ed

author: minsik
author_rank: Contributor
timestamp: January 23, 2024, 12:27:06 pm
content: As far as I can see yes thats the unit and parts you mention.You cleared a couple of questions so thanks.appreciated, but maybe from tomorrow if delivery happens I will then know even more.Minsik thanks you. .