| Electronics > Projects, Designs, and Technical Stuff |
| GPSDO: PLL or MCU controlled? |
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| Theboel:
Hi All, Could I suggest something ? 1. You need to think very serious about how to check Your GPSDO design, if You want You can use TAPR TIC for measurement. https://tapr.org/kits_ticc.html This is not a toy believe me only very few "thing" has same capabilities or better than this board but with Thousand USD price tag. but if You like adventure You can try this : https://www.ebay.co.uk/itm/FA1-USB-simple-High-Precision-Virtual-Frequency-Counter-Frequency-Analyzer/173883937521?hash=item287c4a52f1:g:hoMAAOSwEbxcwZQ4 or this https://www.ebay.co.uk/itm/FSA3011-OCXO-GPSDO-Atom-Clock-Frequency-stability-Analyzer/254258571356?hash=item3b32fde85c:g:6bUAAOSw7CBc~PXi 2. GPSDO for me has 3 ingredient : a. Oscillator You want to discipline, almost anything You can discipline. OCXO,TCXO, Rb, even active Hidrogen maser b. GPS module use to generate clock use for discipline the oscillator, You can use any GPS module with 1PPS out from "fake ublox up to very high price geodetic GPS receiver" c. Control unit, You can Go to TIC+MCU, etc 3. If You want to just have GPSDO with average performance I think nothing simpler than JRmiller design http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm but if You want or can more bell and whistle You can try Lars design https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/ in case You want MCU without to many complicated You can look at leo bodnar design https://www.eevblog.com/forum/metrology/leo-bodnar-mini-precision-gps-reference-clock-teardown/msg1398826/#msg1398826 if You ask me I will use MCU with TIC like lars design with some additional sauce ;) ;) ;) |
| fourfathom:
--- Quote from: edigi on August 02, 2019, 03:23:59 pm ---One quick note: For the interpolating part highly deterministic delay is needed that is for that part CPLD is a must and FPGA won't cut (not only that, CPLDs with FPGA like internal architecture won't cut either). --- End quote --- What kind of specs are you looking for here? I'm surprised that you can't get these deterministic delays with a CPLD, since 100MHz (and faster) internal clocking is pretty typical and with clocked outputs the delay variation will be within a couple of nanoseconds. |
| Johnny B Good:
--- Quote from: Illusionist on August 03, 2019, 10:32:43 am --- --- Quote from: Johnny B Good on August 02, 2019, 11:43:08 pm --- I've just placed an order for 50x SOP8OP8 TSSOP8 SMD To DIP8 Adapter 0.65/1.27mm PCB Board F6T4 as a result of checking out ebay for those LEA-6Ts. At just £1.06 delivered, it was a bargain I just couldn't resist, --- End quote --- Same here, same price! Couldn't resist that. More importantly, the seller in France that I got my NEO-M8T from has more: https://www.ebay.co.uk/itm/Ublox-NEO-M8T-0-IC-GNSS-Receiver-GPS-GLONASS-BeiDou-Galileo/193014081445?hash=item2cf08927a5:g:3YoAAOSwt91cxbn8 As far as I can tell, these are the genuine article. Mine are working well and I flashed them with the latest firmware. The main differences between the NEO and LEA are the NEO does not have an internal bias-t for antenna power, but instead has a second internal LNA and a filtered power output for feeding into an external bias-t. That's what I did. I designed a simple development circuit and had the PCBs made at JLC - I still have a couple spare... --- End quote --- Unfortunately, I'm only at the veroboard and pre-assembled RasPi / Arduino GPS module level of construction (I've no plans to solder bare u-Blox modules onto custom boards right now). Mind you, until I took a look at u-blox's data sheet on the 8T series to check the pin count, I'd briefly entertained the notion of replacing the M8N chip (24 pin) on the original module board that had suffered a jolt of 12 volt up its backside (the now destroyed PPS pin) with an 8T until I'd seen the pin out count mismatch (28 pins). As much as I hate dealing with anyone shipping via Hong Kong these days, I just might go for one of those drone navigation modules after all if I still can't track down a reasonably priced less long distance source over the next few months. At least the pin count was correct on the modules soldered to the navigation module's pcb in the more revealing pictures in the link I'd posted and I do know how to extract the ceramic patch antenna to solder an SMA antenna socket pigtail to the board and where to access the PPS and the serial port connections to pervert one of them into doing duty as master to the OCXO in my current project's box of tricks. As I mentioned in another thread, "There's more than one way to skin a cat." :) For some reason, I'd been reminded about those cheap chinese Hakko T12 soldering station clones (from a posting in the FY6600 thread way back in November last year - where else? ::)) and had finally taken the hint to look more deeply into the subject of modern soldering station technology, in particular of the (what else? - I own an Fy6600 for goodness' sake!) cheap kind. So, now I'm in the market for help and advice on the matter of soldering station technology and since you're working on smd circuit boards, I thought you might have some useful advice to offer in this matter, if I might be so cheeky as to prevail upon your kindness (even if it's just a link to a blog or discussion thread to save you the tedium of repeating what almost everyone else would have to say on the subject ::) ). I'd already come across a video tutorial on the business of building a Hakko T12 clone station from a kit of parts but it's obviously a year or more older (I couldn't date the tutorial but most of the links to sources of supply are 'dead' with redirects to possible alternatives). The first link redirected me to a selection of everything needed except the 24 volt 4 amp psu in the suggested parts list, leaving me the impression that there are many ways I can take a wrong turn in my quest to build a Hakko T12 clone setup on the cheap, hence my taking this opportunity to seek your advice on this aspect of the hobby of diy electronics project work. My modest collection of 15, 20 and 24 watt Antex soldering irons just aren't going to cut it with my more recent interest in electronic projects hence my "sudden" interest in modern soldering technology that's now seemingly within the financial grasp of the home hobbyist market. I realise it's a bit of an imposition to spring such a "left field" question 'out of the blue' on you like this but I figure the worst that could happen is to be told to take a hike and do my own 'homework', so worth the tiny risk of being sent off with a flea in my ear in putting that adage of "Ask, and it shall be told" to the test. :) BTW, getting back on topic, I've managed to open the holes up required to fit a barrel jack onto the back edge of the veroboard in my GPSDO. I haven't got as far as soldering anything onto the veroboard just yet; there are still a few details to be sorted out before then. Still, I have cut a few tracks to match where I've placed the major components as shown in the attached images, so at least part of the final layout is now decided (if not quite set in stone - veroboard being veroboard, there's still opportunity to make last minute changes if deemed essential). JBG |
| Vgkid:
Look into csgshop.com they sell a ton of ublox modules. I wish shipping was cheaper to usa. Keeps me from buying stuff. |
| Johnny B Good:
--- Quote from: Vgkid on August 04, 2019, 02:07:16 pm ---Look into csgshop.com they sell a ton of ublox modules. I wish shipping was cheaper to usa. Keeps me from buying stuff. --- End quote --- I presume you were trying to remind of the exorbitant pricing of u-blox product in the USA and how lucky I am to be able to find Chinese bargains? :-// JBG |
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