Mastering Precision: 10MHz Reference Testing & Analysis (TM4313 GPSDO)
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- Опубліковано 8 тра 2024
- EEVblog forum link to the post containing the Excel Document - www.eevblog.com/forum/metrolo...
A huge thank you again for all that continue to Join us in the lab for repairs and alignments. The channel would not exist with out all of you so thank you again for dropping by.
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In this video we take a look at an offering from the great auction site in the sky for a GPSDO. I have been asked a few time what I think about GPS units and given that we have a lab available to us here and gear that can DO the testing It was time to get it going. So here is the first GPSDO that we are testing! I am starting to build a table for some stability references to aid in picking the GPSDO that is right for you!
** Repair exposes the Tech to mains electric and should only be done by trained personnel. Errors can be fatal. ** - Наука та технологія
It is arguably AMAZING what is now available to the "Hobbyist" Tech. I also have a Rubidium and GPSDO. Though I built my Rubidium oscillator at a time when ebay sellers haven't lost their minds yet.... the modules sold for $79 all day long. They are "good enough for me". 👍
I would buy the ones with LCDs to read the status. Whoever did the design tried to save a dollar on this one. I bought one from AliExpress and I'm very happy.
When my old HP GPS time and frequency reference receiver finally kicked the bucket I got a new Stanford Research Systems GPSDO and frequency counter with optional rubidium time base. Best of both worlds, GPS and rubidium. However, you could probably buy a rather large pile of those little GPSDO's for what I paid for the SRS one new. If I only worked on HF/VHF/UHF transceivers one of those little things would probably be fine. In my case I also work on SHF and EHF transceivers. A tiny error in the 10MHz reference to one of the EHF radios can cause a frequency error of hundreds if not thousands of Hertz error.
I have a similar set up here. I have a GPS unit steering a FS725. It is the same physics package but I do have have the associated frequency counter.
I just got a fleabay gpsdo and a name brand distribution amplifier this week and I am pumped to have a stable frequency standard! Its pretty awesome to see how close to spec my gear is without being calibrated in who knows how long.
👍👍👍
You should test the holdover as well. Sometimes you loose GPS for solar flares and weather events, how well does it hold frequency.
I can defiantly add that to the Spread Sheet.
No mention of your Leo Bodnar unit or how it compares to this unit. ?
That is a really good point I should do the same testing with the Leo. I do have one of his 2 port units that I could test.
@@ZenwizardStudios I have connected the one- port Bodnar unit to a $65 amplifier/ splitter I found on epay. It seems to work very well.
is there software to talk to the unit with the usb port?
I bought one of these, there is about zero info on them. I'm curious about the tracking led status. Initially the led flashed quite fast. After about a day it slowed to about one flash a second. Then it started to flash fast again. Does anyone know if this is normal. The antenna is outside and in the clear.
From what I saw on the instrumentation the slow flash is when the unit is locked and stable.
@@ZenwizardStudios Thanks. It took about 24hrs after I first pugged it in to slow flash. Just sitting there it started to fast flash and after about 2 days it is now slow flashing.
I wonder if there is something wrong with it.
Does your unit ever lock? Mine doesn't. Check the NMEA output from the USB serial port - you might be surprised to see it never locks. Without the GPS, it's just a glorified OCXO.
It seemed to based on the LED patterns as well as the stability. I have a active GPS antenna outside that is shared between my bench GPSDO, a 2 port Leo GPSDO, and Leo's GPS NTP server. All seem to lock quite well. Usually this is due to signal level at the patch antenna. I have had units struggle with the patch antenna at the bench especially because the lab is below ground
All very interesting as a hobby , but without having been authorised as a calibration lab and having all trhe associated paperwork like UKAS accreditation , in the uk .............. it is just that a hobby .
In this cases as this analysis was only on frequency this one is traceable back to NIST cesium through the GPS network as far as my understanding goes.
Buy a Cesium standard :) 🕰
Thought about it. Cs is about 10X the cost of Rb so I need to hang in the Rb world for a little while longer.