Mastering Precision: 10MHz Reference Testing & Analysis (TM4313 GPSDO)

[@Runco990]

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". 👍

[@solodolo6018]

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.

[@bayareapianist]

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.

[@mikesradiorepair]

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.

[@ZenwizardStudios]

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.

[@jspencerg]

No mention of your Leo Bodnar unit or how it compares to this unit. ?

[@ZenwizardStudios]

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.

[@jspencerg]

@@ZenwizardStudios I have connected the one- port Bodnar unit to a $65 amplifier/ splitter I found on epay. It seems to work very well.

[@pbnjimages294]

is there software to talk to the unit with the usb port?

[@nreitcheck]

You should test the holdover as well. Sometimes you loose GPS for solar flares and weather events, how well does it hold frequency.

[@ZenwizardStudios]

I can defiantly add that to the Spread Sheet.

[@scrook1027]

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.

[@ZenwizardStudios]

From what I saw on the instrumentation the slow flash is when the unit is locked and stable.

[@scrook1027]

@@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.

[@t1d100]

👍👍👍

[@jasontang6725]

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.

[@ZenwizardStudios]

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

[@nickloughrey9841]

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 .

[@ZenwizardStudios]

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.