Trimble Thunderbolt GPS Disciplined Oscillator

[Bryan]

All:

Trying to find as much info as I can on putting together a GPSDO, and the Trimble thunderbolt keeps coming up as a good solution for a 10Mhz frequency standard. I do see them come up every once in awhile on FleaBay. Some have older firmwares from 1.90 to 3.00. Is there a firmware that I need to look for or stay away from. Will something as old as 1.90 be fine. Can the firmware be upgraded by the end user?

[true]

I have boards with older firmware than that - you generally want to stay above 1.86 IIRC. I have a 1.86 and a 1.88 board and both run fine. I'm not sure if they are user upgradable, and if they are, I don't know where to find the firmware.

[Dr. Frank]

Hi,
this has been discussed on time-nuts intensively, a few years ago already.
Please check this site for details.

As far as I remember, the SW version was not that important compared to the version of the internal oscillator.

It is important to get the Trimble OCXO (silver box) instead of that much less well performing VCXO / piezo resonator (?) version (red label).
I've got F.W. 2.22 with OCXO, which is very good. See photo of my spare unit, and time-nuts or various other private sites (http://www.ke5fx.com/tbolt.htm) about that.

Frank

P.S.: Needless to say, that you also need the connection cable and a PSU delivering all the necessary supply voltages, and a GPS antenna.
Chinese sellers like l.fluke (very reliable) then sold complete sets for about 170€/$, or so.

But I think they are sold out since a long time.

P.P.S.: My active unit is running F.W. 3.00 (2002), which was the best and last one.
I don't remember, but maybe l.Fluke already programmed the spare unit also with FW 3.00.
It was quite difficult or impossible to get this binary from Trimble.
Anyhow, the 'Trimble Visual Timing Studio' has an option for the firmware.
Therefore, it may be possible to upgrade older boxes also.

[Bryan]

Funny you mention the seller fluke.l. Have heard others mention he is a good seller. I did look up his latest items and he does have some Trimble boards, but they are different then yours and others I have seem. Much larger in size and look like a custom product for Nortel Networks. Just wonder about the comparability as I am sure any written material on the operation of the board  would be non existence. As well it looks like they have a custom power supply on board and require a 48V source. I wonder if it is a better product than the classic Thunderbolt though.

http://www.ebay.com/itm/TRIMBLE-10mhz-GPS-Disciplined-oscillator-board-for-Frequency-Counter-last-8-psc-/291054324150?pt=LH_DefaultDomain_0&hash=item43c43089b6

[true]

It is comparable to the Thunderbolt, and can use similar (same?) tboltmon to work with it.

I have a couple of these too and they work alright. As Dr. Frank wrote, keep a lookout for the oscillator in use. The ones that eBay seller is selling aren't the best versions of the Trimble OCXO but mine work well. Those boards will work well enough for cheap GPSDO or clock purposes.

[VK5RC]

The power supply is different than the t-bolt (actually easier as single dc supply, I recall? 50v dc)  mine took a while to lock (15mins),  but has a good  double oven oxco. 

[bingo600]

Whoaa

The Tbolt prices have skyrocketed , i think i payed around $110 for ea. my 3 units.

As much as i love Lady Heather , i'd consider a Z3805 w. a 18011 OCXO.
http://www.ebay.com/itm/HP-Z3805A-10811-DOCXO-GPS-Frequency-Time-Receiver-10-MHz-1PPS-/251527198011

I have a Z3801 that also runs excellent , here it shows a predicted uncertainty of 3.2 us for the first 24/hr in holdover mode.




/Bingo

[Bryan]

The power supply is different than the t-bolt (actually easier as single dc supply, I recall? 50v dc)  mine took a while to lock (15mins),  but has a good  double oven oxco.

Would you recommend going with that particular board or trying to source one of the other versions. the ones offered for sale look like they have a  good OCXO, but the board is almost a foot long.!!

[VK5RC]

I would try to get a good t-bolt or z380x witha good oven,  the nortel special is so big,  I think mine is at the edge of its life /adjustment,  I have been too lazy to try and trim it.  The time nut guys and all the knowledge and software seem to be  all around t-bolt or HP z380xs.

[Fraser]

+1 for the thunderbolt units. I have a pair running well for the last 4 years. They are nice and compact and fit in a bench friendly sized case with ease. I run mine from Ex Cell phone tower GPS antennas with a stated 38dB gain. I believe the thunderbolts prefer an antenna with decent gain.

Just after I bought my thunderbolts one of the sellers (fluke.l ?) started offering a neat little LCD display that connected to the serial port. The display provided the units lock status etc. It was a Chines conversion of a consumer in car audio product. The display microprocessor was programmed with code written by a fellow thunderbolt owner. You can DIY such a unit using information available on the internet. Some Googling should find it.

My Thunderbolt GPDSO's cost me less than $100 each and they are both running the V3 firmware and have a decent OCXO installed. The later firmware's tend to indicate a younger thunderbolt unit and that can be an advantage when it comes to OCXO aging. The LCD display units were cheap as chips at around $15 IIRC. The donor display modules were available very cheaply indeed at that time due to the main I.C.E unit becoming obsolete. It was 'Monster' branded I believe.

All this from distant memory so E&OE 

I also own a lovely pair of Quartzlock 2A off air frequency references (10Mhz, 5MHz, 1 MHz & Raw 198kHz carrier). Much more convenient than my GPSDO when mobile, and they give very good accuracy for my frequency counter etc. I just bought the second unit for around GBP100. They are well  worth the money if you are in an area that can receive BBC Radio 4 on 198kHz.

Aurora

[Richard Head]

Aurora

I run mine from Ex Cell phone tower GPS antennas with a stated 38dB gain.

For GPS reception you don't want a high gain antenna because it means it's directional. You idealy want a circularly polarised omnidirectional antenna like a QFH.
However, if it works who cares I suppose.

[Bryan]

Anybody used or have any comments on the FEI PicoSync. See them offered every once in a while.

[Bryan]

Looks like those larger Trimble boards are similar to this

http://www.realhamradio.com/GPS_Trimble_Receiver.htm

[rf-loop]

Aurora

I run mine from Ex Cell phone tower GPS antennas with a stated 38dB gain.

For GPS reception you don't want a high gain antenna because it means it's directional. You idealy want a circularly polarised omnidirectional antenna like a QFH.
However, if it works who cares I suppose.

This gain is not passive antenna element gain due to narrow radiation sector angle. My opinion is that it is total gain including antenna module internal amplifier.   (but I have experience only about under 100 GPS (active)antennas and under 10 different models)  With omnidirectional passive antenna... no one do not want even try with Trimble or Z3801. 
-----------------------

These Nortel boards are around as good as Trimble Thunderbolt (some may have even better OCXO).
 Z3801 is far over Trimble Tb  if look its frequency stability, mainly due to its extremely good OCXO.  TB can be also good but it need know how to adjust it. Default parameters are more or less bad for frequency reference use.  These parameters are compromize for new units and for keep time in higher priority than frequency stability. (discipline for as stabile freq as possible is different).  Also warning, monigtor programs do not know real, they know what it think about itself!  (short time stability)  Of course ~8h or more long average is very good. Even if look Lheather short time ppb error it do not tell truth, it tell what TB know about itself.  Also TB's are individuals because internal OCXO's are different. My opinion is that perhaps best are these TB's where OCXO is made by Vectron. (can not see in top label because they use OEM from not only one manufacturer)

I have tested tens of TB's. There is (big) differencies between individual units if use factory defaults. Example OCXO discipline parameter Hz/V may be far away from right value.

New parameters can not easy find if user do not have good reference for accurate measure TB output.

For hours long average of course these do not matter so mmuch or nearly anything.

Poor temperature stability is one weakness of Thunderbolt.
Btw, I have never seen Trimble Thunderbolt with some other 10MHz oscillator than OCXO.

--------
About fluke.l
I can recommend, also I know him in real life in Guangzhou and not only with some business.

[VK5RC]

Testing any of these units gets REALLY expensive as you really need a reference 10x better,  ie hydrogen maser etc,  but you can have a great reference for the lab that would have been the envy of universities a decade or so ago for <$200. The time nuts archive is a great reference,  esp leap-second website.

[jpb]

I also own a lovely pair of Quartzlock 2A off air frequency references (10Mhz, 5MHz, 1 MHz & Raw 198kHz carrier). Much more convenient than my GPSDO when mobile, and they give very good accuracy for my frequency counter etc. I just bought the second unit for around GBP100. They are well  worth the money if you are in an area that can receive BBC Radio 4 on 198kHz.

Aurora

A few of these have come up recently and I wondered about bidding, but prices were approaching GPSDOs and I understand that the long wave broadcast by the BBC is dependent on ancient valves which are past their working life and won't be replaced if they go (at least according to Wikipedia). Additionally others have reported issues at different times of day. I'd still like to get one but by the time I do, the long wave broadcasts will probably have ceased!

In 2011 as part of the BBC cuts it was announced that there would be no re-investment in long wave which may mean an eventual end to BBC Radio 4 in this part of the radio spectrum.[3] It was later announced that the transmitter relies on a pair of metre-high glass valves that last between one and ten years. There were fewer than ten remaining in the world, and the corporation was not inclined to go to the expense of manufacturing new ones.

see

http://en.wikipedia.org/wiki/Droitwich_transmitting_station

[gxti]

For timing GPS antennas, the stated gain is for the amplifier. It's there to compensate for cable loss, not low signal, because the signal and noise both get amplified. Very handy if you're using a splitter.

[bingo600]

I'm using this 40dB  Maxrad Timing antenna
http://www.antenna.com/apg_products.cgi?id_num=11091

And an active 4-way splitter for GPS.
http://www.gpssource.com/products/gps-splitter/118

Right now i have a Tbolt , and the Z2801A on the set.
And hopefully soon my new toy will be connected : A SRS PRS10 Rubidium  from *bay , sync'ed to GPS via 1-PPS from a M12+T (from fluke.l) , as an extra i'm  using an AVR for reading the 1-pps correction out of the M12+T , and correcting the 1-PPS using a Dallas Delayline

Currently i'm building the PSU board for the M12+T , the Dallas delayline , and the Arduino Mega.
Then the Arduino will be used as 3-way serial interface , and for 1-pps correction.

It might take a little while , as i'm learning VHDL (beginner) , and have decided to implement all the "Glue logic" in a CPLD .....

/Bingo

Edit: My last two tbolts was newer models from a US seller , they had tthe new temp. sensor chip in them.
So i decided to change the temp sensors to the older revision , to utilize the high res temp sensing on those.

[Fraser]

That looks just like my antenna 

A key feature of these 'ice-cream cone' antennas is that they are a QFH feeding a high performance amplifier via an equally high performance band-pass filter. They are designed to provide good low noise gain with excellent immunity to interference from signals outside the GPS band. They sit near the Cell antennas after all !

I have also bought a couple of ACE GA1575 antenna that resemble a hockey puck. These are 38dB gain but presumably use a patch antenna element and I am uncertain whether they have a band-pass filter inside. They cost ne GBP15 each last week from a Chinese seller.

Whilst I accept that the high gain amplifier amplified noise as well as signal and so cannot improve S/N ratio, some of the GPSDO's are a tad deaf and need quite a high signal level at the antenna input for reliable operation. the filtered antennas help avoid the amplification of adjacent signals as well and so avoid overloading the receiver front end. The spec for the Trimble is IIRC a 38dB antenna in order to compensate for the losses in the coaxial feed down the tower to the electronics rack.

Aurora

[Bryan]

Something I never considers is whether a GPS disciplined oscillator will even work for me .  I live in a condo with a northern exposure 49°15?N  123°06 is my approx coordinates. If I hang my cellphone out the balcony window with a GPS program it reports 3 satellites found.

[jpb]

Something I never considers is whether a GPS disciplined oscillator will even work for me .  I live in a condo with a northern exposure 49°15?N  123°06 is my approx coordinates. If I hang my cellphone out the balcony window with a GPS program it reports 3 satellites found.

For timing mode, if the position is known, frequency can be obtained from just one satellite (from the Ublox Lea 6T timing application note) :

If the position is known, the receiver can provide an accurate time solution by tracking only one satellite

But you'd need a timing GPS module that allows you to enter the co-ordinates rather than surveying them.

I think something like the Ublox Lea-6T would do it and it also will directly output (with some jitter) high frequencies such as 8MHz (the clock is 48MHz so 8MHz has a lot less jitter than 10MHz).
By phase locking the output to a good OCXO you should be able to remove most of the jitter and get much better phase noise.

https://www.u-blox.com/images/downloads/Product_Docs/LEA-6_DataSheet_%28GPS.G6-HW-09004%29.pdf

Fixed Mode
In this mode, a fixed 3D position and known standard deviation is assumed and the timing features are
activated. Fixed Mode can either be activated directly by feeding pre
-
defined position coordinates (ECEF
-
Earth Ce
nter Earth Fixed format) or by performing a Survey
-
In.
In Fixed mode, the timing errors in the TIMEPULSE signal which otherwise result from positioning errors
are eliminated. Single
-
satellite operation is supported. For details, please refer to the
u
-
blox
6 Receiver
Description including Protocol Specification

[Fraser]

@Bryan,

If you bave a balcony and your phone GPS can see 3 satellites you should be just fine. The satellites are orbiting so as one leaves your LOS , another should pop into view maintaining the continuous coverage. I have often managed to achieve at least 3 satellites in view whilst placing my TomTom car GPS on a window cill that is North facing. Remember, GPS satellites are not geostationary in the Clarke Belt, so a Southern view (in the Northerm Hemisphere) is not essential    Worth having a look at the Wiki for GPS if you would like more info.

http://en.wikipedia.org/wiki/Global_Positioning_System

Aurora

[Bryan]

Thanks Aurora, that is good to know, probably better satellite reception with a proper antenna. Strictly want a 10Mhz reference standard so even if I can manage a lock for a couple hours I should be fine.

[edpalmer42]

Thanks Aurora, that is good to know, probably better satellite reception with a proper antenna. Strictly want a 10Mhz reference standard so even if I can manage a lock for a couple hours I should be fine.

You might want to consider a GPS disciplined Rubidium oscillator.  Most GPSDOs use an ovenized quartz oscillator, but if it turns out that you can only get a GPS lock intermittently, the Rubidium would give better performance.  Or use a Rubidium as your house reference and compare it to GPS occasionally.

Ed

[Dr. Frank]

Thanks Aurora, that is good to know, probably better satellite reception with a proper antenna. Strictly want a 10Mhz reference standard so even if I can manage a lock for a couple hours I should be fine.

You might want to consider a GPS disciplined Rubidium oscillator.  Most GPSDOs use an ovenized quartz oscillator, but if it turns out that you can only get a GPS lock intermittently, the Rubidium would give better performance.  Or use a Rubidium as your house reference and compare it to GPS occasionally.

Ed

No, to discipline an Rb clock by GPS is not good at all.. this would spoil the very good short and midterm stability by the GPS jitter.

The Rb itself is so stable, that it makes no sense to discipline it further, it's better to calibrate / compare it once in a month or once in a 3 months.

Most of GPSDO time bases, like the Thunderbolt or the ones from HP have a quite good Holdover logic, that means they learn how the OCXO behaves over time and over temperature changes, and if the GPS signal fails, the Holdover circuit corrects the OCXO by monitoring the temperature.

TB works quite stable in this Holdover mode, HP GPSDOs seems to be better, due to a more stable OCXO. For performance figures, see various time-nuts sites.

Much more important, if the antenna is located freely on the roof of the house, maybe +/- 60° free sight to the sky, you will see at least 3-4 satellites all the time , and therefore never loose GPS track, maybe for a few minutes in thunderstorms only.

Btw.: Initially, an exact determination of the antenna position (< 1m) is important.
TB & LH offer a 24/48/72h survey function for that.

Frank