GPS Disciplined 10 MHz references

[VK5PJ]

On ebay, you can find these for around $340 aus, it includes the Thundebolt GPS module with 1pps and 10 MHz outputs, a Motorola Antenna, external PSU and a serial cable.

Now this may not be the bee's knees of GPS's but I hope it will provide me with a decent station reference for the COUNTER and SIG Gen.

-------------------------------------------------------- Ebay Add ------------------------------------------------------

For the Trimble Thunderbolt GPS Disciplined Clock
Please read below

For datasheet and more specifications, please visit: http://www.trimble.com/tmg_thunderbolt.shtml

Thunderbolt GPS Disciplined Clock
Precise GPS Clock for Wireless Infrastructure

The Thunderbolt™ GPS Disciplined Clock is Trimble’s latest offering for GPS synchronization devices targeting the wireless infrastructure. This fourth-generation GPS clock combines an 8-channel GPS receiver, control circuitry and a high-quality ovenized oscillator on a single board, providing increased integrity and reliability at a lower size and cost.

The GPS clock’s level of integration makes it a perfect solution for precise timing applications in the wireless industry.

Among its uses are synchronizing the E911 positioning infrastructure and maximizing bandwidth for wireless local loop.

The architecture is comparable to systems currently used to maintain the tough CDMA holdover specification. This makes the hunderbolt GPS clock a natural for a CDMA clock, the digital standard for cellular phones.

Trimble’s approach is unique. The Thunderbolt GPS Clock outputs a 10 MHz reference signal and a 1 PPS signal with an over-determined solution synchronized to GPS or UTC time. The 10 MHz reference accommodates applications requiring sub-microsecond timing.

A single microprocessor performs both the GPS navigation and oscillator disciplining functions.

The GPS receiver is driven directly by the 10 MHz output signal of the oscillator. This is calibrated against the incoming GPS signal, with the resulting clock and frequency measurements fed into the oscillator frequency control algorithm.

The T-RAIM (Time-Receiver Autonomous Integrity Monitor) algorithm is used to monitor satellites to ensure signal integrity.
Matching the Thunderbolt GPS Clock with Trimble’s Bullet™ antenna creates a system thatprovides reliable performance in hostile environments. The system can be easily calibrated for different cable lengths.

The high level of integration and volume production techniques make the Thunderbolt GPS Disciplined Clock an extremely cost-competitive timing solution for volume synchronization applications.

Key Features and Benefits
• Ovenized quartz oscillator provides clean 10 MHz (1 PPS) signal that maximizes bandwidth
• Combined GPS receiver and ovenized oscillator minimizes size and cost
• High volume manufacturing provides reliable low-cost products

PERFORMANCE SPECIFICATIONS
General: L1 frequency, CA/code (SPS), 8-channel continuous tracking receiver
Update rate: 1 Hz
PPS accuracy: UTC 20 nanoseconds (one sigma)
10 MHz accuracy: 1.16 x 10-12 (one day average)

Harmonic level :–40 dBc max
Spurious: –70 dBc max
Phase noise:
10 Hz –120 dBc/Hz
100 Hz –135 dBc/Hz
1 kHz –135 dBc/Hz
10 kHz –145 dBc/Hz
100 kHz –145 dBc/Hz
Holdover:
±1 microsecond over 2 hours with a maximum
±15°C temperature change
Some customers, such as CDMA manufacturers, have historically mandated tighter holdover requirements than specified on this datasheet. For
increased holdover performance, please contact your local Trimble representative.

10 MHz:
BNC connector. Waveform is sinusoidal +12.5 dBm ± 2.5 dBm into 50 ?

Serial interface:
RS-232 through a DB-9 connector

Serial protocol:
Trimble Standard Interface Protocol (TSIP) binary protocol @ 9600, 8-None-1

PERFORMANCE SPECIFICATIONS

General: L1 frequency, CA/code (SPS), 8-channel continuous tracking receiver
Update rate: 1 Hz
PPS accuracy: UTC 20 nanoseconds (one sigma)
10 MHz accuracy: 1.16 x 10-12 (one day average)
-------------------------------------------------------- Ebay Add ------------------------------------------------------

Next job is to connect it up and let the reference oscilator settle into sync (I hope)

I am not sure what others are using but this is quite small, see this page on the trimble site for more
info http://www.trimble.com/tmg_thunderbolt.shtml

When I have more info and some piccies, I will add to the thread... maybe even time to lock a few of the VHF rigs for summer?

[VK3HZ]

Hi Peter,

I posted the following to the VK-VHF list the other day, which may be of interest to readers of your posting:

---------------------------------------------------------------------------------------------------------------------------------------------

For those of you interested in locking your rigs, or if you're just looking for a good frequency reference, TAPR have just finished a group buy of the high-performance, OCXO-fitted Trimble Thunderbolt units at a very good price (about $A175 landed at current rates), and it looks very likely that more will become available.

Details are here: http://www.leapsecond.com/pages/tapr-tbolt/

To be eligible, you need to be a member of the Time-Nuts group:
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

An announcement will be made on the list when the next batch becomes available.

Regards,
Dave

[VK2XAX]

I have one of these and it works a treat.
I used a JayCar KC5418 PSU board modified for 12v and a toroid transformer to provide a nice clean supply for it and I found a Symmetricom antenna http://ngn.symmetricom.com/pdf/datasheets/ds-58532a.pdf on ebay for about $40

well worth the $

cheers

Tim

[VK5PJ]

After some looking I found the URL for the Thunderbolt manual and the monitoring software (tboltmon that is referred to in the Time-Nuts message list).

if lives here: http://www.trimble.com/support_trl.asp? ... ction-2357

Have not fired it up yet but thought I would post in case others wanted it at some time in the future.

[VK5PJ]

Okay have turned the Thubderbolt on and the freq. counter is getting a work out.

After some looking I found the URL for the Thunderbolt manual and the monitoring software (tboltmon that is referred to in the Time-Nuts message list).

if lives here: http://www.trimble.com/support_trl.asp? ... ction-2357

Have not fired it up yet but thought I would post in case others wanted it at some time in the future.

as they say a picture is worth 1K of words. so I have attached a piccy of the monitor program, it has only been on for a few minutes, so the internal survey had not completed. Now all I have to do is wait for it all to settle then try and bring the counters reference into line, it shows as being 5.1 Hz low at present. (I want it to be independant for a while)
This pretty well proves that anyone can add a GPS based freq stabdard to their shack for a reasonable cost.

[VK4VU]

Gents,

The typical low cost GPS antennas have little or no filtering between the antenna and the first LNA stage.

This can be an issue where the GPS antenna is located in proximity to any 23cm transmit antennas.

This has been discussed in the following article by Chip N6CA

http://www.ham-radio.com/n6ca/microwave ... _ants.html

In my own case, I've not experience any issues with 120w Tx power on 23cm - but I do have > 10m vertical separation between the GPS antenna and the rest of the antennas.

73

Rod Preston VK4KZR

[VK4QB]

Hi All,
Can anybody tell me why I shouldn't use the my TV Derived frequency standard which I think is 1p in10^11th at 10 mhz for a frequency scource.Its locked to the ABC sync pulses which have a Rubidium standard. GPSs cost money.and I have this 10 mhz standard already. Sure, its not quite as good, but hey, Its free.
Brian 4QB

[VK2OMD]

Hi All,
Can anybody tell me why I shouldn't use the my TV Derived frequency standard which I think is 1p in10^11th at 10 mhz (sic) for a frequency scource (sic).Its locked to the ABC sync pulses which have a Rubidium standard. GPSs cost money.and I have this 10 mhz(sic) standard already. Sure, its not quite as good, but hey, Its free.
Brian 4QB

Brian,

Two thoughts come to mind.

1. Is your reference dependent on analogue TV transmission which will close soon?
2. It is one thing to specify the mean accuracy of a reference, or to assume that it is the same as its reference, but phase jitter is a really important parameter that may limit some applications.

Whilst it works, and for applications that it suits, why wouldn't you continue to use it?

Ref-locking a transceiver with a high phase noise reference degrades receiver performance. There is little point in being on-frequency if the system sensitivity is severely degraded.

There are some interesting things happening in the development arena. An interesting architecture is a CPLD based synthesiser with digital MASH filter for a low phase 10MHz GPS reference. Hand in hand, similar developments in fractional-N synthesis will deliver lower phase noise / higher resolution synthesisers for microwave LOs.

So, by the time you might want to upgrade for a specific application, there may be better devices available.

Owen

[VK4QB]

Owen,
You have given me food for thought. Thanks. I'll have to look into these things much, much further. But then again, if you ask ,then hey, there is a an answer ! Not so good, but then, not too bad either, and we can see the problems of using it, in a clearer light. If we don't ask we cannot see the problems at all.
73
Brian 4QB .One of the older breed