Time-Nuts Thunderbolt GPSDO Group Buy

IMPORTANT NOTE: THIS PAGE IS WORK IN PROGRESS

The Trimble Thunderbolt is one of the more popular GPSDO with amateur timekeepers, and rightfully so. It provides excellent performance at moderate cost, and one of the more interesting features of the design is the capability to modify many of the operational parameters of the device and the availability of comprehensive control and monitor software that allows to tweak these parameters, see their effect and possibly optimize the Thunderbolt for a particular set of requirements or operating conditions. For example, John Miles has replaced the internal OCXO with a higher performance oscillator and optimized the Thunderbolt for it. The Thunderbolt is not only a useful tool, it is also a great learning tool.

Those who were on the Time-Nuts mailing list around the 2008-2009 time frame probably remember the Trimble Thunderbolt GPSDO group buy, organized by Tom Van Baak and sold through TAPR.

Tom took the pain to acquire a large number of devices from a reputable US source, check and evaluate them, find a suitable matching power supply, procure the bits and pieces to hook it all up together and made a deal with TAPR for the distribution of the devices to end users at a price well below those on the usual sources and with Tom's reputation behind it.

This offer appears to have at the time saturated the market and Tom was left with a significant number of units. Now a few years later, Tom suggested making the remaining units available through this web site.

You can find more information on what is offered through Tom's Group-Buy Thunderbolt page and the FAQ page.

Please note that these devices are part of the same US-made group as the original devices and are not "second grade" in any way, shape or form. However, the quantity is quite limited and after that, it will be over.

The Group-Buy Thunderbolt GPSDOs have all been tested to make sure they acquire and track satellites and that the OCXO's control voltage is not near the rails. They are also checked on the spectrum analyzer to make sure they do not have significant spurs. If you get a defective unit in spite of these checks, return it for either replacement or refund. As the quantity is limited, I cannot guaranty that all returned units will be replaced and if not, you will be refunded. However Tom indicated that the return rate of the first batch was less than 1%.

Ordering Information

To order, use the Paypal button below if you live in the US or Canada (or send me a check in the mail if you are Paypal averse, address on demand). If you live abroad, send me an email and I will send you an invoice for your country. See below for international shipping considerations.

Thunderbolt GPSDO $275 + shipping

Note about international shipping

The US Postal Service (USPS) international rates have gone up considerably in recent years. I cannot quote a flat rate for overseas destinations, but you can see how much it is if you enter your specifics into the USPS Rate Calculator. Make sure you select your country and the cost of your purchase (in $US) and select Priority Mail International® Medium Flat Rate Box (see screen shot below)

In the example above ($275 value shipped to England), the cost came back at $66.50. Ouch!!!

The USPS does provide insurance for overseas shipments, but there are many caveats that are not disclosed up front and I know from experience that if problems arise, you may not get your money back. Therefore, I do not consider overseas shipment through the USPS as being effectively insured the way most reasonable people would understand it.

Finally, you may have to pay import duty on the equipment when you receive it. This is totally out of my control as I have no way of knowing in advance how much you will pay.

Lady Heather software

If you intend to get the most out of a Thunderbolt timing receiver, your best next stop is the Lady Heather software developped by Mark Sims with help from John Miles. You can download it from John's web page here.

Combined Purchase GPSDO and Monitor

If you want to buy a Thunderbolt GPSDO as well as a Thunderbolt Monitor Kit, you do not need to pay shipping twice. Use the Paypal button above to order the GPSDO and use the Paypal button below to order the kit without shipping.

Antenna

All you need to add is a GPS antenna. The choice is wide. Any antenna designed for GPS application will probably "work" (examples below), even though you may want to study the Thunderbolt User's Guide (see Links below) to make sure you get an antenna and install it in a way that allows the Thunderbolt to fulfill its potential. Studying the Time-Nuts archives and the links below will give you a lot more than a head start and is highly recommended.

Examples of GPS antennas available on eBay as of mid-March 2016 are below:

Inexpensive navigation antenna

Timing antenna

A navigation antenna will be enough to check the Thunderbolt and if you are in a good location, it may give good to excellent results. Typically, cheap antennas do not have a very well defined gain pattern and therefore are less protected against multipath, for example if the antenna is close to a metal roof or other obstruction. Their phase center is also not well defined, but for most casual applications, that makes little difference.

The HP/Symmetricom/Microsemi 58532A is a classic with excellent performance. It is typically available for about $40 on eBay. The base is intended to mount directly on a steel mast while you run the cable through the mast which will give you the cleanest look. Install the antenna in a location where it has unobstructed view of the south sky (in the northern hemisphere) and a couple of feet above the closest roof lines and you should be OK. Do not forget lightning protection if you care about your equipment or your house...

EDS-FL

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