I've been running with a Trimble Thunderbolt GPSDO and the Elecraft TCXO for over a year now. I'm in a position to keep the Trimble powered up continuously, but I can certainly understand the angst of those who can't. It's a trade-off. I also keep an old laptop running, and have Lady Heather running on it to keep an eye on things. Do I really *need* that level of precision? Probably not, for my current operational needs (ordinary/casual HF operations, no VHF/UHF transverters, etc.). Bear in mind that the GPS receiver decodes the signals from the various satellites that can be seen at any given time, and then generates an error signal to its internal TCXO running at 10MHz, which then spits out both a 10MHz signal, which we typically feed to the K3EXREF, and a 1 pulse per second square wave (which I'd love to feed to a wall clock). The issue is the 100 second warm-up time for the Trimble's TCXO, not the GPS receiver, although the latter usually needs, like any other GPS unit, a few moments to listen for, and synchronize, to satellite signals.
There are a couple of system design issues inherent in this, however. First, the Trimble requires a triple-voltage power supply: +5V, +12V, and -12V. I'm using a cheap commodity power supply that is in itself powered from AC mains (117V/60Hz). So, if I lose AC mains, I lose the Trimble, and have to hope that the K3 and its TCXO will stay accurate enough while I'm operating it off of a battery. For those purposes, a few Hz isn't going to get me kicked out of an amateur net, but if I were a MARS member (which I'm not), it might be dicey - I'd have to do an analysis. The third issue, which has not been touched on AFAICT, is that the Trimble (and probably its competition) really likes to have an external antenna. In my case, I was lucky to find the actual Trimble antenna (which includes a preamp), and it's served me well at both of my QTHs (So. Fla. and western NC), which is a square puck about 2 inches/5 cm on a side with a magnetic base and 25 feet of RG-174/U coax. It works, and it was cheap on E-Bay, so I'm happy so far. So, a potential add-on product for the K3 could involve one of the newer single-board GPSDOs (e.g., Sematron GPS-1000 or one of its competitors), feeding the K3EXREF board internally and using the K3EXREF's input port on the back panel of the K3 for its antenna port. However, I haven't even priced one of these units, never mind purchased and evaluated it, much less actually attempted to install it in my rig. So, far, it's just an idea or springboard for further discussion. Brian makes an excellent point about the overall temperature requirements, as well as the behavior of the K3 running with its TCXO synchronized to a potentially unsuitable reference signal. These can be tricky design issues, and I'm sure Wayne and Eric have enough other things on their list to tackle at this point, without a digression into this quagmire. Just my 20 millidollars' worth, 73 de N1HO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
