Like I guess quite a few others, I have been down the high stability reference route and currently have the following 10 MHz sources:
60 KHz (MSF and possibly WWV) locked plain crystal oscillator, it's based on the G4JNT MK2 from RadCom (http://www.g4jnt.com/freqlock.htm). It works well enough and is easy and cheap to build/align. The limitation is the short term stability which is perhaps academic when used to lock a HF transceiver and is around 1 part in 10^8 (same stability as the older UK Quartzlock 198 KHz units), also I am not sure how immune it would be in the presence of high levels of HF RF. Locks and stable within 5 minutes or so from switch on, low current consumption. Surplus rubidium... These appear from time to time, I was given one by a local surplus dealer who seemed to have more than there was a market for a few years ago. They are used in cellular and similar sites and are probably good for quite a few hours of service, however they have a finite life and appear on the surplus market when removed for upgrade or on routine service, so don't pay much for one. Current drain is quite high, typically needing 2 Amps at 24 Volts initially then dropping after warm up. Stable around 15 ~ 20 minutes from switch on. Needs additional power supply and cabinet/heatsink. GPS controlled crystal oven... Mine appeared on eBay as a part home built unit, there are a variety of these that pop up at times. Mine uses a Toyo high stability OCXO and is superbly stable and will site in perfect sync with the rubidium for days. Locked and stable around 15 ~ 30 minutes from switch on, needs well sited external antenna (not one sitting in the shack window). Current consumption around half that of a rubidium when fitted with an OCXO. The best option of all for a long term accurate reference. If you want an OCXO there are currently several "double ovens" listed on eBay.com for $45 including worldwide shipping from China. They need a GPS or MSF/WWV locked oscillator to set accurately on frequency, warm up time 15 ~ 30 minutes. High stability oscillators/sources can be compared for phase/frequency with a dual beam oscilloscope, listening for a beat note between them is not sufficient at this level of accuracy. I don't plan to fit a K3EXREF, it seems like a nice idea but my K3 was only 2 Hz off frequency at 50 MHz a few days ago and it hasn't been adjusted for several months. My K3 has the KTCXO3-1 fitted and dates from 2007, so the TCXO is fairly well aged by now. 73 Dave, G4AON ----------------------- /I am considering a K3EXREF just for fun, no other reason. Looking for suggestions for a reasonably priced 10 MHz external signal source. Can anyone offer some suggestions? GPSDO? OCXO? Rubidium Standard? <SNIP> 73 de N1LQ-Dave/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
