[time-nuts] (no subject)
colinbradley10 at yahoo.com
Wed Oct 18 14:34:37 EDT 2006
I will also try my hand at this November’s FMT. My first attempt at the FMT was back in the early 60’s from my home in Rochester, NY. I used a home brew counter that used a dozen 12AU7’s with NE2 readouts. It used a start gate that had to be manually started. At the end of the count I would add up the binary count displayed on the neon bulbs. The off air signal was beat against a 1kHz marker divided down from a 100kHz crystal oscillator. The whole setup barely worked. The biggest problem was the amount of noise on the audio signal from the receiver. The counter could not handle it.
In getting ready for this years FMT I rediscovered some of the lessons learned back in my youth. I loosely coupled a Fluke 6080AN into my Icom R70 receiver to beat against the unknown signal. I then tried to measure the resultant audio note with my HP 5370B. The same old problem. Too much noise. My next effort involved taking the audio output of the receiver to a scope that was triggered by the output of an HP 3325A function generator. This worked much better. By adjusting the frequency of the 3325A, I could stop the motion of the signal and read the offset from the function generator. Still not great, but it works. For this years attempt I will try John’s method. I loaded an old computer with a downloaded version of Linux. I have also downloaded a copy of Baudline audio analyzer. This looks to be a great program for this type of work. Once I have this combination working, I will calibrate Baudline with the 3325A. My time base collection consists of a pair of 5061A’s,
several rubidium oscillators and three HP Z3801’s. I keep an eye on their performance with a NIST frequency measurement system that uses GPS as a reference.
My home is located in Boulder, Colorado. Recent measurements of W1AW showed that their signals are weak at 1700 miles. The Bay area on the west coast is about 1100 miles. Boulder is not ideally situated for either location. Good for WWV or WWVB however! The FMT should be fun.
Colin Bradley WA2YUN
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