Hi Jeff,
For about $150 you can get a used Trimble Thunderbolt GPSDO that will give you a precision 10 MHz reference signal to put into your Flex Radio. Tune in WWV and watch the Phase display. The rotation is from Doppler. After parking the rig at a convenient frequency a couple of hundred Hertz below the signal of interest, I use PowerSDR to record a receive post-processing USB wave file while the test is going on. I run the free Spectrum Lab software while playing back the wave file and watch the signal on the Spectrum Lab waterfall. You can see it wander in frequency when the propagation changes. Add that audio frequency to the frequency displayed in PowerSDR. I make my best guess for the middle of the Doppler swings and send it in. My PC is nothing special, just an AMD Athlon 64 2 GHz and Windows XP. Oh, and download the free Lady Heather software for monitoring your Thunderbolt. An awesome program. The ARRL FMT is on November 10th. Join the fun. It's not about reading to the milli-Hertz; it's about developing your skills in frequency measurement. Mike - AA8K On 10/09/2010 06:14 PM, Jeff Singer wrote:
Thanks for the alert on the K5CM Frequency Measuring Test a few nights ago. That test uses two stations to send a CW carrier on 160, 80 (twice) and 40 meters. A FMT is something totally new to me. My only preparation was to calibrate the radio carefully against WWV using its built-in scope. My receiver was in the DSB mode. I used the scope to guess-timate the frequency to an additional decimal point. Few entrants use a radio alone. Many have costly GPS based frequency calibration sources or the like and complex schemes to interpret the frequency. Experience counts. So does speed, since you only have three minutes to come to a conclusion. In other words, my entry wouldn't threaten the experts who come within one or two MILLI-hertz. But my stock Flex did very well. Three of my four readings were within 1/2 Hz. On 40 meters I was off by .96 Hz. QRN on 40 made the weak signal difficult to read on the scope. Still, accuracy was better than .25 PPM on each reading, well within Flex specs. Anyone else participate? Jeff K0OD
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