msuhar at woh.rr.com
Fri Dec 29 14:32:11 EST 2006
I also sent the Spectrum Lab data to a spreadsheet. Once I got the carrier
at the frequency I wanted I did not touch the receiver. I made two mistakes
this time: 1. I did not record a wav file, 2. my FFT settings were such that
it made tuning difficult. The settings were fine once I found the carrier
but getting there was another matter. Because of this I was unable to tune
in the 40-meter signal. I found it just as the test ended but it was too
late to get any data.
I used an HP 3586C Frequency Selective Voltmeter with the tracking generator
looped back to the RF input via a step attenuator. The audio output went to
the PC. An ICOM IC-745 was tuned to the 160M signal to hear the test
announcements throughout the test period. The antenna on the HP was a SWL
slopper antenna that favors the lower frequencies. The ICOM was on a
160M: 1 854 317.77 [ARRL: 1 854 317.5 Hz]
80M: 3 587 117.82 [ARRL: 3 587 117.5 Hz]
I did not attempt to receive the west coast signal.
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of James Maynard
Sent: Friday, December 29, 2006 2:14 PM
To: k5cm at azalea.net
Cc: tim-nuts mailing list
Subject: Re: [time-nuts] FMT
Yes. I regret now that I rounded off the WA6ZTY frequency to the nearest
0.1 Hz. I might have been exactly in agreement if only I had rounded to
the nearest 10 millihertz.
I used a Ten-Ted RX340 receiver, which has the advantage that it accepts
an external 10 MHz frequency reference at its rear panel and phase-locks
all its oscillators to the 10 MHz reference. That made the measurement
comparatively easy. I would set the receiver for CW reception with its
BFO offset 800 Hz from the center of the passband, and feed the output
to SpectrumLab, running on my laptop with an external USB sound card. I
calibrated the sound card against WWV audio before the test.
I captured the Spectrum lab measurements to a text file, which I
imported into Microsoft Excel to compute the mean and standard deviation
of the peak frequency within a passband centered on 800 Hz. This worked
well for the W1AW measurements: once having tuned the receiver, I left
its dial alone for the duration of the test. As I recall, the one-sigma
jitter on the received W1AW frequency was 1 or 2 Hz -- so I certainly
did NOT consider my measurement more accurate than about 0.1 Hz.
Unfortunately, when it came to the WA6ZTY part of the test, I
kepttweaking the receiver frequency by a Hz or so (it tunes in one-hertz
steps) and that made the spreadsheet file captured from SpectrumLab less
useful. I didn't fell confident that I had made a good estimate of the
standard deviation of the measured frequency. because of my mistake of
tweaking the receiver frequency. So I rounded that measurement, too, to
the nearest 100 millihertz.
If I had only NOT disturbed the receiver tuning during the WA6ZTY
frequency measurement, I could have made a better estimate of the
one-sigma frequency jitter. Then I would have had a better estimate of
the accuracy of the measurement, and might have rounded it to the
nearest 10 millihertz rather than to the nearest 100 millihertz.
Salem, Oregon, USA
Connie Marshall wrote:
> Hi James,
> Looks like your W1AW 40m reading is inline with the rest of the readings.
> still think Joe (W1AW station manager) may have just made a typo mistake
> when he copied the readings to the email he sent me. My W1AW 40m signal
> good, about 55 db out of the noise on Spectran. My WA6ZTY signal was fair
> good. My reading for WA6ZTY would be the same as yours if I rounded to the
> nearest tenth.
> Would be nice to find someone capable of doing 2 or 3 runs per year. I'm
> wondering if WA6ZTY would be interested in doing some unofficial FMT runs
> several times a year. Sure would help get the math errors out, if we all
> more than one shot per year. I would be glad to do it but I wouldn't be
> anymore accurate than W1AW on TX as I currently have no way of locking my
> signal to a stable standard. But then again, maybe high accuracy is not as
> important as just the experience of getting it all together to make a
> measurement under the time pressure of 3 minutes. Were you active in the
> days when W1AW made 3 or 4 FMT's per year and reading to the nearest Hz
> considered good hi hi.
> Hope your having a good Holiday Season
> PS: by the way my Daughter's call is N5KK
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of James Maynard
> Sent: Friday, December 29, 2006 4:22 AM
> To: tim-nuts mailing list
> Subject: Re: [time-nuts] FMT
> My numbers were:
> W1AW (40 m band): 7038806.3 Hz
> (1.4 Hz higher than the official reading)
> WA6ZTY: 7028351.5 Hz
> (0.03 Hz higher than the official reading)
> I only submitted readings to the nearest 100 mHz (that is, 0.1 Hz),
> as I didn't think my measurements supported more digits of precision
> than that.
> I could not copy W1AW by ear, although I did pick out the call sign
> once during the test. I could not copy the announcements of when they
> were measuring the 160 m, or the 80 m, or the 40 m signal. I only saw a
> faint waterfall trace, and only on 40 m.
> James Maynard, K7KK
> Salem, Oregon, USA
> time-nuts mailing list
> time-nuts at febo.com
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