I recently was trying to fix a horrible 6hz error on my Jupiter, and was
using WWV and spectrans to see what I could do.
After spending an hour or so tweaking settings, the WWV carrier turned
out as a *blob* of signal all around 10mhz. Absolutly useless to get a
center frequency, as the sides of this *blob* undulated with the
ionosphere - it never was pure gaussian.
What I figure happened was that I was effectivly getting an infinate
number of signals (rays) each transformed a certain amount in the
ionosphere, and ending up anywhere withing a *range* of 0-10hz. Each ray
got speed shifted a certain amount, and added a different spot on my blob.
Yes you can figure a median, but that would take a week or a month of
sampling to determine - even longer with more variance (like magnetic
storm activity)
So, I'm still 6 hz off :(
-Dan N7NMD
I
Carl Moreschi wrote:
I am having a hard time understanding where this propagation frequency error
could come from. It seems to me that if WWV was at 15 mhz and I was
receiving a 14.999990 frequency, this 10 hertz frequency error would be
building up some place in a time warp! I could understand an instantaneous
error over a few milliseconds but it should average out to be right on the
mark in a few seconds. If it doesn't, then either WWV or my station are
moving relative to one another and there is a doppler shift going on!
Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "Gary Hoffman" <ghoffman@spacetech.com>
To: <geraldj@isunet.net>; <tentec@contesting.com>
Sent: Monday, June 02, 2003 10:39 PM
Subject: Re: [TenTec] Some Observations on Orion Stability/Calibration
Jerry...
How do you know that propagation delays cause about a 1 ppm error ? I
have
not found that figure referenced elsewhere, and would like to know how to
measure or estimate it. Thanks !
Gary
----- Original Message -----
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
To: <tentec@contesting.com>
Sent: Monday, June 02, 2003 3:05 PM
Subject: Re: [TenTec] Some Observations on Orion Stability/Calibration
TC stands for Temperature Compensated, NOT Temperature Controlled. So
the oscillator controls should be responding to its environment.
But HF propagation causes short term variations in frequency of about 1
part per million, 20 HZ at 20 MHz WWV so the measurements may not be of
the TCXO but likely are of propagation changes. Frequency measurement
specialists expect it to take a month of averaging HF WWV signals to get
to within that 1 PPM. Hoping to do it in hours just isn't going to
happen.
Only propagation at VLF, like 20 and 60 KHz can allow better frequency
distribution than a PPM, and then its not right if there's an aurora
about like there has been last week.
73, Jerry, K0CQ
--
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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