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.
>>>_______________________________________________
>>>TenTec mailing list
>>>TenTec@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/tentec
>>>
>>>
>>>
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>>
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