[time-nuts] Thunderbolt SV and AMU Signal levels

Ulrich Bangert df6jb at ulrich-bangert.de
Wed Jul 23 02:48:52 EDT 2008


Gents,

just in order to prevent anybody into believing that

> Variation of +/- one count in the last digit is normal for 
> any counter.  It 
> is caused by a slight shift between the counter gate and the 
> input signal. 
> The longer the time between digit changes, the more stable 
> the phase between 
> the unknown and the counter gate.

were some kind of universal truth: This resembles the counter technology
of some 30-40 years ago and you will not find any counter model of any
serious manufacturer that uses "gate times" (if this term should be
allowed at all today) which are uncorrelated to the input signal.

I am well aware of the fact that the existence of easy programmable
microcontrollers and cheap high frequency dividers have encouraged
zillions of amateur developers to publish mcu based "frequency counters"
that work the way as described above. Nevertheless this is by far not of
the technology of today.

Best regards
Ulrich Bangert

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von John Franke
> Gesendet: Mittwoch, 23. Juli 2008 02:28
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Thunderbolt SV and AMU Signal levels
> 
> 
> Variation of +/- one count in the last digit is normal for 
> any counter.  It 
> is caused by a slight shift between the counter gate and the 
> input signal. 
> The longer the time between digit changes, the more stable 
> the phase between 
> the unknown and the counter gate.
> 
> John  WA4WDL
> 
> ----- Original Message ----- 
> From: "David Ackrill" <dave.g0dja at tiscali.co.uk>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> Sent: Tuesday, July 22, 2008 7:14 PM
> Subject: [time-nuts] Thunderbolt SV and AMU Signal levels
> 
> 
> > Sorry to be a bore, but like any kid with a new toy I'm 
> facinated by 
> > the changing values on the display...
> >
> > What do the values under SV and AMU mean?
> >
> > Maybe I should recognise them from other GPS satellite 
> days, but they 
> > don't seem to be values that I remember.
> >
> > I'm sure it all means that they are to the north, south, 
> east or west 
> > of here and to do with signal strength to my location or 
> how good, or 
> > bad, the lock to the satellites is..  But, nothing that I can 
> > remember, to be honest...
> >
> > The 10MHz output seems, as far as my old Multifunction Counter is 
> > concerned, to be to 10.00000MHz within +/-0.00001 MHz.
> >
> > The display showing 10.00003 to 10.00004 MHz all evening.
> >
> > So, my guess is that my poor old counter is +/- 10Hz out, 
> but that may 
> > be due to the age and non-calibration of my frequency 
> counter over the 
> > years.
> >
> > Or... The Thunderbolt 10MHz output is moving up and down by 0.00001 
> > MHz within a 10MHz band.
> >
> > This is where I start to get to grips with the spectrum 
> analyser that 
> > a friend of mine lent to me.  I hope...
> >
> > Dave (G0DJA)
> >
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> > 
> 
> 
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