[Test-Equipment] Austron Model 1250A instability

[J. Forster]

Subject:         FW: [Test-Equipment] Austron Model 1250A
   Date:         Thu, 9 Sep 2004 20:06:15 +0100
   From:         Hugh Klein <hugh.klein at npl.co.uk>

Hi John

I hope what follows is of some use to you and Alan.

-----Original Message-----
From: Peter Whibberley
To: Hugh Klein
Cc: John Davis
Sent: 09/09/04 16:36
Subject: RE: [Test-Equipment] Austron Model 1250A

Hugh,

As Alan Melia noted, we monitor the Droitwich 198 kHz carrier frequency
(actually the phase offset from our time scale) at NPL with a time
constant on the receiver's PLL of around 5 sec, so we would not see any
instability more rapid than this.

The Droitwich signal is phase modulated to provide a low bit-rate
message service for customers such as electricity supply companies, and
the observed instability might be due to this modulation. The phase
switching is +/- 22.5 deg at 25 bits/sec and is balanced (ie. equal
numbers of positive and negative phase changes over some period), but I
do not have any other information about the modulation scheme.

I hope this helps.

Regards,
Peter.
______________________________________________
Peter Whibberley
Time and Frequency Group
Division for Enabling Metrology
Building 1, Room 203
ext. 6746

> > -----Original Message-----
> > From: Hugh Klein
> > Sent: 31 August 2004 09:20
> > To: John Davis
> > Subject: FW: [Test-Equipment] Austron Model 1250A
> >
> >
> > Does the email below mean anything to you John? I see Alan
> > Melia has a website:
> > http://www.alan.melia.btinternet.co.uk/#interests which
> > includes a T&F section. John Forster is an electronics
> > engineer friend of mine in the US.
> >
> > Hugh
> >
> > -----Original Message-----
> > From: J. Forster [mailto:jfor at quik.com]
> > Sent: 28 August 2004 02:22
> > To: Alan Melia
> > Cc: Hugh Klein
> > Subject: Re: [Test-Equipment] Austron Model 1250A
> >
> >
> > I'll ask a friend at NPL.
> >
> > -J
> >
> > Alan Melia wrote:
> >
> > > Hi John just a postscript to my LF off air problems. After
> > getting more kit
> > > and not finding any problem in my receivers, I now believe
> > that there is a
> > > real instability in the BBC Droitwich carrier. I have
> > queried it with NPL
> > > (our equivalent of your NIST) who pay the bills. They wont
> > find it in their
> > > usual measurements as they sample over a much longer time than the
> > > instability to get the higher accuracy. I only want parts
> > in 10^9 which is
> > > almost impossible quickly.
> > > regards
> > >
> > > Alan G3NYK