David,
I think Radio 4 on 198 kHz is straight through analogue - no digital
buffering with its inherent delays. Yesterday afternoon (1200 UTC I think),
I listened to the BBC pips from Droitwich at the same time as the pips from
RWM on 9,996 kHz, and I watched the second-hand of my Steiger
radio-controlled clock. All three were in exact synchronism - no error
between them, as closely as the ear and the eye could tell.
Are there different ways these radio-controlled clocks are synched to time
signals? I have never seen any perceivable error between my clocks and
analogue broadcast "pips" from MSF, RWM or WWV, so I don't think the synch
scheme is a corrective one. I will try keeping one of my clocks in a Faraday
screen for a while to see how far it drifts in terms of time.
I know of the other two 198 kHz transmitters at Westerglen and Burghead, but
don't know whether they have the same accuracy as Droitwich's frequency
standard. Do they carry the same phase modulation as Droitwich for
teleswitching?
Ron, G3SVW
Manchester
----- Original Message -----
From: "Dr. David Kirkby" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Sunday, June 26, 2011 3:22 PM
Subject: Re: [time-nuts] How accurate are cheap radio controlled clocks?
On 06/26/11 07:25 AM, David J Taylor wrote:
I've got one of the cheap radio-controlled clocks? I was listing to
radio 4 the other day and herd the time signal. The radio controlled
clock was about 3 seconds off. I was a bit surprised it was so far
off. I'm just wondering how accurate these things are.
David,
Be aware that if listening via digital radio (or worse, digital TV)
there is a delay in the transmission chain of up to several seconds
(DTV). I expect you know that already! Use the FM signal for best
results.
I was using 198.00 kHz longwave here in the UK. Unless there's some
digital processing going on before the signal is AM modulated, this can't
explain the problem.
--
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