[time-nuts] How accurate are cheap radio controlled clocks?

Ron Smith ronald.p.smith at btinternet.com
Mon Jun 27 08:46:33 UTC 2011


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" <david.kirkby at onetel.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
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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