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

paul swed paulswedb at gmail.com
Mon Jun 27 02:37:24 UTC 2011

The clocks are amazingly inexpensive these days typically sub $10. Pretty
amazing and run on 1 aa battery. That said what I have seen is they tend to
stay right on time at least using my ear and a wwv rcvr. Granted if they do
not get sync for several days you do see them start to creep. But not much.

On Sun, Jun 26, 2011 at 2:15 PM, David <t_list_1_only at braw.co.uk> 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.
>>  David,
> I'd back what David Taylor says that I casually see my cheap Casio watch
> maintaining sync via the NPL Anthorn 60kHz signal within a second of BBC R4
> LW pips although it appears we are in the same neighbourhood. I back the
> idea that the clock is not syncing for one of the aforementioned reasons
> (local noise, clock orientation etc). Bear in mind R4 LW at Droitwitch is
> not a single national service, there are two other transmitters that tend to
> be forgotten, the R4 198kHz signal Dave & I pick up may be the one
> transmitted from Westerglen rather than the NPL monitored signal from
> Droitwich (see 1). I've never seen anything authoritative regarding how the
> Scottish transmitters are controlled for carrier stability or modulation
> delay (audio or time code) nor anything about mutual interference zones. The
> NPL reports relate only to Droitwich carrier accuracy (2).
> For the timenut, remember that R4 LW has a largely forgotten time code
> feature (3) which frees you from having to listen to the pips and John
> Humphrys, I wonder if anyone is monitoring this?
> (1) http://en.wikipedia.org/wiki/**Droitwich_transmitting_station<http://en.wikipedia.org/wiki/Droitwich_transmitting_station>
> (2) http://www.npl.co.uk/science-**technology/time-frequency/**
> time/products-and-services/**droitwich-bulletins<http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/droitwich-bulletins>
> (3) http://downloads.bbc.co.uk/rd/**pubs/reports/1984-19.pdf<http://downloads.bbc.co.uk/rd/pubs/reports/1984-19.pdf>
> Regards
> David
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