[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.
Regards
Paul
WB8TSL

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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