[time-nuts] Re: Power and heat re: Heathkit WWV clock / where are the good oscillators?

[Bob kb8tq]

Hi

> On Aug 8, 2022, at 12:17 AM, Hal Murray via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 
>> I've seen numerous reports of the flawed power supply and regulator, and the
>> intense heat it generates in the chassis, and I'm stumped. Why does it need
>> so much power that it's getting hot?
> 
> Wikipedia doesn't have a page on the Heathkit GC-1000, but it is mentioned on 
> their Radio clock page and says 1983.
>  https://en.wikipedia.org/wiki/Radio_clock
> and that has a link to:
>  https://www.pestingers.net/pages-images/heathkit/radio-equipment/gc1000/gc100
> 0.htm
> which has a set of pictures, one shows "13w max"
> 
> 10 watts in a plastic box.  I'm not surprised it gets hot.
> 
> Why does it need so much power?  You are comparing 40 year old technology with 
> with your expectations calibrated on modern technology.
> 
> A couple of differences:
>  CMOS technology
>  LCD vs LED
>  WWVB vs WWV
>  Switching power supplies
> 
> It would be fun to see a plot of the power needed to run a watch over the 
> years.

The low power CMOS process turns out to be pretty old. Indeed it is not a 
common thing to see used today or even back a while. They certainly have
improved it over the years, but it was already good when watches first came
out. 32 KHz is low enough that leakage gets you as you shrink things. It goes 
as fast / almost as fast / faster than the improvement in speed / power helps you. 

Another thing that “helps” is that very little of the IC is running at the “fast”
32 KHz frequency. The oscillator and first divider stages are pretty much 
all there is. Past that it just gets slower and slower as you go down the divider. 

Analog watch modules ( so a 32 KHz crystal driving a stepper that moved
hands) could run for a year on the coin cell battery in the watch back in the 
1970’s. The LCD versions …. not so much. 

Making the comparison a based on “how long will it run” a bit problematic
is that we transitioned from mercury batteries to lithiums ( and then to better
lithiums ) along the way. 

Bob

> 
> Initial GPS receivers were $250K.  They came out about the same time.
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
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