[Elecraft] K3EXREF Query

Wed Oct 15 15:12:58 EDT 2014

Folks let me set a few things straight. I have designed a few high stability time bases and I have done the lab work so I am confident of my facts.

First, you never want to use AC or bimetal thermostats for precision oven heaters because they are inherently noisy and ultimately unstable. Bimetal is a bang-bang controller and starts having short time stability troubles at one part in 10 minus 7. This type of controller may have a long term stability of 10 to the minus 9 (which will be advertised) but you must have short stability. After all the timebase is for a radio, not a clock so any comparison to clocks (or coffee makers) is bogus. 

Second, there is no such thing as a perfect insulator. Even a vacuum  thermal bottle type oven will use energy. When the oven is warming from turn-on lots of energy is needed; not so much for maintaining a constant temperature. This is a classic trade-off. Do you have a big heater for fast turn-on or a small heater for precision? 

Third, on a level playing field an 'always on oven' will always consume more energy than a 'on demand' system. The claim 'always on' is more efficient is bogus. Unlike a race car, there is no startup penalty caused by inefficient  acceleration. However, this may not be true of the oven power supply.

Fourth, a dedicated power supply for the heater is usually the bigger waster of energy. The dedicated power supply is another trade-off. Use a linear and waste a lot of energy. Use a switcher and generate noise. 

Fifth, California has a law that says standby devices (like that wall wort plugged into the wall but not otherwise connected) my not waste more than 3 watts of energy. This applies to TVs that are plugged in but turned on. I don't think there is any enforcement for this law so I'm sure some violate it. Nevertheless manufactures don't want to be branded as energy hogs so most big manufactures comply. Also they do not want to have California only designs so the law is applied to all designs. All states and all counties benefit. Look at cell phone chargers where the light switchers are used instead of the heavy wall wort linear supplies. You thought it was to save weight?

73
Fred, AE6QL

-----Original Message-----
>From: Edward R Cole <kl7uw at acsalaska.net>
>Sent: Oct 15, 2014 9:29 AM
>To: Elecraft at mailman.qth.net
>Subject: Re: [Elecraft] K3EXREF Query
>
>Lynn,
>
>That was a guess and probably way too high.  I have 3-year old 
>46-inch LED flat-screen.  But also a home theater receiver rated to 
>125w audio and two DVD drives, a VCR and satellite receiver.  So all 
>the remote control power supplies do add up - to what? I do not know 
>- haven't measured the total load.
>
>But since the TV is on from 5pm-10pm and off the rest of the day it 
>seems there would be some savings by disconnecting the ac power.  We 
>have a six outlet strip which makes that simple.  It does reduce fire hazard.
>
>On the other hand I keep my Astron station 12v supply on full time 
>which supplies the OCXO, so I do not have any delay waiting for it to 
>stabilize.  I have my ham gear on more frequently than the TV.
>
>We make a pot of coffee (fresh ground) in the morning and turn-off 
>the maker after it finishes.  Coffee pot draws quite big load keeping 
>water and coffee pot hot.  And that only ruins the coffee.  We just 
>reheat a cup in the microwave when we want hot coffee.  Do we save 
>any power this way??  But the coffee tastes better :-)
>
>73, Ed
>
>-----------
>From: "Lynn W. Taylor, WB6UUT" <KX3 at ColdRocksHotBrooms.com>
>To: elecraft at mailman.qth.net
>Subject: Re: [Elecraft] K3EXREF Query
>Message-ID: <543D9E2C.9000306 at ColdRocksHotBrooms.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>On 10/14/2014 2:47 PM, Edward R Cole wrote:
> > Leave your TV plugged in but turned off and it still consumes about 50w.
>You need to buy a new TV.  The new ones are under a half-watt when
>plugged in but turned off.
>
>
>73, Ed - KL7UW
>http://www.kl7uw.com
>     "Kits made by KL7UW"
>Dubus Mag business:
>     dubususa at gmail.com
>
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