[Elecraft] K3EXREF Query

[Geoffrey Downs]

Ed, you restate the problem and a simple solution but quite apart from the 
cost (which is trivial or not depending on your circumstances) we should 
all, in my view, be trying not to use energy unnecessarily in the interests 
of our grandchildren. There is also a potential fire risk with a unit that 
is running permanently.

A preferable solution would be some means for the K3 to ignore the external 
reference until it has stabilised after switch-on. This issue has so far 
deterred me from buying a K3EXREF but it's not a big issue because the K3 is 
so stable and accurate and Ref Cal needs to be checked only occasionally. In 
fact I presume that once the external standard has set the K3  through the 
EXREF the K3 stays put when the reference is switched off so you could leave 
your reference off most of the time and only put it on when you are not 
planning to use the K3 for half an hour or so and want to check the 
calibration.

73

Geoff
G3UCK

-----Original Message----- 
From: Edward R Cole
Sent: Tuesday, October 14, 2014 10:47 PM
To: Elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3EXREF Query

David,

10w is 7.3 kwH/month.  I would doubt that is a large expense, even in
GB.  Locally, its about 8 cents/kwH but in the bush it might be as
high as a couple dollars since diesel fuel for the generators costs
are huge (local diesel is $4.10).  I know it would require conversion
to liters and all that to come up with equivalent costs, but most
households run hundreds of kwh/mo.  Leave your TV plugged in but
turned off and it still consumes about 50w.  I have plug strip to
remove ac from all my home TV systems when not in use.  I leave power
to the satellite receiver as it keeps the LNB powered and stable
(Otherwise it takes 5-10 minutes to acquire signal and download data
at startup).

Simple solution is to leave the reference oscillator running
continually.  The K3 TCXO-3 will still drift on power up but this is
compensated by EXREF every 4-seconds so frequency stability is held
to better than 0.1 ppm.  I measured +/- 2 Hz at 28-MHz on my K3.  But
if you watch the REF*CAL frequency you will note it incrementing from
49.380.000 to something like 49.380.080 in several minutes and then
settle down near that value (indicating start-up drift has stopped).

By not running your reference full time you will have to wait 15 to
30 minutes for it to fully warm up.  I also have a rubidium but run
it only for precise frequency calibration of the OCXO couple times
per year.  My mw counter internal TCXO is always in agreement with
the Rb so I do not bother for routine frequency checks.  The rb is
only +/- 5 E-11 so not as good as GPS but good enough for my use.

73, Ed - KL7UW
-------------