[Elecraft] K3S and power failure

[Bob McGraw K4TAX]

Well that condition of a power failure is never advised.   Likely the 
radio just won't save the last parameters.   And yes it is never advised 
to turn off the power supply before turning off the radio.    The radio 
saves the last used parameters when the power switch is depressed.   
This won't occur when the supply is switched off before the radio.

Yes, a UPS would be nice and will prevent such events but......be sure 
to get one that is sine wave {they usually generate less crud}  and one 
that does not generate RFI and birdies.    Usually "cheap ones" won't 
pass muster in this regard.  Good ones run with the output locked in 
phase with the power line and may actually supply power 100% of the 
time.   Others switch quickly to prevent power interruptions to the load.

The "quiet" method is to float a small battery, depending on how long 
you want to hold the system up, determines the Ah rating. If your supply 
is running a solid 13.8 to 13.9 then a lead acid battery of the 
garden/lawn mower type works just fine.  Connect the battery across the 
supply output.  A 20 amp or so fuse should be in the positive line 
between the battery and supply.    You should check to see when the 
supply is off that it does not draw current from the battery.  Most 
don't, yet some do.  This will discharge the battery when the supply is 
off.     I don't advise using diodes to isolate the battery from the 
supply and then feed the radio due to the voltage drop across the 
diodes.  Plus the diodes will need to be rated at the current of the 
supply and/or radio current demand, and those will likely require a heat 
sink.

73

Bob, K4TAX



On 7/17/2018 8:46 PM, Bob Novas wrote:
> My house occasionally has a power failure, typically lasting less than a
> minute. One just happened.  Do I have to worry about operating the K3S and
> having a power failure?  It would be like turning off the power supply
> without first turning off the K3S, and I understand that's not recommended.
> Do I need a UPS for the K3S?  What would be nice would be a small battery
> that powered the smarts independently of the mains supply.  Bob - W3DK
>
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