Re: [Elecraft] KX3 - Switching power source while operating

[Jim Brown]

To clarify --K3, K3S, KX3, and KX2 shut down sort of like a computer -- 
they write their complete setup to RAM when you turn them off, and that 
setup determines how they turn on. When you kill power by removing the 
power source, that write doesn't occur, so the radio turns on (reboots) 
with the last saved settings, which may be quite different from where 
you had set them for the setup when you lost power. I've learned this 
the hard way. :)


So -- like others have advised, the best solution is to keep a charged 
battery set in the radio, so that when you lose external power, the 
radio doesn't have an un-planned event.


73, Jim K9YC

On 6/28/2017 2:28 PM, Terje Elde wrote:

I’m wondering if anything is known about how much of an intermittent loss of 
power a KX3 will more or less not notice, during full use (transmit at 15W), 
and during receive?



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Re: [Elecraft] KX3 - Switching power source while operating

[Mark Petiford via Elecraft]

Grant,

RE:  "Seems to me the most straightforward approach would be to put a set of 
batteries in the KX3.  Then you can drop and restart external power without 
worrying about the time delay."

That was exactly my first thought as well.  It certainly works fine on receive 
and it solves the "improper shutdown forgetfulness" problem, but i'm not sure I 
want to pull out the power cord during transmit to see what happens.  I just 
don't know enough about the power control feedback loop to know how it would 
react to a sudden change in voltage.


Anyone want to put their KX3 into transmit and then pull out the power cable to 
see what happens?  Oh yea, then put it back in and see what happens.  Voltage 
transients like this are a very important part of aircraft electronics since 
bus switching and even EMP events induce such transients, but I would doubt if 
that was a design requirement for the KX3.  It is likely, however, that it has 
been tested inadvertently by now ;-)


Mark
KE6BB

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Re: [Elecraft] KX3 - Switching power source while operating

[GRANT YOUNGMAN]

Seems to me the most straightforward approach would be to put a set of 
batteries in the KX3.  Then you can drop and restart external power without 
worrying about the time delay.  The radio won’t care.  Only thing you might 
have to do is adjust output power if you were operating above the internal 
battery default … 


> On Jun 28, 2017, at 6:06 PM, Terje Elde  wrote:
> 
> 
>> On 28 Jun 2017, at 23:51, Ken G Kopp  wrote:
>> 
>> Wonder if a high capacity electrolytic capacitor would hide the effect of 
>> the "power bump"?
> 
> If the bump is short enough, and the caps are big enough, then I don't see 
> why not. From the perspective of the KX3, there shouldn't really be much 
> difference with the bump then. 
> 
> Mostly just wondering if anything is known about the KX3s tolerance alone.
> 
> I suppose the safer way would be to ignore that, and just consider the 
> duration directly against the caps, and keep the voltage sag above KX3s lower 
> tolerance. 
> 

Grant NQ5T
K3 #2091, KX3 #8342



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Re: [Elecraft] KX3 - Switching power source while operating

[Terje Elde]

> On 28 Jun 2017, at 23:51, Ken G Kopp  wrote:
> 
> Wonder if a high capacity electrolytic capacitor would hide the effect of the 
> "power bump"?

If the bump is short enough, and the caps are big enough, then I don't see why 
not. From the perspective of the KX3, there shouldn't really be much difference 
with the bump then. 

Mostly just wondering if anything is known about the KX3s tolerance alone.

I suppose the safer way would be to ignore that, and just consider the duration 
directly against the caps, and keep the voltage sag above KX3s lower tolerance. 

Thanks,
Terje
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Re: [Elecraft] KX3 - Switching power source while operating

[Don Wilhelm]

Terje,

A loss of power will not allow the KX3 to power down gracefully, so some 
information such as what frequency, mode, and other data may be lost.
To insure a seamless transfer between batteries, you may want to design 
your controls so that two battery packs are in parallel for a short time 
rather than creating a gap in the power source to the KX3.


73,
Don W3FPR

On 6/28/2017 5:28 PM, Terje Elde wrote:

Hi,

I’m wondering if anything is known about how much of an intermittent loss of 
power a KX3 will more or less not notice, during full use (transmit at 15W), 
and during receive?

Asking because I’m considering some power solutions, and wondering if it could 
be useful to switch between multiple battery packs in an automated way.  For 
that, it’d be useful to have some design targets.  I’m assuming a loss of power 
for 1ns would be a non-issue, and I’m assuming 10 seconds would be a huge 
problem, but wondering if there are any definitive lines somewhere between 
those extremes?

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[Elecraft] KX3 - Switching power source while operating

[Terje Elde]

Hi,

I’m wondering if anything is known about how much of an intermittent loss of 
power a KX3 will more or less not notice, during full use (transmit at 15W), 
and during receive?

Asking because I’m considering some power solutions, and wondering if it could 
be useful to switch between multiple battery packs in an automated way.  For 
that, it’d be useful to have some design targets.  I’m assuming a loss of power 
for 1ns would be a non-issue, and I’m assuming 10 seconds would be a huge 
problem, but wondering if there are any definitive lines somewhere between 
those extremes?

Terje

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