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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[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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[Terje Elde]

> On 28 Jun 2017, at 23:51, Ken G Kopp <[hidden email]> 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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[Grant Youngman-2]

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 <[hidden email]> wrote:
>
>
>> On 28 Jun 2017, at 23:51, Ken G Kopp <[hidden email]> 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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[Elecraft mailing list]

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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[Jim Brown-10]

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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