How low (V) can the K3 go?

[Chris Kimball]

I'm running a test on my K3 with Olivia 8/500 data mode at 40 W output. The duty cycle is 1/3 transmit (4 min) and 2/3 receive.  A "LOW BAT" warning and beep occur occasionally during transmit, however, the ALC remains at about 4 bars solid, one flickering.  The voltage during receive is more than 11 V, but during transmit it drops into the 9.x range sporadically.

The test is into a dummy load and I have no way to judge the signal quality.

When, at this power level, should I stop the test?  What's the best indication that the voltage is too low for a clean and usable signal?

Chris
NQ8Z

[Matt Zilmer-2]

The K3 / K3S is rated to meet its specs with a power source between 11
and 15V.  The problem with operating at low voltages is that the TX IMD
increases.  Distortion of any type is one of the enemies of data modes.  
Well, really, ALL modes.

I wouldn't operate the K3 / K3S much below 11.5V, personally.  A
solution for battery operation when the source voltage is too low is a
battery booster such as the N8XJK :
http://stores.tgelectronics.org/the-new-n8xjk-boost-regulator/. These
devices have a setting to go into an alarm state if the source voltage
is too low (I set mine to 10.5V), and you can set the output for up to
15VDC even with a source voltage as low as 9 VDC.  This will all work
with a power supply as well.  You may want to beef up your supply
cabling if you're seeing such a large voltage drop from source to K3.

If you're using a battery, read the specs to determine the lowest safe
operating voltage.  Running a battery discharging below this minimum
voltage will shorten its life (called overdischarge).

73!

matt W6NIA


On 9/16/2016 8:54 AM, Chris Kimball wrote:

> I'm running a test on my K3 with Olivia 8/500 data mode at 40 W output. The
> duty cycle is 1/3 transmit (4 min) and 2/3 receive.  A "LOW BAT" warning and
> beep occur occasionally during transmit, however, the ALC remains at about 4
> bars solid, one flickering.  The voltage during receive is more than 11 V,
> but during transmit it drops into the 9.x range sporadically.
>
> The test is into a dummy load and I have no way to judge the signal quality.
>
> When, at this power level, should I stop the test?  What's the best
> indication that the voltage is too low for a clean and usable signal?
>
> Chris
> NQ8Z
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/How-low-V-can-the-K3-go-tp7622535.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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--
Matt Zilmer, W6NIA
www.elecraft.com
Office: 831-763-4211 x125
Mobile: [phone]
[Shiraz]

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[wayne burdick]

The K3 will actually continue to operate well below 11 V, which is rare for any desktop transceiver. It will automatically reduce maximum allowed transmit power output, to some degree, based on the supply voltage. This allows use from a depleted 12-V car battery, for example. Our objective is to keep you on the air even in less-than-ideal conditions.

But as you noted, higher supply voltages result in improved IMD performance. Low voltages should only be used when there's no other choice.

73,
Wayne
N6KR


On Sep 16, 2016, at 9:12 AM, Matt Zilmer <[hidden email]> wrote:

> The K3 / K3S is rated to meet its specs with a power source between 11 and 15V.  The problem with operating at low voltages is that the TX IMD increases.  Distortion of any type is one of the enemies of data modes.  Well, really, ALL modes.
>
> I wouldn't operate the K3 / K3S much below 11.5V, personally.  A solution for battery operation when the source voltage is too low is a battery booster such as the N8XJK : http://stores.tgelectronics.org/the-new-n8xjk-boost-regulator/. These devices have a setting to go into an alarm state if the source voltage is too low (I set mine to 10.5V), and you can set the output for up to 15VDC even with a source voltage as low as 9 VDC.  This will all work with a power supply as well.  You may want to beef up your supply cabling if you're seeing such a large voltage drop from source to K3.
>
> If you're using a battery, read the specs to determine the lowest safe operating voltage.  Running a battery discharging below this minimum voltage will shorten its life (called overdischarge).
>
> 73!
>
> matt W6NIA
>
>
> On 9/16/2016 8:54 AM, Chris Kimball wrote:
>> I'm running a test on my K3 with Olivia 8/500 data mode at 40 W output. The
>> duty cycle is 1/3 transmit (4 min) and 2/3 receive.  A "LOW BAT" warning and
>> beep occur occasionally during transmit, however, the ALC remains at about 4
>> bars solid, one flickering.  The voltage during receive is more than 11 V,
>> but during transmit it drops into the 9.x range sporadically.
>>
>> The test is into a dummy load and I have no way to judge the signal quality.
>>
>> When, at this power level, should I stop the test?  What's the best
>> indication that the voltage is too low for a clean and usable signal?
>>
>> Chris
>> NQ8Z
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/How-low-V-can-the-K3-go-tp7622535.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
> --
> Matt Zilmer, W6NIA
> www.elecraft.com
> Office: 831-763-4211 x125
> Mobile: [phone]
> [Shiraz]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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[Guy Olinger K2AV]

The manufacturer has clearly, often, repeatedly stated, and keeps posted
their specification that the K3/K3S is designed for 11 to 15 volts.

Optimum THD is at the high end of that range. I have my supplies set at
14.4 VDC for this reason. This is also the bulk charge voltage for my "12"
volt batteries which proves handy at times.

Your operation at nine point something is simply out of bounds. Batteries
with 9 volts in their routine sustainable discharge curve are inappropriate
for the K3/K3S.

Operating any data mode away from the point of best linearity is poor
practice other than for continuation of communication in emergencies. For
normal operation, especially data, if you aren't operating at 14.4 then fix
it so you are. Stay there.

Discharging lead-based batteries below 11 volts will shorten life. Each
time you let batteries drop below 11 volts the length of time decreases
that you can operate below 11 volts following a recharge.

If you are into emergency preparedness, you save the south of 11 volt
operation for actual emergencies where you don't have a choice. Remember
that when you go south of 11 you are using up the battery's useful life.
The manufacturer is telling you that the K3/K3S is not designed for south
of 11.  South of 11 is a foul ball.

Personally I manage the huge T105's in my RV to stay above 11.5 VDC in
camps without power hookup. They are expensive, very heavy, and a real pain
in the *ss to change out.

73, Guy K2AV

On Friday, September 16, 2016, Chris Kimball <[hidden email]> wrote:

>
> I'm running a test on my K3 with Olivia 8/500 data mode at 40 W output. The
> duty cycle is 1/3 transmit (4 min) and 2/3 receive.  A "LOW BAT" warning
> and
> beep occur occasionally during transmit, however, the ALC remains at about
> 4
> bars solid, one flickering.  The voltage during receive is more than 11 V,
> but during transmit it drops into the 9.x range sporadically.
>
> The test is into a dummy load and I have no way to judge the signal
> quality.
>
> When, at this power level, should I stop the test?  What's the best
> indication that the voltage is too low for a clean and usable signal?
>
> Chris
> NQ8Z
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.
> nabble.com/How-low-V-can-the-K3-go-tp7622535.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <javascript:;>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email] <javascript:;>
>

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[Chris Kimball]

Just to complete the picture, I was away from the test for a bit and came back to find the K3 turned off.  It came right back when a reasonable voltage was applied.  Very likely, the voltage got too low at one point in the transmission and sent the internal computer down.  When it's down, you're done!