[Elecraft] K3 13.8 VDC power

[david Moes]

I'm just curios  is there any real test data available showing what IMD 
may be present at  various supply voltages?   I have heard many comments 
on the reflector over the years saying to keep the voltage high  one 
member saying to keep it at 15V.    The specs say 13.8 V nominal during 
TX. (11 V min, 15 V max)       I would think that the transmit signal 
should be fairly clean within this range.

At home its on a regulated supply 13.8 so NP   but at the cottage where 
there is no utility power  its on a battery  with 6 and 10ga wiring  all 
using solar charge.  At night I will see voltages drop to about 12V 
after operating with lighting from the same battery for a while  usually 
about 1:00 am in a contest.  this is when I go off the air and to bed, 
as this is typically about when the battery reaches a 40-50% charge and 
I don't like to go below this.   is operating approaching 12 volts 
(transmit) really an issue?

David Moes
President: Peterborough Amateur Radio Club.
dmoes at nexicom.net
VE3DVY,  VE3SD

On 12/22/2014 11:31, Jim Brown wrote:
> On Mon,12/22/2014 7:05 AM, Greg Troxel wrote:
>> Jim Brown <jim at audiosystemsgroup.com> writes:
>>
>>> I run a contesting station with two K3s driving power amps with a 10A
>>> supply keeping the battery charged during the winter, and solar panels
>>> doing it during the summer.
>> What do you do about the voltage being 12.5ish instead of 13.8? Run the
>> K3s at reduced power (because of the amps you are doing anyway)?  Don't
>> worry about extra IMD?  Use a DC-DC converter to get 13.8V?
>
> Most of my contesting is done either at legal limit, with the K3s 
> driving an amp or at QRP. For NAQP, of course, i run 100W. Even at 
> 100W and 12.5V the K3 is pretty clean, and at the 40-50W level it 
> takes to drive my Ten Tec Titans, even cleaner. The measurements in 
> the link below were taken with my usual power setup.
>
> k9yc.com/P3_SpectrumMeasurements.pdf
>
> Someone mentioned using a solar charge controller. I'm using a GV MPPT 
> charge controller between my solar panels and the battery. It's RF 
> quiet. Most charge controllers make RF noise. GV makes several models 
> for different battery types, voltages, and current ratings. They are 
> available here. The company also seems to be a good place to buy Li 
> batteries.
>
> http://www.batteryspace.com/140w-10a-solar-charge-controller-with-mppt-for-lithium-batteries.aspx 
>
>
> 73, Jim K9YC
>
> 73, Jim K9YC
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