[Elecraft] New KX3 Owner: Power Supply Question

[Don Wilhelm]

Jeff,

When you measure the output of the regulator with your DMM, you are 
drawing very little current.
However, the KX3 draws current from the regulator which results in a 
lower voltage.

Also the solar panel needs to be oriented toward the sun on a clear day 
to develop its full rated output, if it is at some other angle to the 
sun or the time is other than mid-day, you will have less output.
You may want to try using the solar panel to charge an external battery 
such as a Sealed Lead Acid type rather than trying to power the KX3 
directly from the solar panel.

73,
Don W3FPR

On 3/29/2014 1:44 AM, Thorpe, Jeffrey wrote:
> I’m a new KX3 owner - in fact, I’m pretty new to Ham and this is my first radio apart from an HT.
>
> What I’ve done is hooked-up a solar panel to it with a shunt regulator. The panel is rated for 18V and 18W, and my shunt regulator limits the output to 15V. (I have the battery charger/real-time clock option installed also, and the solar panel will charge the internal batteries.) With the KX3 on, it shows the internal batteries at 9.9V, and the PS at 15V. While I can set the transmit power up to 12W, it does drop to 5W when I try to transmit. This doesn’t really surprise me, as I expect the KX3 requires more current than the solar panel will deliver. The power supply voltage reading on the KX3 drops to 10.1V (while it shows the internal batteries still at 9.9V.) Oddly, even when I stop trying to transmit though, the power supply voltage stays at 10.1V. Unplugging the solar panel and replugging it does not change the reading back to 15V, it just goes to 10.1V when coming back off the internal batteries. When unplugging the solar panel, I take a reading with my multimeter and it reads 15V at the output of the shunt regulator, but when attached to the KX3, the KX3 still says 10.1V. I have a12V A/C adapter (only rated for 1A though) and if I plug it into the KX3 it reads 11.8V. (just to see if it might be a problem with the shunt regulator, I used it with the A/C adapter, and it did not appear to be a problem.)I then plug the solar panel back in and it says 10.1V again. So I leave the panel unplugged, monkey around with the KX3 and dig through Fred Cady’s manual for awhile, plug the solar panel back in, and I get 15V. Then the process starts all over.
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