Re: Why more power-efficient at or below 3 W?
Posted by
Rick M0LEP-2 on
Jan 27, 2021; 12:38pm
URL: http://elecraft.85.s1.nabble.com/KX3-Why-more-power-efficient-at-or-below-3-W-tp7667847p7667878.html
That'd help to explain why I was able to eke a last QSO out of a fading
battery by winding the power down (as mentioned in an article in this
February's RadCom). It was the only SOTA summit-to-summit I managed that
day, too!
Of course, next time, I'll try to remember to charge ALL my batteries
properly before setting off up to a summit, and then also put them ALL
in my pack....
On Tue 26 Jan Wayne Burdick wrote:
> There are two windings on the PA output transformer: 1:1 and 1:4. We
> select one of these based on power level, battery voltage, and in some
> cases, operating mode.
>
> In the 1:1 setting, the PA drain impedance is 50 ohms, making it more
> efficient for at power levels, reducing current drain.
>
> In the 1:4 setting, the PA drain impedance is 12.5 ohms; the
> transformer steps it back up to 50 ohms for the low-pass filters. In
> this case it's more efficient at higher power levels, at the expense
> of higher current drain.
--
73, Rick, M0LEP (KX3 #3281)
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