Re: K3 battery power
Posted by
hank_stamper on
URL: http://elecraft.85.s1.nabble.com/K3-on-Order-tp5299937p5321688.html
On Jul 20, 2010, at 9:00 PM, Wes Stewart wrote:
> Joe took the words right out of my mouth.
>
> Personally, I use an "unnecessary" boost regulator when on battery
> power or a PS set to at least 14V otherwise.
>
> [snip]
> Unfortunately, this does not apply to transmit IMD. Since the K3
> (like all other solid state transmitters) has a fixed ratio broad-
> band transformer between the final FETs and the 50 Ohm output.
>
> As the voltage falls and current increases, the amplifier impedance
> changes (decreases), the final amplifier operates into an increasing
> mismatch and the IMD becomes worse. Keeping the voltage to the
> final amplifier as high as possible within its specification allows
> the lowest possible IMD and highest efficiency.
>
> 73,
>
> ... Joe, W4TV
>
Interesting. I run a K3 off a couple of pseudo deep cycle 12 volt
batteries with an Iota smart charger hooked up. I run mostly digital
so IMD is important to me. The Iota runs between 13.1 and 13.6 volts
by my K3's meter. Would the difference between that and 14 volts make
a meaningful difference in the IMD ? What brand and model booster
provides 14 volts? The MFJ promises 13.8.
TIA
73 de Eric, KG6MZS
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