[Elecraft] Power Suppy for K2

[michael taylor]

On 10/2/06, Samir Popaja <Samir.Popaja at impact-europe.se> wrote:
> Which to choose, switching supply or not switching?

I would say choose based on how you plan to use it. In a roomy radio
work area a linear is nice and simple. It can also heat the room which
is nice in Canadian winters. If you have a tiny area or will often
move / carry the power supply you will likely want to choose a
switching power supply.

I personally have a 23A 13.8VDC Samlex model 1223. I've used it on
both 120 and 220VAC with no problems. It requires an easy but many
adjustment to switch input voltage so if you want to use it for
international travel look for a model that works with any input AC
voltage. Just about any will handle both 50 and 60 Hz with no issues.

> Whats the difference between switching supplies and not switching supplies? Pros and cons...

The main factors are size/weight, efficiency, and RF noise.

Switching power supplies are lighter and sizer for equivalent power output.

Switching power supplies are more efficient at converting AC input to
high current regulated DC output 80%-90%+ efficient versus about
30-60% efficiency for linear PS. This causes the amount of heat
generated to vary based on the design type, the heat is a waste
by-product of the inefficiency.

Switching power supplies use a high frequency (20kHz - 2 MHz) in their
conversion process, these can cause harmonic distortion in the RF
frequency range unless properly filtered. I believe switching supplies
will always raise the noise floor due to the nature of how they work,
but I believe they can be filtered and shielded enough to make them
usable in all but the most demanding to weak signal applications.

> I'm wondering that ELECRAFT hasn't devoloped PS to match design for  K2 or K2/100?

Three reasons I can think of are: A linear supply is boring design
wise and very easy to home brew (as hard as a home brew QRP antenna
tuner) and a large transformer needed to power the K2/100 is heavy to
ship, and I suspect the economics were not attractive (Astron have the
majority market share of the US amateur radio market).

-Michael, VE3TIX