Posted by
Mike WA8BXN on
Mar 07, 2011; 3:14am
URL: http://elecraft.85.s1.nabble.com/KX1-MAZX-supply-voltage-tp6095842p6096029.html
Was Re: [Elecraft] KX1 MAZX supply voltage
There has been much discussion about kits and homebrewing in another thread,
and the question about max voltage for a KX1. The KX1 is a fairly simple
radio, so its possible to start to analyzing the factors that would
determine max supply voltage. Of course, Don's suggestion (warning) that its
best to follow the manufacturer's value is the safest.
The portions of the radio that run on internally regulated voltages will be
safe if the regulator input is not exceeded. The regulator input limit is
pretty easy to determine. But its not quite that simple, as the voltage to
the regulator is increased, so is its power dissipation.
The remaining parts of the radio that get unregulated voltages would have to
be evaluated individually. I'm too lazy to look up the schematic, but I
suspect the final audio amplifier runs off the unregulated input. Again the
specs on the device would give info on how much the input voltage to the
radio could be. Nothing much fancy about that.
My greatest concern would be the output transistor in the transmitter. Here
things get complicated. The specs for DC voltage limits give an upper limit
to supply voltage. But since we have some inductance and tuned circuits
involved an AC analysis would be required. To further complicate things, the
antenna SWR would come into play. Not simple at all!
Once past the final stage, a look at the driver would be needed too.
Well that's a beginning to the analysis. Hopefully others can add some
comments and analysis. A lot can be learned from kits when you go beyond
just assembly. Is it the same as designing a rig from scratch? No, not quite
the same thing. But being able to really analyze design gets one close to
being able to do design work.
73 - Mike WA8BXN
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