Re: Variable power control

Tim Gorman


What voltage are you feeding this with? I assume it is more than
24v in order for you to have a 24v position.

If you are running in the 10 volt position, for instance, that would be
drop of at least 24v - 10v = 14v. Fourteen volts at .5amp is 7W being
dropped into that transistor. That's a pretty fair amount of heat.

tim ab0wr

On Fri, 09 Mar 2018 06:17:16 -0800
"Walter" <> wrote:

On Wed, Feb 21, 2018 at 06:23 pm, LKNDAVE wrote:

i did the hokie pokie and this jpg came out

Based on this design I built this attached circuit.

It controls voltage nicely.  Really helps limit output power while
working digital.

However the TIP 142 really generates some heat.  I have a heat sink
on it but it will need to be much larger.  it is only drawing
about .5 amp (1/2 amp) while transmitting.

Does that seem normal?  it the heat something I should be concerned
about?  Or just provide a better heat sink and run it?

Thanks for the circuit idea and plan.
73, W9KJO

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