Re: Does QCX Mini have DIY emission indication function? #qcxmini


John Pagett G4YTJ
 

Alan,

You are right, that there can’t be a single ended indicator. But what the circuit diagram shows and what is reality can differ. Let’s assume there’s some capacitance to ground at the LED. To charge this capacitance, current would flow through one diode (with a smaller amount through the junction capacitance of the other diode). To discharge the stray capacitance, the current will then pass through the other diode, passing through the LED on the way.

I’m not saying that this is what happens, just that it’s a possible explanation.

Tomorrow afternoon happens to be a “do some electronics / radio” session over Zoom with a couple of friends. I’ll lash something up and see what results I get.

Pagett’s axiom - When reality and theory differ, reality takes precedence.

73
John Pagett
G4YTJ

On 17 Mar 2021, at 17:19, Alan G4ZFQ <alan4alan@...> wrote:



So chucking a "single ended" indicator to it is quite safe, it when you make it a "double ender" that it becomes a problem.
There can be no "single ended" indicator. If it indicates it is consuming power that has to be returned, just like an antenna.

I would think that any harmonics would be low but they could well be there.

73 Alan G4ZFQ





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