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Re: Questions about adjusting QDX RF output by changing supply voltage

 

Hi Charles.

Mine is built for 12 volts like yours. I usually run it down at 9 or 10 volts input while doing something like WSPR (1-2 watts out) and it doesn't get very hot. I run it at 12.0 or maybe slightly reduced (11.0) when?running FT-8 (approx. 4 watts out) and again no big heating issues. I am probably overly cautious compared to some.?

Yes, you can adjust the supply voltage while it's powered up. I would caution you to try not to do something I once did. My power supply goes up to 35 volts or so and I quickly discovered once I had adjusted the 10s of volts setting by mistake. I usually adjust the 10ths of a volt setting. I had it at 30 volts for 3 seconds while receiving and fortunately the regulators and all survived. I don't recommend testing yours that way :-)... good luck ...

73 ... Ron

On Fri, Aug 12, 2022 at 9:57 AM Charles Johnson <cjohnson@...> wrote:

Greetings all,

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I've no wish to stir up the debate about which supply voltage QDXs should be built for, but in reading the manual, I saw where it says that the power slider in WSJT-X has no effect on the QDX and that any RF output reduction should be accomplished by lowering the supply voltage. So...

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1) For those who have done the 12V build and adjust the supply voltage to change the RF output, what problems (if any) have you had?

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2) Is the QDX tolerant of supply voltage change while powered up or do I need to turn it off before I make a change?

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An example of why I would want to reduce the RF output is that I normally run ~1W when operating as a WSPR beacon, yet I usually operate FT8 at 2.5-3W, sometimes going up to 5W.

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I appreciate the information!

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Charles Johnson

KF4AYT
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