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Ok, confession time. I am not an electrical engineer. I am a mechanical engineer. This might be important in that my understanding may need corrected by folks who are much more knowledgable. :) First

Hi Charles, Please see the U3S Assembly Manual what to add to the PCB and how to connect things and for the jumpers. At least you will have to insert one BS170 to allow the signal CLK0 to come to the

Ron, of course you are right about the current protection of a BSS84 in the QDX.? It is now about 61mA instead of about 11mA.? But this current limit is used only if one does a short to GND during

Hi Will. Probably best to go ahead with Bojan's suggestion and parallel a 100R across R10 in the QDX to raise the PTT eying voltage. Hope that solves it for you .. .73 ... Ron

And Will, have you measured the voltage over the series of 470R and the red LED? 73 Bojan S53DZ

Hi Will, generally I prefer using the active zero Ohm PTT line, as I said.? And I will do it in due time. 73 Bojan S53DZ

Hi Ron, No I did not do those precise voltage measurements, however I did a simple test when I was first trying to use the QDX PTT to trigger the PA.? I noticed that in that case the power did not go

I measured the voltage at the red TX led on the amp trigger by the QDX. It was only 0.89 volts. The voltage on the red TX led on the amp triggered by the QCX Mini was 1.94 volts. … Now, what is the

Hello Hans and all, I built the QRP Labs Si5351A VFO/Signal Generator QCU Ver. 4 for use in a Kenwood TS-520SE, for replacing the Kenwood VFO that lacks frequency stability. I have a single 60 meter

Hi Bojan. Interestingly, I breadboarded the keying circuit including the Red LED and resistors and there is still something like 3.3 volts available to the gates of the two BS-170 switches in the PTT

Yes, that would certainly work, but I needed to be able to turn off the power completely by remote control (this was so that I could switch to using an SDR receiver instead of the QDX over the USB

More later. Multi-year class reunion inside my old high school today Dublin High School, VA ( Dukes ) Class of '70 here. Lettered in varsity track- can only walk fast these days. 73, Bill, N4QA

Sorry again, quicky fingers on a mobile phone... Hi. Just wanted to conclude that's why I prefer an active 0 Ohm PTT (inactive = open circuit) instead of an active +5V PTT (inactive = 0V).? QDX is

... just to add... The reason for the 100R parallel to 470R is actually the PTT input in the 50W PA, which is over 470R and a red LED in series tied to the GND.? This way those +5V from the QDX is no

Hi, This is what I have done to get the reliable PTT trigering of a 50W PA from the QDX.? The reason is that the QCX's PTT is a direct logic output with either 0V or +5V level whereas the QDX PTT is

I would add using a dummy load to reduce RFI as an issue. 73 Evan AC9TU

Will, Note that the QCX+ rev 1 has the PTT signal on the TIP, and the others, including the QDX, have the PTT on the RING of the 3.5mm jack.? If you are using the same cable as a rev 1 QCX+, then it

Hi Wil. It sounds like something might be loading down the 5 volts. You should find a way to measure that voltage while transmitting with the QDX PTT connected to the amplifier. I recall reading a

Hi Peter, Sorry, what I meant was to use only one Grove MOSFET board, to supply 12V to the QDX when it's on. When that one MOSFET board is off, the QDX is powered by the string of diodes. Put them in

Too keep is short, QDX Rev 3 with the 1.04 firmware is providing 5 volts to the ring of the PTT cable, but not triggering the QRP Labs’ 50w Amp. ? What should I be checking? more details: - ?QDX