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The T/R switch, Q508, switches open during transmit, protecting the receiver circuitry. JZ

Hi Ryuji, My D109 was just "soft", having a high internal series resistance. It still began conducting at the proper voltage, it simply didn't conduct much current and allowed more than 5 volts to be

I need to clarify and apologize. Like many others, I often refer to VDD and VCC incorrectly even though I know the difference. I meant "VDD" pins on the MCU. There aren't any "VCC" pins (5 volts)

FYI zener diode very often fail in short mode especially when over voltages in small doses repeatedly or otherwise gradually.

One other thing, I tested transmit by sending a series of dits in CW - maybe 5-10 at a time. [email protected]> wrote:

From experience, I can say that it has done no damage. I'm running from an 11.5v supply, if that matters. Also TX testing was done with a dummy load. 73, Randy, KS4L [email protected]> wrote:

If someone were to transmit with T507 wired in the “U” configuration . . . would that fry the receiver? As in ruined beyond repair?

Hi, if it is QMX it is here: https://www.qrp-labs.com/images/qmx/manuals/schematics_rev1_a.pdf 73 Bojan S53DZ

Is there a 'proper' circuit diagram available? I've been searching this forum but i can only find 'bits and pieces'! Shane Doveton G0JNR.

Thank you for the starting point. My job took me out of town for the next day at least, maybe two, so it'll be at least a day before I can test it. I promise to update you on that as soon as I get

I had the same problem. Tracked it down to the MCU by eventually lifting each VCC pin on that chip (very carefully-I had to fashion a tool and use the big microscope) until the short cleared.

I have lots of wall warts.? I may be remembering wrong, but I thought there was an article or amendment on one or several of the install instructions on either a power supply filter or how to build a

JZ is correct about modeling the ferrite transformer/inductor. When looking at a well built Guanella transformer, the core material should influence on the loss and other fine detail properties but

Leland and all, The reason for that is tubes have high output impedance with some capacitance and the grid of the driven tube has a decreasing input impedance as well as a reactive structure

Oh, in case of push-pull, that P is for each half of the amp, so the actually measured/combined power would be 2P.

Power amp standard load line goes like this P = (Vdd - VDSsat) ^ 2 / (k * ZL) ZL in case of push-pull, 25 ohm when the output transformer is 1:1. k is usually between 1 and 2. Classes C/D/E/F is

When I first built my QMX, it had zero RF output and the RX could only barely hear the strongest signals. Mike/w1mt suggested I remove T507, bypassing it across its C-C connection and see what

Perhaps unrelated but on my first QCX+5W it started a WSPR transmission cleanly by degenerated to barely receivable with lots of noise wideband after minute or so This was totally stand-alone. ? I

Evan, Tony, Here are some VNA measurements posted by Tony AD0VC. They are in agreement with measurements I have taken. Measurements done where the winding parasitic capacitances factors strongly can

On Mon, Sep 25, 2023, 4:35 AM John Zbrozek <jdzbrozek@...> wrote: > Evan, Tony, > > "Correct inductor value" is not a simple question! > > The inductance of a core based transformer will depend