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Let me start by saying there is no evidence that the situation I will describe is occurring or has ever occurred in a real QMX+. There is nothing here to worry about. It is most likely just something I am doing wrong so no panicking! OK, I have set up a model of the entire QMX+ lpf array. I have figured out how to make the diode model give a long reverse recovery (Vp parameter). The issue is not with recovery though. I am seeing something that is clear and yet must be wrong. The situation is that I have LPF4 enabled and the others disabled (by switching the gate of the correct BSS123). I set up my source to drive a signal big enough to generate 5 watts out, roughly 22 volts peak. I set up the sim to run without signal for 10 millisecnds to give the simulation time to stabilize the various voltages, mainly the time needed to charge all of the lpf shunt capacitors in the disabled filters up to 12-.7 volts. At that point I discovered that it is a bad idea to simply switch on the 22 volt peak input signal full blast because it ends up creating a large enough input to forward bias the unused filters input diodes. Once the diodes switch on, they cannot turn off until the input signal stops (28MHz period is way less that TRR of the diode). Switching on the lpf0-3 filters puts a near short on the PA output and kills any chance of the doubler getting the reverse bias up above 22 volts so it is fatal. OK, so maybe I need to "shape" the PA output. I "modulated" the input signal amplitude with an RC charge and here is where I ran into the issue. If you do the math on LPF0 capacitors (4400 pf total) charging through a 470k resistor, it takes 5 milliseconds or more to charge. What I found is that I had to use 5-6 milliseconds of "shaping" on the startup of the input signal in order to avoid tripping the LPF0. This seems too long to me but it looks like it is the way it is designed. Note that these diodes are OFF and get turned on by the large input. This has nothing to do with TRR (which is for ON->OFF transitions). This seems to mean that filter input amplitude transitions that rise above 12 volts must do so SLOWLY. Everything in the model seems to be doing what it should. The doubler doubles and the bias begins to rise when the input approaches 12 volts amplitude but it rises at different rates on the load side of the six 470k resistors with LPF0 being very slow and LPF6 being much faster. I have to raise the input amplitude slow enough to avoid turning on the LPF0 input diode. So, where am I going wrong? I have never used a PIN diode but I THINK I understand how they are supposed to function as switch. Is there something that keeps them from turning on quickly? Again, this is SURELY a red herring. But I would really like to make this work right so I have to ask. Thanks, Tony AD0VC

Everything has gone textbook right for my QMX+ (kit built) for a few weeks now, but I knew it couldn't last. I was receiving with the USB connected to a Raspberry Pi 4 running WSJT-x and it seemed to be working fine. Then I looked back and the display was dark. Pushing the startup knob drops the regulated voltage to 11v and current limit of 600+mA, which goes back to zero mA when the push knob is released. No idea what happened, but it's down to the basement "bench" to take a look. Film at 11..... -- Brent DeWitt, AB1LF Milford, MA

The wiki page QMX QMX_plus Debugging has been updated by @Ludwig_DH8WN <DH8WN@...>. Compare Revisions

Greetings all, I am currently assembling a Rev 3 QMX+ and have a question regarding T501. When it comes to continuity between an A point and a B point, my DMM (a Fluke 12) does not beep, though it does display '2.006' on the screen. If I switch the meter to measure impedance, measuring from any A point to ground or a B point results in the meter showing a resistance of 9.77k ohms. Is this to be expected? Note: when I was separating out the winding leads when winding T501, there was NO short-circuiting between the primary and the secondary. I appreciate the help! Charles Johnson PS While I don't think that it would make any difference, for the record, L502 has already been installed, but the BS170s have not (I'm going to socket them, which means that it's easier (at least for me) to install T501 first).

Greetings to the brain trust. I have a kit built QMX which is awesome and works great on CW. I have upgraded to the 1.02.000 ( the latest firmware) and added a QRP GUYS mic. Everything seems to check out in the hardware tests, but it seems very low output on SSB. I've set the mic. gain to 75 which seems to help, some. Any ideas on trouble shooting? Thanks in advance. WX7J Doug

I recently purchased an assembled QCX Mini. I absolutely LOVE this transceiver and I have been using it everyday on W1AW for code practice. I also copied the instruction manual and put it in a neat spiral spine, including a sturdy cover and I keep it beside my transceiver at all times for reference. Soon I plan to go on the air. My problem is, the way to program it is not sinking into my elderly and challenged brain. I'm sure the manual is written well but I often have problems understanding technical instructions so this, by no means, is a problem with the manual. It is instead, a problem in how I process information. Has anyone out there created a "cheat sheet" with step by step instructions? Example: Step 1, Do this. Step 2, To save your setting, do this, etc. Thanks in advance for any advice or "cheat sheet" you can provide. 73. .

Could someone please explain to me a simple, quick, non-fiddly way to send a signal that my T-1 tuner can use to tune itself? I tried searching the forums but didn't find anything. Thanks all.

Rev 3 QMX+ running WSJT-x 2.7.0. When running with USB audio mode (SSB mode on QMX+), selected in both the QMX and WSJT-x the TUNE/TX ENABLE or PTT test only gives a momentary PTT signal the first time, try again and it keys the QMX+ correctly. In digi mode in both WSJT-X and QMX it works 100%. Anyone else seen this please? 73 Ken g4apb

Enjoy https://www.youtube.com/watch?v=bsDBcFXgHbY 73 DE muhsin TA1MHS

My parents got me the QMX 80-20m kit as a present for getting my license in Australia. This is my first time doing something like this but the challenge was very fun here are my problems- 1. when the case is off, the radio will turn on but half the buttons don't work properly and the screen is so bright that I can hardly see the text. eg turning up or down the right-hand knob will always increase the frequency or setting number. The right-hand knob also won't click down and no settings are saved upon restarting the radio. 2. when the case is on, the radio draws power (about 0.3A at 12V) but only when pressing down the left-hand knob, after letting go no power is drawn and it stays off. I have looked over the instructions and schematics several times, just want some advice on how I can fix this. Thanks VK3AUN

We had eleven folks join the MI QRP Zoom Chat on 22 May. Please join us Thursday May 29 (and every Thursday) at 4PM Eastern for the Michigan QRP Club weekly QRP Chat where the main topics will be QRP and other ham interests. New hams are encouraged to participate and ask questions. It's fun, it's easy, and it's free. You only need a computer, a smart phone, or a tablet that can connect to the Internet. OR if you can't be close to any of those you can join by audio with any standard phone. Just follow the directions below. No software needs to be loaded or installed. Anyone can join and non members are welcome. Details are here: https://www.miqrp.net/zoom Zoom ID: 811 0835 6229 Pete WK8S Ed AB8DF Ernie NE3TE Tony W8CDC Stan WB8QJZ Casey KC9IH Larry AC8YE Dave N8SBE Harry K9DXA Randy KE8JWB Charlie NJ7V It was Randy’s first time. Welcome. Ernie purchased one of the new palm paddles at Hamvention. He was able to convert it to a kootie key. It was Charlie’s first time. Welcome Harry was at FDIM and did POTA on the way home. Both Ed and Ernie got a bunch of SMA connectors and cables because they got a WB2CBA Pocket Tuner at vendor night which uses SMA. Ed also got a ADX Pocket. The ADX is an Arduino based Digital Modes Transceiver. Stan wanted to know if we were able to get a look at the new Ten Tec rig. Yes there was one but we could not get a real close to it. It looked like a very rough prototype. We were also able to see the new Yaesu but just too many people to get close. There was a new Flex Aurora. Pete is going to do a Move-In special contest when this relocation is complete and has his shack up and operational. Standby for details. Dave has a AI6YM T41 kit https://ai6ym.radio/store/ We talked about the I and Q on a KX2 vs I and Q on a QRP Labs QMX QRP. Lab 599 has a new radio based on the Wolfe transceiver. The Elecraft K2 has an accessory that will do digital and one that will do a panadapter. Dave is working on doing a K4 remotely. The K40 is Elecraft’s top priority. Ekecraft is also working on a better noise reduction. The topic for Thursday, 29 May will be Field Day. The agenda for the 29 May QRP Chat: Ernie to do a short introduction and acknowledge any new folks to the Zoom chat. The topic for next May 29 will be Field Day. During the open forum anyone can take the floor. We will go one by one until all have had a chance to have the floor. Files, pictures and presentations can be shared if you have any. Please try to stay muted when someone has the floor. Thanks Ed AB8DF