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I have a couple of the 3.3V ONLY display boards prebuilt and I want a couple of volunteers to test them out. They have to be: 1) people with working radios, and 2) have displays that misbehave (meaning if you move them around, elongate the cable, etc… the processor locks up). I don’t really have the problem so its hard for me to fully evaluate if the display driver boards completely solve this issue. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

I looked at pin 24 on Tweensy, Daudio-Out that goes to U5 audio processor. There is a signal there but it does not look any thing like a digital signal, I do see an occasional spike that coinsides with pulse I hear in headphones. Anyone ever looked at the D-Audio output from Tweensy with a scope to see what it looks like? Tim W4YN

A couple comments on Rob’s talks… there are plenty more of them in addition to these. Rob has done a wonderful job of evaluating radio transceivers… I’ve been to his house/ lab and he has the perfect location for his evaluations. He will always give you an honest evaluation answer but never recommend a radio. He does have some peculiar operating habits, like all of us, that causes him to identify waterfalls and knobs that he likes… that might not be your cup of tea. In the past 5+ years Rob has been on an SSB IMD tirade, pushing predistortion accommodations with the top commercial radio manufacturers. It’s all good stuff but he tends to extend that to the builder and hobbyist level at times that doesn’t always resonate with some of us. In any case, he does tout using class-A final RF amplifiers in the transmit stages of radios because they, by shear design, will generate less IMD. If any of you want to join the “Class-A” club, my 20W and 100W amplifiers will operate in Class-A operation. The amps have plenty of head-room in terms of dissipation to perform this task, but at a reduced power and efficiency. My original PA designs contained hardware to adjust the bias to perform this, but I was worried that people would try to keep the PA at the 20W level while in this pseudo class-A operation at about 28% efficiency. Now will this be of use with the T41… hmmm that is left to the reader. I will publish instructions on how to put the 20W PA in class-A operation by readjusting the bias. Have fun with this but also have a extra set of transistors laying around! Expect about 5 watts out for a safe level of performance. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

I see lots of test points on the RF board, is there a list of expected voltages and signal data for each point somewhere? Trying to trouble shoot my RF board issues. Tim W4YN

Yeah and make sure you do it with the attenuator at ZERO! THEN go ahead and calibrate the RX attenuation control. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

I didn't say that right. The calibration of the s-meter sets the ZERO point (well... -73 db point) on the meter. That is the intercept of the equation for "S" units. You also have to calibrate (eg determine) the SLOPE of the curve using the attenuator (because we know the attenuator is correct). S-units (an any input) = S-meter calibration point at fake -73 db + "Detected signal strength in S units above zero" So above S=0, "Where Detected signal strength in S units above s=0" = gain(S=full scale - S=0) * received signal strength in fake dbs. You need to set the attenuator at two different points to resolve the slope. This is very crude so don't kill me... just fix it... Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

I was just doing this for one of my other radios, and wondered: Is the S meter display on the T41 calibrated? S9 is defined as -73dBm, or 50 microvolts @ 50 ohms. I think I'll try it out with a signal generator. - Jerry, KF6VB

I’ve never had noise from an on-board source, but that doesn’t mean it couldn’t happen. There is probably a solder bridge somewhere that is causing this… but keep it simple… to hone in on the area of the circuitry with the issue. Oliver had some good input… if the clocks both look good… you can follow a calibrated input into the receiver front end… past the transformer (TP4), then past the attenuator and the gain stage (TP6)… if all that works there is only the mixer U1 and the filters at TP5 and TP3. Here is another great diagnostic tool that a lot of people forget about. You can take the RX I/Q output at J1 into your computer through the stereo input… load a SDR program like SDR Console and demodulate the signals as if it were the Main board. [Note: this also means that with the addition of a simple software subroutine/ control module to the suite of existing provided modules in any of the SDR PC programs, anyone could build only the RF board and have a fully functional QRP Transceiver. Other boards could be added to additional functionality]. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

Hello, This has very little to do with the T41... I have this homebrew linear. It interfaces with my T41 quite nicely. Just like the T41, it has a Teensy 4.1 inside. Bands are chosen using Yaesu "BCD" band codes. Four wires, each one can be "high" or "low" gives you a four bit code and 16 possible bands. The standard is that "high" is near 5V, and "low" is near 0V. Just like in the old TTL days. The Teensies, however are 3.3V devices. Any inconveniences are compensated by the fact that they are WAY faster than any 5V Arduino. When I built the linear, I converted the 5V ( from an FTDX10 ) to 3.3V with a resistive voltage divider. When I built the T41, I converted the 3.3V from the Teensy to 5V using an open-collector transistor switch in each line. The problem with this is that the noise immunity is not good. So when the linear starts transmitting, RF gets into the band-chooser lines. The linear changes to a different band, and the protection circuit then says "Oh you have the wrong LPF", and shuts off the power. I *love* that protection circuit. I am still on my first MRF1K50. No amount of bypassing fixed it. I have bypassing and RF chokes at the T41, I have bypassing at the linear. I shielded the cable between them. I mostly fixed it by saying "We never change bands during transmit, so ignore those lines at that time". How to know that we're in transmit? Software on the Teensy monitors the drain current of the MRF1K50. If it's greater than zero, we're transmitting. But for some reason, it still does it on 10M if I run more than 800W or so. Doubtless RF starts coming out before the Teensy notices the drain current.... I guess. ANYWAY - the recent discussion about level shifters intrigued me. Is there an IC solution that's better than open-collector drivers and resistive voltage dividers? One that has decent noise immunity? It does not have to be fast; these lines are essentially DC. - Jerry, KF6VB

This one will work for operating the display at 3.3V and 5V. It’s about $0.60 more that the strictly 3.3V driver board. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

No. data line voltages at 3.3 and VSS to the display requlator of 5V... Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

Oh brother, this is starting to get complicated. The RA8875 is a 3.3V chip… and the inputs, as far as I can tell… from my research so far… are only 3.3V tolerant. To make this more confusing, some of the display.com displays have level shifting hardware onboard that you can enable to use the display as a 3.3V display or as a 5V display (in line with the power selections on the MAIN board). However, not all do (particularly the smaller displays). The boards I made work with 3.3V and 5V display boards… which is fine for 3.3V operation for all display boards…. The problem comes if you select 5V operation bon the MAIN board… but either don’t have a 5V control line selection on the display board for level change to 3.3V for the RA8875… or if you DO have the level change hardware on your display board but have not selected it. In this case, you will destroy the RA8875 chip. I can do two things. One is to put together a list of all the approved Display.com display part numbers (upper middle of the back of the display) and give guidance on what you need to do so that the display continues to function with this driver board. The other thing I can do is make a second board that has a tiny 3.3V regulator on it to power the three control lines to just 3.3V in the case of running the display off 5V but no hardware is there for level shifting the data lines to 3.3V. Comments? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

Well fact is… I’ve already done that… sort of…. For my prototype, I installed a 2x4 socket in a 2x5 holes pattern on the PCB knowing full well that 2 of the 10 holes on the end of the 2x5 connector are N/C. However, good news! I was able to find 10,000 of them surplus for a very low price. They will be here next week. There is another issue I discovered. The ISO7241 SPI driver chip has two forms… an “M” form and a “C” form. Here is the difference: “The devices with the C suffix (C option) have TTL input thresholds and a noise-filter at the input that prevents transient pulses from being passed to the output of the device. The devices with the M suffix (M option) have CMOS VCC/2 input thresholds and do not have the input noise filter or the additional propagation delay.” For electrically operating it won’t make a difference. What might make a difference is the noise filter in the “C” version and I have not explored that (eg only have used the “M” version. I suspect the “C” version may work better for people in high EMI situations. So I’m gonna make a few of each… send them out to a few folks here with finished radios and see which works best for them. Unfortunately, I don’t have a high EMI location… so for me testing them may not be a fair comparison. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...

With one or two exceptions… I’ll put together kits for the display driver. I can even have a few of them built for those who want a finish product (my daughter-in-law is a stay at home EE who needs something to do. She has built stuff for me before). One thing… I need some help finding the part in the attached diagram at a reasonable price (like it should be about $0.15 max each)… it’s a 10 pin female socket, 2x5, PCB mount. Tayda has 2x4 and 2x6 but not 2x5 for whatever reason. Digikey and Mouser are sky high. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. email: bill@...