Posted on

T41-EP Wiki

This preserves the Reddit T41-EP community Wiki. It is mostly focused on the 4SQRP T41 kit and isn’t being updated. I doubt the Reddit page will disappear, but who knows how Reddit will treat low activity communities as they seek to increase profits.

T41-EP Wiki

My goal for this Wiki is to consolidate the available T41-EP version information for building, modifying, and testing the SDT. Just considering the number of messages regarding the T41 over on groups.io, this will likely be an aspirational goal for some time and may never be fully realized. In the meantime, hopefully others find some use for what I’ve documented here.

I’ve searched SCHR messages backwards for “power supply” from 12/3/2023 to 6/17/2023. Will continue at 6/10/2023 when I get a chance.

I’ve searched SCHR messages backwards for “main from 12/5/2023 to 5/16/2023. Will continue at 5/14/2023 when I get a chance.

Hardware Availability

  • 4SQRP has a limited number of T41 kits available. Sales are currently paused to allow the kitter to catch up with shipping previous orders. When this is done, sales will be opened for the remaining kits. I expect these to go fast. The original group was sold in less than 8 hours. The best way to snag one is to join the T41 Support Group (see link at top of linked page) and keep an eye out for an email announcing that sales are open.
  • The 4SQRP kits are sold out. A second run is possible.
  • Need help identifying what is in your kit. This message may help.
  • Bill Schmidt is collecting orders for V012 boards as well as other T41 boards he has developed. See T41 Board Count 120523.pdf for the current list. You can email him at bill@wjschmidt.com to be added to the list. Specify the type and quantity of boards required.
  • This is the commonly recommended display to purchase. Select the Pin Header Connection-4 wire SPI interface, and ER3304-1 font chip options. The original spec was to get the 3.3V display but some found the 5V version was better for the radio (mods required). The display can be switched after the fact to either voltage with a solder jumper. Touch and SD card options are per your preference.

Module Discussion

These link to the main post discussing the particular module.

Hardware Versions

(This section will be updated as I work through the book and reflector. Ultimately, I want to list the changes to each version so I know where my builds stands.)

There are several hardware versions of the T41:

  • V010
  • V010 boards – 6/12/2022 version
  • V011
  • V011 boards – zip file, uploaded 7/20/2022
  • V011 boards – individual files from 7/11/2022
  • fixed a few errors in the V010 boards source
  • V012 – revision nearly complete
  • K9HZ “Differences between the T41 V011 and V012 – Main Board” document. Includes a brief summary on how to convert an earlier version radio to V012.
  • calibration automated
  • power control full range and attenuated
  • solid flat-gained MMIC front end
  • new hardware CW filtering
  • receive RF control and bandpass ability
  • source
  • new RF board source
  • Differences between the V011 and V012 board sets
  • Re: V11 vs V12
  • Re: T41 V010 vs V011 though this is more V12 vs V11
  • some discussion of V012.2 board performance here
  • Audio preamp and power amp provided by stand-alone audio amp, pg 165
  • receive hardware functions combined with excite functions and Si5351 clock generators on a single PCB, pg 167
  • (source: Revised T41 book)
  • 3.3V and 5V power supplies moved from power supply board to individual boards that use that supply source
  • Jumper on Main board selects 3.3V or 5V display source
  • 4SQRP kit – based on the V010/V011 boards with some mods by David Cripe (NM0S) source. While schematics and Gerber files for the kit aren’t online, the schematics in the Assembly Guide appear to be for the kit.
  • Re: Difference between v11k and v12
  • Re: Difference between v11k and v12

Hardware Board Version/Date

Based on file versions linked above.

BoardV010V011V0124SQRP(1)
Main05-30-2207-12-2212-16-2302-28-23
Receive06-01-2206-01-22NA02-12-23
Exciter06-01-2207-11-22NA02-11-23
Filter2022202206-06-22
Filter Relay06-01-2207-13-2201-30-23
Pwr Sup06-01-2207-05-22NA01-30-23
RF PA06-01-2207-11-2203-09-23
EncoderNANA2022
RFNANANA
Switch Matrix06-01-2207-11-2206-06-22

Notes:
(1) All 4SQRP kit boards are version V009b except the Filter and Switch Matrix boards which are V009a). The Encoder boards do not have a version number.

(2) V012 Main and RF boards are still in development.

Other Hardware Modifications

Consistent with its intent, the T41 has been modified by users beyond the hardware versions discussed above. Below are links to some of the modifications I’ve come across. Unless noted, it’s unclear at this point whether any of these modifications have been included in the official versions of the boards. Note that some of these just note an issue that may be resolved elsewhere.

  • SDT Hardware Modifications google doc with mod list by board. Not sure if It’s been kept up to date. The document is mentioned in T41 Experiments that called on builders to list the changes they’ve made, I believe for consideration for including in V012.
  • This message by K9HZ discusses V010/V011 Hardware Hacks and Updates.
  • QSD2 – improved receiver performance, particularly on 10m. This is likely the modification discussed in this topic which states the V010/V011 hardware is too slow to function on 10m. Thus, the 4SQRP T41 kit working on 10m is more aspirational than reality (or has it been fixed for the T41k per this message?). This topic discusses a software fix that might solve the problem. Edit: My tests show transmit and calibration isn’t possible on 10m on an unmodified 4SQRP T41. This topic seems to confirm that. The solution is to replace U4 and U5 on the QSE and QSD boards with 74LVC74A. I haven’t tested this modification in my T41 yet.
  • QSD4 – similar to qsd2, seeking to improve performance by running at 5V; here is a video showing the board in action.
  • Some builders are using a 5V display to minimize touchscreen noise source
  • There is some discussion on groups.io of heat produced by the 3.3V regulator. These messages here and here discuss adding multiple 3.3V regulators.
  • This message discusses sourcing the Switch Matrix 3.3V supply from the Teensy 4.1 rather than the power supply board to get more reliable switch action.
  • This message discusses adding a MCP 23017 multiplexer to the Switch Matrix to increase switch reliability (see KD0RC GitHub in Useful Links for code changes). K9HZ has created a board for this, source.
  • This message without context notes a change in power supply capacitors. Need to track down the mentioned post.
  • This message discusses removing the display buffer chip on the main board and running the wires directly from the Teensy to the display to eliminate display problems.
  • 20W PA module available from K9HZ,
  • 100W PA module available from K9HZ.
  • Component alternatives discussed 3.3V regulator alternatives as well as alternatives for other components.
    G0ORX T41 Wiki – Interesting Front Panel alternative with Raspberry Pi Pico controller.
  • More memory can be added to the Teensy Audio Hat source. It may solve problems previously noted as caused by processor overload source.
  • Add battery for real-time clock source and doc.

Software Versions

At the time of writing version 49.2 was the most recent version of the T41 software. On November 27, 2023, version 49.2K was uploaded for the 4SQRP kit version. Based on a quick review on the sketch file, it appears that the kit version is more than a simple edit of version 49.2 to make it compatible with the kit hardware but includes bug fixes and other features planned for a future release. This is an example of what happens when not using a better versioning platform, but pretty much par for the course with this project.

Johnathan Burchmore has created a GitHub repository with the T41 software. Previous versions are available as tags.

Version T41EEE.0 T41 the “T41 Extreme Experimenter’s Edition”

This message over on shows how to load an already compiled hex file to the Teensy. This could be useful for those having trouble compiling the T41 software. I’ll upload a hex file for the T41k software to my GitHub when I get a chance, probably after the holidays.

Software Modifications

User software modifications often get rolled into the main code base or even result in a hardware fix. The latter can leave builders using older hardware behind. I haven’t focused much on this area yet, but plan to expand it in the future.

4SQRP T41 Kit Anomalies

I found the 4SQRP T41 Kit (T41k) to be well kitted but there are a number of kit components that deviate from the original design. None of these affects the usability of the transceiver. I assume these arise from either supply chain issues mentioned in the Assembly Guide, product availability changes over the long kit development period or attempts to keep the cost of the kit low. I’ve not included deviations from BOM, as it appears that the BOM available in the Assembly Guide at the time the kits were first sold wasn’t entirely accurate. If you haven’t received the components listed on the BOM with your kit, let the kitter know by email and he’ll send the parts to you, or explain the deviation. Lastly, these are based on my kit. Your kit may differ.

  • Power Supply Board
  • LM1117 3.3V regulator replaced with OKI-78SR-3.3/1.5-W36-C buck regulator which requires modification to fit the footprint on the PCB (note that the 12/6/2023 Assembly Guide instructions for installing this regulator are incorrect. See the Power Supply post for more information on how to install it correctly). The new regulator has a high efficiency and doesn’t need a heat sink. Thus, the heat sink originally planned for the regulator on the PCB is not included.
  • The FQP47p06 MOSFET is replaced with a IRF5305 MOSFET. This seems like a like kind replacement due to availability. The FQP47p06 is listed as out-of-stock at several suppliers.
  • The 10 uF filter electrolytic capacitor for the 3.3V regulator was replaced with a tantalum capacitor, apparently because the LM1117 datasheet recommends it. This was done in spite of the regulator change that according to its datasheet doesn’t need additional filtering.
  • The diameter of the screw supplied with the LM7805 regulator was too large for the heat sink. I was able to screw it through the hole though with some force.
  • Main Board
  • The connectors on both fan cables are too large for their corresponding connectors on the Main board. They are also the wrong pitch, 2.54mm vs 2mm. The kitter says in this message that if requested he’ll send out a pigtail with the proper connector that can be spliced onto the fan cable.
  • Receive Board
  • I’ve never seen magnetic wire insulation come off while winding a toroid before.
    When winding the T1 transformer I noticed that the enamel insulation on the wire included with the kit was flaking off a bit with each turn. While the flaking wasn’t enough at this point to cause a short, given Jack’s report of faulty enamel coating on a transformer causing his IRF510 to blow up, I decided to be cautious and use my own wire.
  • Exciter Board
  • The 2-pin header, J5, is labeled J3 on the PCB.
  • PA Board
  • The holes for R202 and R205 on my board were not properly formed. The Assembly Guide says these holes on some boards may be “clogged” and must be cleared. I used a 0.8mm CNC drill bit to clear the hole and verified continuity between the top and bottom pads.
  • Filter Board
  • With the parts supplied with the kit, it’s really only practical to mount the daughter filter board to the back of the filter board without going to extremes as mentioned in this message. Up to now, I’ve considered this to be more of Assembly Guide issue which I’ve avoided for the most part in this Wiki as I assume they’ll resolve themselves at some point. However, it’s really more of a kitting issue as per the schematic the daughter board should be mounted to the front of the filter board. The filters on the daughter board are all symmetrical except the 10m filter (perhaps at one time they were all symmetrical, but if so, that was before the 4SQRP version). The reason I’ve included this as an anomaly now is that 4SQRP didn’t consider that a front placement was impractical with the components supplied. Whether the reversal of the 10m filter in the circuit will cause an operation issue or if the two toroids should be swapped is being discussed in this topic.
  • Front Panel
  • The Switch Matrix board is similar to the V010 board which has a few differences from the V011 board: (1) some of the switches in columns 1 and 2 are not aligned and (2) switches 17 and 18 are not connected. Without modification, switch 7, the most out of alignment, will bind with its cap on. This topic discusses how to modify switch 17 and 18. Without this modification, the startup calibration routine cannot be run. This should have been noted in the Assembly Guide. This topic provides and alternate wire consistent with V011. If you have a steady hand, this could be simplified with a single trace cut diagonally across the junction between R16 and C2 so that R16 is still connected to switch 16 but not ground and C2 is still connected to ground but not R16 or switch 16 (I’m going to try this approach).
  • My Switch Matrix board had production extensions remaining at the top and bottom of the board. These must be snapped off or the board will not fit properly into position on the front panel.
  • The encoder tabs are too big for the mounting holes on the PCB and must be cut off.
  • My kit (and many others) shipped with mono audio jacks rather than the specified stereo jacks. While these were promptly replaced the replacements had 3mm long mounting shafts rather than the original 5mm shafts. This was insufficient to mount properly and my jacks tended to pop off when inserting a cord.
  • Chassis
  • The knobs are smaller than shown in the kit pictured on the 4SQRP website.
  • The power switch is smaller than shown in the kit pictured on the 4SQRP website.
  • The bottom mounting holes on the rear case panel do not align with the Boost Converter.
  • The mounting holes on the heat sink for the IRF510 transistors do not align with the PCB requiring the transistors to be mounted at an angle and the leads bent to properly solder them to the PCB.
  • At this point, it’s unclear how the fan will be mounted to the heat sink or how its cable will be routed to the case interior. Per the kitter, the 3.5mmx12 screws are included to mount the fan to the heat sink. These screws are too short for my fan/heat sink combo. Perhaps my heat sink is not formed correctly. The connector on the fan cable should be 2mm which would fit through the hole in the case. The kitter has 2mm connector pigtails that can be spliced onto the fan cable. Otherwise you’ll have to cut off the 2.54mm connector and devise a method of connecting the fan to a power source. The kitter sent me 2mm connector pigtails to replace the 2.54mm connectors on the fans. The kitter also sent four 37mm screws to attach the PA fan to the heat sink. Unfortunately, these screws are still too short by about 6mm and can’t be used. I’ll work something out myself, perhaps with a visit to the hardware store.
  • The chassis front feet cannot be attached with the screw/nut combo described in the Assembly Guide as the nut is too big to fit in the available area. It’s possible that longer screws were included to solve this, but it’s unclear at this point whether those screws are to be used elsewhere in the build. Edit: Duh. The front feet mount just fine with the screw head on the outside rather than the inside as shown in the Assembly Guide. That makes more sense given how the boards are mounted.
  • BNC connector on the SMA to BNC Bulkhead cable too big to fit through hole in rear chassis panel. I used a round file to enlarge the hole until the connector would pass through.
  • The audio patch cords in my kit were 9 cm rather than 15 cm as specified in the BOM. The 9 cm cord is too short to fit between the Receive and Main boards installed according to the Assembly Guide. Some users have just flipped the Receive board to allow using the shorter cable. Note that requires the power cable to be constructed differently than shown in the Assembly Guide though. I’ll probably just order a longer patch cable as I prefer the contemplated board orientation as it will better accommodate some mods I want to make (note that the kitter offered to order and ship a 15 cm cable to me).
  • The kit comes with a USB Host Cable to extend the Teensy 4.1 USB connection to the rear panel of the chassis. The rear panel end is a USB type A connector. More appropriate would have been a USB type B (or mini). As is, a USB type A to USB type A cable is needed to use the extension. This isn’t a common cable nowadays. I’ll probably just splice something together. Edit: I finally found such a cable in my stash. When I went to install the USB Host Cable I found that it’s not sized properly for the mounting holes on the rear panel. You can make do by attaching the cable with a single screw. Just another thing to add to the grab bag feel of this kit.
  • to be updated as I move through the build

Useful Links

Prepare Your Computer to Compile T41-EP Software

I’ve compiled the latest version of the T41 software, STDVer049.2, with version 2.2.1 of the Arduino IDE. I used the following steps to set up my Windows 11 PC.

  • Download the latest version of the Arduino IDE and install in according to the directions for your PC. I used the default installation setting. Note that this mingles libraries with version 1 of the IDE if it is installed. If this is a problem, you’ll need to make version 1 “portable”.
  • Add the Teensy 4.1 board, the T41 MPU, to your Arduino IDE. Download and install it from here. There is also a tutorial to check if you’ve installed it correctly.
  • The T41 software depends on several libraries. If you’ve worked with any of the authors other projects some of these may already be installed in your Arduino IDE. The required libraries are noted in the “Library include files” section of the T41 software SDT.h file. Several required libraries are available in the Library Manager. I had to add Etherkit Si5351. I already had the Adafruit GFX library installed but if you don’t you can install it with the Library Manager. The GitHub directory for some non-standard libraries is noted in the SDT.h file. You’ll need to download these to your library folder if they aren’t already installed (simply download the library as a zip file from GitHub, unzip it in your Arduino library folder and remove the “-master” extension from the folder name if present). For STDVer049.2, on my machine I only had to install OpenAudio_ArduinoLibrary and Rotary.
  • It’s possible that you have a similarly named library that will conflict with the one needed by the T41 software. I had this problem with the Rotary library. If this happens and you want to maintain the other library, you’ll need to make the earlier version of the IDE portable. This will place the libraries associated with your earlier IDE in another folder. You’ll then need to download the T41 version of the library as above. Note that the GitHub for the RA8875 library is noted in the SDT.h file, but a library with this name was already installed with the Teensy board on my system. It’s unclear to me if this needs to be replaced or not (it’s not noted elsewhere in the T41 “documentation” that I can find). The software compiles with the Teensy version, so for now I’ll leave it as is.
  • Download that latest version of the T41 software. If you’re a member of SoftwareControlledHamRadio, version 49.2K is available here. Otherwise, you can download a copy from my GitHub.
  • Test your set up by opening the T41 Arduino sketch (SDTVer049.2K.ino for example), select the Teensy 4.1 board in the dropdown below the menu bar and click the Verify (checkmark) button. Resolve any errors and repeat. Once you’ve compiled the software error free you can try uploading it to the Teensy. Mine uploaded without problem with the following note and the orange LED flickering slightly.
  • The Teensy memory may need to be erased before uploading new versions of the software. Do this by holding the Teensy program button between 13 and 17 seconds (I guess the timing is critical as my first two attempts to do this didn’t work). This will erase the Teensy memory and load the default blink program. A flashing orange LED shows the process was successful.

Opening Teensy Loader…
Memory Usage on Teensy 4.1:
FLASH: code:248884, data:124512, headers:8548 free for files:7744520
RAM1: variables:207360, code:245336, padding:16808 free for local variables:54784
RAM2: variables:368928 free for malloc/new:155360

Testing and Troubleshooting

  • This message over on groups.io discusses breadboard testing of the Teensy 4.1 and display.
  • T41 receiver spurious signals discusses tracking these down to the display running on 3.3V and various interactions on the main board.