T41k Build Log
This documents some of my experience building the T41-EP transceiver https://groups.io/g/SoftwareControlledHamRadio/topics using the Four State QRP kit http://www.4sqrp.com/T41main.php. The T41-EP weas developed by Al Peter (AC8GY) and Jack Purdum (W8TEE) and documented in their book "Digital Signal Processing and Software Defined Radio". There is a large, enthusiastic group participating in the development in the group above and here https://groups.io/g/AmateurRadioBuilders/topics and a group for this version build here https://4sqrp.groups.io/g/T41/topics.
4SQRP has this disclaimer on their web page:
This is a complex kit designed to be an experimental platform. I takes some skill and prior experience to have a successful build.
If you are new to the hobby or kit building and looking for a cheap kit to get on the air, this kit IS NOT for you.
This is a serious warning. I have built more complex kits like a Elecraft K2, but that was professionally developed, packaged and well documented. I have also built rigs from plans like a Barb V1.02 uSDX, ordering PCBs and parts myself and built a slew of QRP Labs and HF Signals kits. I think that this kit will be a bigger challenge.
One aspect is the continual development that causes confusion about any statement made on the T41-EP, The 4SQRP appears to be a V11 with some mods and at the time this written V12 boards are available. Another is that supply chain issues caused some parts substitutions that are not always well documented.
For an image of the T41-EP and a list of features check out the 4SQRP link above.
The T41-EP is built with SMT components, which I am not fond of and not very good at. A big advantage of the 4SQRP kit is that the SMT parts are already mounted. I am grateful to 4SQRP club members that took the time to develop, package and ship the kit.
During this log please remember that this is not a commercial product, but a community project by amateurs for amateurs.
December, 2023. Opening the box.
Power Supply Board
Case on left, PCBs on right. There are a few bags for specific boards and two large bags of the rest of the parts
This is a small board with just a few components but the build turned out to be surprisingly difficult. There are three part substitutions. Two were no problem, but the small PCB that replaced one of the linear regulators has pin functions in a different order. The builder's doc had confusing, redundant and incorrect directions. A revised builder's doc was clearer, but also wrong. I suspected an error so I looked up the pinout and then went to the builder's group to get confirmation. I later found a more elegant solution, but this one works. You can see the snarl of red wires under the small PCB.
After building I connected the supply PCB to my current limited bench power. No smoke. Next I tested the voltages at the handy test points. They were all good : )
Main Board
Main board parts
Cables put back in bag for now
Building set up
The larger purple board is the PMC1808 24 bit, 96 kHz stereo ADC and the smaller is the PCM5102 112 dB audio stereo DAC.
I decided to follow the advice of others and not mount the SMA connectors, which can go on either side, until I see how the boards are connected overall.
Almost done board
Although I have two Teensy 4.1s from other projects, they have "normal" header pins soldered on. The audio hat (on right) requires the Teensy to have long pin stacking headers for mounting. I have to either buy yet another Teensy or try to take the pins off without destroying the Teensy.
Image of Teensy with stacking headers for audio hat from builder's manual.
Got 'er done. I was able to remove the pins by cutting the plastic between them, heating and pulling out one at a time. Then I carefully cleaned up the holes and installed the long pin headers. Checking at the end, the Teensy is still working!
Here is the main board with the Teensy loosely inserted with its audio hat, the audio to board ribbon cable and fan mounted. I mounted the fan with "velcro" so I could later get to the Teensy SD card.
The encoders and switch matrix are next. There are 4 encoders and 18 push button switches for control.