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KIT-BUILDING: The T41: A New Kit-Building Endeavor
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kit building
BY JOE EISENBERG,
* K0NEB
The T41: ANew KitBuilding Endeavor
In the march to new technologies, amateur radio has gone from spark to tubes to transistors to ICs, followed by microprocessors and the latest technology, software defined radio, or SDR. The QRP Labs QDX digital modes transceiver is a great example of how far we have come in kits, having a pocket-sized SDR. With that leap in technology comes a tradeoff. The surfacemount components necessary to perform SDR tasks do not lend themselves to easy construction by the average kit builder.
In the Penntek TR-35 4-band CW transceiver kit, a lot of surface-mount parts are already installed as well as in the Four State QRP Group’s Nouveau75 75-meter AM transceiver. The QDX would be nearly impossible to construct at home if it wasn’t for having the surface-mount parts already installed. There are still a number of through-hole parts that need to be installed in all of these kits, and the new, yet-to-bereleased, T41 kit is a great example. This is a full-featured 20-watt SDR based transceiver with a color display and was designed by CQ Microcontrollers Editor Jack Purdum, W8TEE, and Al Peter, AC8GY. The Four State QRP Group, led by David Cripe, NMØS, is making this innovative radio available in kit form with all the surface-mount parts pre-mounted. Like my previous series of columns on updating the SB200 amplifier kit, this kit will be deserving of more than one column devoted to it. It isn’t often we hams are treated to such a high technology and featurefilled kit.
The T41 SDT (software-defined transceiver) kit is composed of seven boards assembled and installed as modules. The reason for this architecture is to add the ability to modify or upgrade each different section of the radio, including the firmware / software, without having to change a single main board. This process also breaks down the assembly process into stages and modules.
Unlike many SDR transceivers, the T41 does not require a PC. As you can tell by this point, this kit is NOT intended as a beginner’s kit or for somebody new to amateur radio. Nor will it be very inexpensive. This kit entails a lot of detailed work as well as a large number of interconnecting ribbon and RF cables to preserve the ability to make changes to the radio by modules. This radio is intended to become an “experimenter’s radio, ” one that the end user — if so inclined — can make into a continual project. The software will be open source and there will be more than enough spare room on the CPU module for changes and additional features to be added by those familiar with coding. The T41 is based on the Teensy 4.1 processor to perform both the FPGA (field programmable gate array) and control functions of the SDT.
A groups.io page has been set up to exchange information on construction of the T41 as well as user and designer-based updates and changes and software. It is at <https://4sqrp. groups.io/g/T41>. Because of supply chain issues and ongoing development, it may take a few months for this kit to be completely available and able to be ordered from the Four State QRP webpage. Meanwhile, the creators of the T41 have a book available through Amazon that thoroughly details the design and construction and operation of this radio. The book details how the radio was developed and covers how the software was developed as well. Search on Amazon for the T41-ep book to order it. Keep in mind that there will be some changes and updates from what is in the book as improvements are made in the kit to be distributed by the Four State QRP Group.
As I work my way through the beta test building process of this kit, I will present this work in these pages to cover this exciting new kit. I’ll show each module and give my hints and tips I discover along the way. The case was originally designed around using 3-D printed segments to form the case and has now been updated to using PC board mate-
*7133 Yosemite Drive, Lincoln, NE 68507 email: <k0neb@cq-amateur-radio.com> Hamfest Hotline #5855 T41 SDTprototype as shown at the 2022 Dayton Hamvention.
Alookinside aprototype ofthe T41. This testversion usedall3-Dprintedpieces to form the case. The T41kitinprogress uses PC boards to make up the case.
rial as is done on many other kits, especially many Four State kits. I’m going to start out by assembling the pushbutton matrix control panel used to perform a lot of functions without having to go through menus. Some of the photos in this month’s column were taken of the original prototype T41, which utilized 3D printed case parts. I will show the newer PCB based case parts as I assemble the kit in future columns.
Getting Started
The first board I assembled is the switch matrix board. This board holds 18 pushbuttons and is used to select most often used functions like bands, etc., quickly without using a menu system. This is probably the easiest board to assemble, but I’ll see as I progress through the kit. I put them in a row at a time to minimize the chances of any getting put out of position while soldering. Each row of three buttons totals 12 connections to solder. The main thing I noticed is that you need to ensure that the buttons are inserted fully and flat against the board to ensure the plastic stems all face perpendicular, making sure the supplied
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