Technical Topics > The RF Workbench
U-LULU (Updated LULU) for 48 meters, 20 Watt Class-E AM Transmitter
Charlie_Dont_Surf:
A friend who lives in Europe asked me to design a small transmitter. He has a supply of FT-243 crystals from "the before time" and wants to use them on a small transmitter. I hadn't done much with crystals in years but after doing a bit of looking around, I started looking at the venerable and often used LULU design.
As I looked, there were a number of things that bothered me about them and I could see that there was quite a bit of “low-hanging fruit” that could be easily “picked off the tree” (improved) without a huge effort. In the end, I decided to redo and modernize the LULU for him, making it an updated LULU, i.e., the “U-LULU”. I have added a commercially-available Class-D audio amplifier to make a complete AM transmitter with approximately 20 Watts carrier power output (80 W PEP) in the 48-meter band. This is better than the original LULUs, where output is reported to be in the 10-to-15-Watt range. I decided to publish this design to make it accessible to others.
I regard this as an entry-level transmitter, suitable for those with less building and electronics experience. For the SMD haters, I have purposely used a through-hole TO-220 transistor and larger SMD components. Most capacitors are at least Imperial 1206/1210 [Metric 3212/3225] though there are some 0805 [Metric 2012] components.
Complete write-up is here: https://app.box.com/v/ty24asdfjAEF00
Gerber files zip archive is here: https://wetransfer.com/downloads/0415f9221a49b764d95fb207e143c59e20211205050846/d5a62f (See below for new links)
BOM is here: https://wetransfer.com/downloads/9a9d186b74de847f01f336f0f2ee4b0a20211205050536/9d12ab (See below for new links)
outhouse radio:
interesting
Charlie_Dont_Surf:
--- Quote from: outhouse radio on December 05, 2021, 2019 UTC ---interesting
--- End quote ---
I'm glad that somebody thinks so.
Anyway, there's more to come. I've have become interested in designing small MW/HF transmitters. I can easily improve the gate drive and perhaps get a bit more power output on a smaller board. The end result will make the SMD haters very unhappy but that's the way the cookie crumbles. :D
markoramius:
nice update
Charlie_Dont_Surf:
Apparently the links for the gerber files and the BOM (Excel .CSV format) are dead. Here are new links:
gerbers: https://we.tl/t-mEexddP14C See below for updated links
BOM: https://we.tl/t-mJj5yAScly See below for updated links
The link for the article is still good: https://app.box.com/v/ty24asdfjAEF00
All the links are completely anonymous for both you and me. I have no idea who is downloading any of these nor do I even know how many times they have been downloaded.
If there is interest, I can do a another version with a synthesizer input (in addition to the crystal), a better drive circuit (for higher RF power output) and a single power supply input for the whole transmitter (for simpler installation). It won't be a LULU anymore but I don't think anybody really cares about that detail. (I certainly don't.)
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