U01 emergency communications antenna

Updated Version !!!! 27. August 2022:

This PCB is designed for FT140-43 core with 2 in 14 turns and should be able to easily handle 100W. Use 500V silver Mica Capacitor 100p. PCB has footprints for BNC and SMA Connector. The spool was designed a little bit bigger, so it would also carry the amount of wire, when using DX Wire FL ! I personally use UL (Ultralight) by DX-Wire.

Toroid, Capacitor and SMA connector soldered on PCB.
Cover in position.
completed Antenna
Just 307 grams ready to go…..

This updated PCB just replaces the broadband transformer PCB. Wire lenth etc all stays the same.

End of Update

The Antenna was designed, tested and published by DJ5RE (Tom). Within our DARC Chapter U01 this Antenna has been built multiple times and the concept is proven as very reliable and repeatable.

Introduction to the U01 Antenna and further explainations

I´ve used the same wire lengths as in Tom´s original article (including the loops to connect the segments together,) but I build my own specimen around a FT82-43 core transformer with QRP in mind.

This is the concept drawing:

Antenna wire was Ultralight from DX-wire

Rope was Polyester rope 2mm by DX-Wire

Connectors were 2mm RC connectors

Broadband transformer was wound on FT82-43

Transformer was wound with 0,63mm copper enamelled wire

This is one set of the required print files (printed in PETG at 0,15mm layer height, 3 shells, 30% infill)

Remark: The following PCB Files are not neccessary, when you use the U01 Spindle PCB (from top of this Page)!

You can use DG1JAN´s PCBs to built the 1:49 broadband Transformer:


Update 09.Sept 2022:

Jan has updated his PCB and has now also the Gerbers on his GitHub. To be sure to have the latest Revision, please download the Files from his Github.

End Update

And these are the Gerber files for my own PCB:

How to wind a Broadband-Transformer and the theory behind it is explained here: