EU1KY Antenna Analyzer Modifications
This page is a description of the modifications I made to the open source/open hardware EU1KY antenna analyzer project.
The FAA-450 Antenna Analyzer is built from a STM32-F7 Discovery board, a small RF board consisting of 2 direct conversion
receivers fed from an RF bridge and a battery/power management board. The analyzer uses DSP techniques to analyze
the 10kHz IF audio output from the direct conversion receivers to compute the complex voltage and current applied to
the antenna port. From this, an OSL (Open/Short/Load) calibration is applied to give a complex impedance value for the antenna.
From this impedance, VSWR may be calculated when referenced to 50ohms (other reference impedances are also supported).
Kits or a built project are available from
This project originated from the EU1KY Antenna Analyzer V3, which features a 4.3" colour TFT LCD,
capacitive touch screen, HF/VHF(UHF) frequency coverage, built-in TDR function, signal generator function
and multiple scanning curves for impedance and VSWR measurements. Full open source software is available at
Development is by cross compiling for the STM32F746 board on windows (Embitz IDE) or
linux (makefile with arm-none-eabi-gcc). The generated F7Discovery.bin file is uploaded to the
device using ST-Link loader from
A hint for uploading: the device must be powered on and a mini USB cable must be plugged into the ST-LINK
port on the device. Also, I ended up using a windows box for flashing the device as there are some reports
that the linux version of ST-Link does not support the STM32F746 discovery board. For windows,
you will need to get the STSW-LINK004 utility and STSW-LINK007 windows drivers from the above link.
6M vertical scan on smith chart
The signal levels are low (0.1 to 0.2vpp), but do radiate when attached to an antenna!.
Using the generator mode and a frequency counter, one can adjust the internal crystal calibration factor to get
the generator accurate within a PPM or so. Tapping on the frequency display opens an onscreen keypad where a new frequency in
kHz may be entered. Steps of plus and minus 500kHz, 100kHz or 5kHz may be activated by pressing the onscreen row of 6 keys under the
frequency display. Several lines of diagnostic information are displayed that can be used to troubleshoot the hardware receivers,
the OSL calibration and the VSWR calculation code. One can also perform a screen save to aid in debugging.
Reformated Signal Generator screen
TDR scan showing both metric and imperial lengths
SWR scan of 6M vertical
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