EU1KY Antenna Analyzer Kit

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Recently, my local amateur radio club has been developing a DIY antenna analyzer (AA) based off the Jack Purdum (W8TEE) antenna analyzer that was featured in the November 2017 issue of QST. Based around an Arduino Mega 2560, the current design and specifications that my local club is attempting to expand the range from 1-30 MHz, of the W8TEE analyzer, to 0.1 - 500 MHz approximately. The goal is to cover not only HF, but VHF and UHF as well. It is quite ambitious given that we are trying to aim for around $150 price point and trying to get roughly the same, if not better, performance that the W8TEE analyzer.

This project has been ongoing since January of this year, and there have been typical engineering struggles and challenges (i.e. Fighting with CAD tools, Sourcing an inexpensive oscillator for this application, etc). Even though I bought into the project, I honestly got pretty impatient, so I started to look on my own at other DIY Antenna Analyzers that exist. Some Googling led me to the EU1KY Antenna analyzer design. This design predates the W8TEE design and appears to be quite popular and well supported by the community:

Many DIY Case variations
  

The Technical Review

This design predates the W8TEE design and appears to be fairly popular and well supported. At its core is the STM32F746G Discovery kit, which is a STMicroelectronics development/evaluation board for the STM32F746 microcontroller. This microcontroller is no slouch by any means; This board features a "High performance ARM Cortex-M7 32-bit RISC core operating at up to 216 MHz... It also implements a full set of DSP instructions". So lets put this in perspective... We have a 32-bit ARM microcontroller with DSP support running at 216 MHz, whereas the ATMega2560 is a 8-bit microcontroller running at 16 MHz and no DSP support. Let me put that in chart for easier reading for you:

I think it's fair to say that the STM32F746 Is far superior for this application.
W8TEE recommends getting a ATMega2560 Pro Mini from EBay, where they average around $10, whereas the STM32 board averages around $56. When we break this down the ATMega2560 costs $0.63 per MHz, whereas the STM32 board costs $0.04 per MHz! When it comes down to value the STM32 just kills the ATMega2560. On a side note if someone were to design an antenna analyzer leveraging the Raspberry Pi Zero W ($10) the cost per MHz would be a penny!

According to the official documentation, the EU1KY AA uses the DSP math libraries provided by ARM, so the software definitely does not let the DSP capabilities of the STM32 go to waste. This is important, because for a device like this you want squeeze as much performance from what dedicated hardware you have at your disposal.
The 32F746GDISCOVERY

It is also noted that in order to thwart the efforts of overseas manufacturers, the developers of the EU1KY insist on the tight and exclusive integration of the development board of from STMicro, because the computing hardware and display are shipped together with proper quality control and there are no known copycats of this development board. Also, if you carefully do some research on this development board, you will quickly realize for about $50-$60 that this board retails at (on Digikey, Mouser, Arrow, Future), it's pretty difficult to undercut the bill of materials (BoM), which STmicro kindly provide, without cutting corners and resorting to sketchy distributors. The display + Micrcontroller in single quantity costs $47! When you add in interfaces, connectors, and board design costs, this board becomes relatively inexpensive!  I respect this because of my personal dealings with fake, counterfeit, and copycat hardware. 

The development board that the EU1KY AA, also uses a far superior 4.3" capacitive touch screen, unlike the (In my opinion the worst and inferior) resistive touch screens. I think the only downside here is that this display is 48 pixels less than the 3.5" arduino TFT that the W8TEE design uses, but it's a worthwhile trade-off. 

The EU1KY AA, when connected to a PC with a mini-USB cable can be used remotely via the RigExpert AntScope Software. The device emulates some features of the RigExpert AA-1000.

The Kit Review


The EU1KY can be purchased as a kit from Elekitsorparts. I purchased option 2 ($145), options are explained on the bottom of the page, because I ended up buying the STM32 from a distributor for less and I wanted to assemble the kit. Option 1, is a fully assembled unit, but where is the fun in that?

The aluminium enclosure is fantastic and solid.

It is specified on the page that the frequency range is from 1-150 MHz, but I have personally verified that this device works up to 500 MHz with proper calibration, hence why the model number is AA-450, duh? It is noted on the page that the measurements are "less accurate" and it uses "3rd harmonics of both signal and local oscillator (LO) above 150 MHz", but basically this once again comes down to the STM32 eval board and software leveraging the DSP functions.

You need to provide your own 18650 Lipo battery (due to shipping restrictions), but you can basically get these for free, they are in many cheap power banks that are literally given away...






Conclusion

For less than $200 the EU1KY AA-450 Kit is a very capable and inexpensive Antenna Analyzer. In terms of performance per dollar this kit beats any 8-bit microcontroller based antenna analyzer. The sheer fact that the STM32 microcontroller has dedicated DSP hardware and functions, and that the EU1KY software utilizing them, cannot be overlooked and honestly makes any antenna analyzer based off the ATMega2560 look like a toy in comparison. In my opinion, the fact that kits like the EU1KY exist makes me wonder why other hams are still using 8-bit microcontrollers with no DSP hardware, it's 2018, not the 80's anymore...



Comments

  1. Please have a look at the software modifications from me.
    http://wkiefer.de/x28/EU1KY_AA.htm
    73, Wolfgang (DH1AKF)

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    Replies
    1. Thanks! I love your software mod! I think many hams in my club will buy this kit and run/modify your software :)
      73, Jeremy Hong (KD8TUO)

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  2. Any thoughts on how it performs once assembled? Couldn't find it on their site, but are schematics/source-code available if you wanted to modify it?

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    Replies
    1. Very comparable to the Rig Expert AA-600. The EU1KY is a better value for money though., and yes the schematics and code are available here: https://bitbucket.org/kuchura/eu1ky_aa_v3/wiki/Home

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