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2.Assembling the FAA-450 Antenna Analyzer(EU1KY) - include some DH1AKF mod, KD8CEC mod (modified 18/may)

This document will continue to change as we make changes or additions.

If you have an antenna board, you can make your own antenna analyzer in 30 minutes.
also, you can buy assembled finished products.
If you have purchased a finished product, just follow the modifications below.

This document was changed on March 28. In order to prevent mistakes due to different output lines for each RF board,
Piezzo connection, RTC connection, Battery voltage connection.

mar/26 version for developer (my developing environment)
added power, rtc, piezzo, s2 port, and changed wire color for vi, vv -> left, out

I am planning several series about the EU1KY antenna.

5.Principle of Antenna Analyzer
6.Antenna Analyzer Firmware Improvement

Again, you can purchase the finished product by referring to the link below. 

1.Make FAA-450 Basic

It is the preparation for making AA. Simple, right?

You must first change the jumper on the Discovery board.

Below is a picture before work.

Remove the SMD resistor connected to SB3. SB5.
Connect SB1. Connect SB4.
Below is a picture of the work completed.

Wrap the cable around the core as shown below. I used an SMA connector for the experiment, but you can choose M, N, BNC type and so on.
You can also adjust the cable length to suit your case.

Connect the above prepared coaxial cable as shown below.

Below is a picture I worked on.

The middle of the coaxial cable should be connected to GND.
Using a knife makes it easy to work with.

Three wires are required as shown below.

Connect three wires to GND, V, I of the RF board.

Connect the opposite side of the wire to the MIC input of the Discovery board as shown below.

Be careful of the color of the wire being connected.

If you change between VI and VV, you can do a new calibration.

Congratulations!!!, You've created the best Antenna Analyzer with 15 soldering points.

2.DH1AKF's H/W Mod
DH1AKF introduced a modification to attach a speaker and RTC to the Antenna Analyzer.

I do not need to install the RTC yet, so I will just install the speakers. 
But later, if I add WSPR or FT8 functionality to Antenna Analyzer, I think I need RTC.
I connected an additional RTC

Prepare a speaker or Piezo Speaker with little wire.

I prepared it as follows to attach simply.

It will be connected on PI2 of Discovery board.

Below is a picture I worked on.


Connect the appropriate voltage to the RTC board. (I use 5Volt, so I connected it to 5 pin number. If the board uses 3.3Volt, connect to pin 4,
The data signals of A4 and A5 should be 3.3v signals. You should choose RTC carefully.)

The pin arrangement below is based on the RTC board I purchased. Please check the SDA, SCL, GND and VCC written on the RTC board.The remaining pins do not need to be connected.

Voltage Sensor
The voltage sensor uses PF8. I have been struggling for a while with the source code being marked as PF9, but it was the wrong library.
PF8 is correct.


Please refer to the following article for hardware modification of DH1AKF.

3.KD8CEC's H/W Mod (1st)
I would like to try Antenna Analyzer a little more fun. this is first mod

Connect and Coaxial Cable are required.

Connect the prepared cable to the RF board as shown below.

If for some safety, add a 10n to 100n capacitor for DC-Block. According to several beta testers, even if using 10n ~ 100n, | 21 | Gain measurement is not affected.

Completion. Easy?
You can install the built-in battery here, or you can connect an external battery for your mobile phone.

You must change the jumper below when connecting 5Volt directly to the board.

4.KD8CEC's H/W Mod PTT

Option #1

Option #2

5.K8CEC's Connect Transceiver and AA's Speaker Jack


  1. Is it not better to make input filter to second port like original input port?

    1. Thank you for your suggestion.
      Now I just connected because I see only strength. It is recommended to connect one capacitor for safety.
      I am confirming that I can see the phase of the signal from Port S2. If you can check the phase of the signal from Port S2, some additional circuit will be added.

      Ian KD8CEC

  2. He Ian,
    Can you tell me what ferrite core type you use (the RF choke) when you want the analyser
    to analyse up to 600 mhz. or higher ?


    1. FTxx-61 will do a good job as it has blocking properties from 200-600 MHz. FTxx-43 will be close to that, beter for low frequencies (up to 400 MHz). Usually, the ferrites from the VGA cables will be ok. 73!

  3. Replies
    1. This comment has been removed by the author.

    2. Looks like DS1307 is NOT working proper. I had to make some more testing about this. DS1307 can be a substitute solution for those who already have in the junk box some spare Arduino RTC boards. Also I replaced the 4558 with LM2904.

    3. I can confirm, the DS1307 is not working... Maybe Ian will take into consideration to add a serial TTL GPS for watch sync... Or make some modifications to the code to work with DS1307... 73 de YO3HJV

    4. I don't understand... I connected a DS1307 to I2C. Power supply to 3V3. I tested the board on an external Arduino and it works fine. The address is 0x68 just like the DS3231. On the AA it is not working... I have the 0.71 firmware. Any advice please?

  4. Tnx Adrian for your answers.

  5. Please use the DS3231 instead of DS1307. I did not make a program for DS1307.
    DS3231: It is tested and has better precision.


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