Ham Radio Maker

Signal Generator

ron@venaura.com (Ron) — Wed, 11 Aug 2021 18:17:19 +0000

I played around with building an Arduino Nano version of a Signal Generator. The project is on the brown prototyping board. It uses an AD9833 board (upper right on proto) and a 1.3 inch OLED display (lower left on proto). Two momentary switch buttons are connected to digital inputs on the Nano. You can also see that the oscilloscope is reading quite close to the programmed sine wave frequency.

I read about the project in an instructables.com posting by Peter Balch. Please note: What is shown above is wired to different digital inputs and was easily changed in the 'ino' file provided on Peter's page. (https://www.instructables.com/Signal-Generator-AD9833/).

My uBitx v5 Build

ron@venaura.com (Ron) — Sun, 28 Apr 2019 15:59:20 +0000

Starting my uBitx build. I am using an EF01 case for my unit.

Schematic of Step Attenuator

ron@venaura.com (Ron) — Sun, 14 Apr 2019 21:46:34 +0000

Searched online to find some schematics of step attenuators and then edited schematic into QUCS.

Simulator result

Volts	Expected DB	Calc DB
5
4.46	1	-0.99
3.55	3	-2.97
2.52	6	-5.95
1.26	12	-11.97
0.403	22	-21.87
0.0675	42	-37.39

The +20 db step is off quite a bit.

Make a Programming Cable for a Yaesu FT-4X

ron@venaura.com (Ron) — Sun, 14 Apr 2019 20:44:59 +0000

I referenced this video to modify a Baofeng cable to make a programming cable for a Yaesu FT-4X.

Pulled 3.5 mm audio pin out of cable

Pulled out 3.5mm pin

Open case at USB end of the cable gently with small screwdriver. Pry at the cable stress relief end.
Watch this video (Yaesu FT-4X Programming Cable) and dig out the needed diode from your parts stock.

solder it up

Soldered diode between TX/RX (anode to TX)

Test the cable with programming software available at yaesu.com
Reassemble the case

Building an EU1KY Antenna Analyzer

ron@venaura.com (Ron) — Wed, 03 Apr 2019 19:00:46 +0000

So I got my Technician license April 2018 and wanted to get started in the amateur radio 2M band. Knowing that I would want to make a good antenna, I figured that I would need an antenna analyzer. I looked at the costs of analyzers on the market and decided to DIY. That’s when I found the EU1KY.

My assembled EU1KY Antenna Analyzer

I assembled the analyzer using the required instructions for the EU1KY open source project (EU1KY wiki page) after ordering boards for the RF unit (I have extra boards for sale on my Ebay Site).

Under the hood

Note: The RF front end board mounts onto an
STM32F746G-DISCO Development Board (available from Digikey.com for about $60). Under the connectors for the RF board there are some surface mounted jumpers. The board comes with them soldered onto SB3/SB5. Move them to SB1/SB4 and then check them for continuity. Check that SB3/SB5 are non-continuous.

Move jumpers on stm32f7-discovery board

Connect I, V and Gnd from RF board to blue audio on Discovery board like this.

For calibration, an Open/Short/Load (OSL) test kit is needed. I built mine from some spare SMA PCB board components. The 50 Ohm load has two 100 Ohm resistors in parallel and can be made more attractive by using 0805 SMD resistors. You could even do three 150 Ohm resistors in parallel to achieve the 50 Ohm target value.

Afterwards, I built a 2 meter ground plane antenna.

2 meter ground plane antenna

Measurment

Used analyzer to scan 144Mhz – 148 Mhz …

The results:

S11 graph

SWR graph

I welcome any discussion on this project. Just add comments below or email me at my arrl.net address (callsign ke0rje).