Archive for the ‘Ham’ Category.

Low cost sun shield for weather sensors

The white plastic radiation shields that protect the temperature, humidity and other sensitive sensors from any direct sunlight can be built for bargain. I started with trays from local garden shop. They sell for about 10 cents per tray with diameter 120mm (5 inches). About 10 trays were CNC machined:

shed1

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12V Power supply

12V high current linear power supply is very useful for HAM applications. I designed one based on s53mv schematic. The circuit is somehow odd because regulation transistors are in negative side of the current loop. Main reason for that is the collector or source of the transistors, which is connected to the housing of the transistor. To avoid isolation of the transistors from the heat sink it is better to have the housing, heatsink  and the transistors connected to negative rail of the power supply. It is similar to the car, where negative pole is connected to the chassis.

pcb pcb1

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Affordable pluviometer (rain gauge)

Today I started with realisation of some affordable weather sensors. First one is pluviometer or rain gauge. My idea is to attach some self draining container on the strain gauge. I salvaged one sensor from old kitchen scale (scrap from some other very interesting project).

First I drew my idea on paper:

IMGP0350

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3D printed Loop antenna

Branko, one of the famous experts for old(ish) radio devices designed magnetic loop antenna, which can be 3D printed. Here are complete instructions in german language:

Germany-Flag-iconLoop Antenne aus dem 3D-Drucker

Slovenia-icon Slovenski opis (in Slovenian language)

Mini CW Keyer / QRSS beacon V1.1

I designed dedicated PCB for the CW keyer. The project is very similar to the version made on prototyping board.

keyer pcb

Here are the updates:

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Programmable CW Morse Keyer / beacon

Mini USB dongle with STM32F0xx is suitable many for simple, mini projects. I attached speaker to Timer14 PWM output (Pin PA6) and LED (or optocoupler connected to PTT) to GPIO pin PA0:

beacon

The provided software is based on USB Virtual Com Port (VCP) device. The setup is done with command line interface using terminal from any PC. The setup is stored in the internal flash and PC is not required for normal operation. The mini beacon keyer can be used when powered with 5V.

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Simple small QRO for HF

I followed the ARRL Homberw challenge 50 watt aplifier entry. It is low cost, simple HF linear amplifier designed and built by the author as an entry in the ARRL’s 2009 Homebrew Challenge contest.  The requirements of the amplifier were: 40 meter band 50 watt output amplifier intended for use with a QRP transmitter as driver (less than 5W), constructed at a total material cost of not  over $125.00.

I redesigned author original design an put it on the double sided PCB with additional output banpass filters. I started with first prototype:

IMG_8924

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Prototyping with PLL ADF4351

ADF4351 is very interesting PLL chip with many features. Here is prototyping board to start playing around with this interesting chip.

adf4351

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MODEM, parrot, CAT, …

Full bunch of wires is hanging from each HAM station and PC connected to the station: CAT, audio, each via dedicated interface for isolation or level shifting. Additional mess is with parrots or digital interfaces for digital mode. I wanted simple solution, which can be conected to PC via single USB cable.

I was looking for simple audio CODEC and found WM8731. To have enough processing power for some simple DSP audio I chose cortex M4F microcontroller. There is also micro-SD on the board for audio recording and playback, two mini-DIN connectors with YAESU pinout and galvanic isolation for USB. I stareted this project few months ago. I will add posts when I will make progress with module programming.

modem

The PCB is 80x45mm.

Here is schematic: modem

And PCB layout: lingva

 

Stay tuned for further progress reports.

 

The software will be published on git.

Add weather report from local weather station to APRS node

I recently set up a APRS gateway. Check instructions in older posts. In the script pymultimonaprs you can set weather when set in a json-file. eg: “weather”: “/path/to/weather.json”. I live next to the automated weather station for our city. Instead of building own WX I decided to use the data from this nearby station. The data is provided in XML from our national agency ARSO. The data is available for some major cities in Europe, too.

Main idea was to prepare PHP script to parse the XML data and prepare text file, which is acceptable for pymultimonaprs. Next step is to wget this text from some server and copy it to the raspberry pi with cron job.

This page will give you an example how to:

  • parse XML file with weather data using PHP script
  • output the text for pymultimonaprs weather file
  • prepare cron job with raspberry pi

m117

 

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