Wednesday, June 30, 2021

Economical 12 Vdc power supply

Purchased an Xbox 360 power supply at the thrift shop for a few dollars. It has a relatively powerful 14.2A 12V output.  It is basically a computer power supply in a portable ruggedized kid-proof casing. For the Xbox 360 there are 3 versions: 16.5, 14.2, and 12.1 amp.  Others have reported converting them to general 12V power supply use.

First step was to cut the factory dc plug off.  When you plug the power supply into AC power you will get an orange LED.  To enable the 12V output connect the red and blue wires together (the LED will change to green).  You can wire them together permanently or even switch it electronically and have a remotely controllable dc power supply.  

The voltage is a bit low @ 12.2V, but is acceptable and does not drop too much under load. As far as noise it is surely not in the same league as a proper (much more expensive) power supply. However, I have tested it briefly on the HF bands and was still receiving quite a few signals. It's definitely superior to other low-cost switching power supplies and 12V chargers I have tested. Should work great for VHF and above.  May not be ideal for 24/7/365 application, there is a variable speed internal fan which would probably fail after some time. Still, considering the cost, it makes a decent portable or spare/beater 12V power supply.

Xbox 360 power supply with 30A Anderson connector installed.  Noise on HF could be further improved by adding more impedance in addition to the single choke that is on the dc output cable from the factory.

Tuesday, June 29, 2021

APRS Weather Station

Added weather station (WX) temperature, % relative humidity, and barometric pressure data to APRS igate. As with most APRS fixed stations KL3RR-2 periodically sent a packet out containing a position and static "comment" which has now been replaced with (more useful) weather telemetry.

Reading temp + RH over RF (433 MHz) from an Acurite wireless remote sensor using an RTL-SDR and rtl_433.  Many other brands and models of wireless weather stations are supported. Barometric measurements are from a Bosch BMP 280 communicating with the Raspi through I2C bus.  

The pressure measurement is corrected to sea level barometric pressure and all parameters are fed into APRS client XASTIR through a "networked WX" interface using a combination of shell + python scripts and the network utility nmap.  (Inspired by


KL3RR-2 Raspberry Pi igate + WX


Bosch BMP280 absolute pressure sensor on Adafruit board in "custom" enclosure. Accurate to ±1 hPa / mbar. 


KL3RR-2 sending a WX packet (XASTIR on Raspberry Pi OS).

A week of weather data as presented by  KL3RR-2 sends out a WX packet every 15 minutes.    

This weather data can also be provided to the Citizen Weather Observer Program directly through APRS-IS.  Submitting WX data to this program provides useful quality analysis which can help detect problems and improve the accuracy of the station.