Saturday, October 25, 2014

Ultimate QRP DX: 4M Moon Mission!

China's recent effort to send a spacecraft to the moon has had a nice benefit for VHF ham radio.  Attached to the last stage rocket is a radio transponder developed by LX0OHB, that outputs a 1-watt signal in JT65B mode on 145.980 MHz USB.  The transponder sends repeated callsigns, messages, voltages, temperatures, and has an on-board experiment monitoring space radiation levels.  More information is at the 4M website.  The spacecraft was launched 10/23/2014, will briefly orbit the moon on 10/27, and then will return back to earth on 10/28.

I was very surprised to find out that my small EME station (two 7-element VHF yagis and a preamp at the mast) was more than capable of reliably decoding the telemetry from this spacecraft!  Capturing a QRP (one watt) signal from over 300,000 km away is pretty remarkable.  I use exactly the same setup as I do for EME, and also run the 4M Data Delivery Client to automatically send the received packets from the 4M back to their central data warehouse.  Seems at this point in time there are around 30 stations providing the warehouse with live feeds of packets coming down from 4M as it heads towards the moon!

The keplerian elements for tracking 4M seem are near the bottom of this post: and the current position of the spacecraft is shown on their webpage at (for doublechecking your own tracking software).