View Single Post
Old Oct 12, 2012, 02:40 AM
srnet is online now
Find More Posts by srnet
srnet's Avatar
UK, Cardiff
Joined Dec 2008
3,651 Posts
Some info for Morse skeptics;

As part of the project for the satellite version of this beacon I had tested the line of sight range of the data telemetry between distant hilltops, the 100mW that the RFM22 can transmit was enough for reliable reception of packets at 40km.

At the time I made some recordings of the Morse audio also produced by the beacon, and have just been evaluating the results.

The recording of the beacon transmission, 40kM away was made with a FT60 with a 1/4 whip, with at each successive loop of the beacon software the power reducing. This made it easy to work out the limits of reception. The attached ZIP file contains a MP3 recording of the distant beacon at 12.5mW, 6.25mW, 3.2mW and 1.6mW. The last is very feint.

The FLDIGI software (free) running on a low spec PC Netbook will decode the 15WPM Morse down to 3.2mW, and 60WPM down to 6.25mW, which in approximate terms gives the faster Morse data a distance advantage of 4 times that of the RFM22 data telemetry, if Morse and data were running at the same power.

This should equate to a LOS distance for the fast Morse of circa 160kM at the full 100mW.

I have since been experimenting with running the Morse at 120WPM for the satellite version, and it seems to perform much the same as 60WPM, a slight degradation is noticed at 150WPM.

At 120WPM, the distance and direction is sent in 1.5sec, Latitude and Longtitude in 3.5secs.
srnet is online now Find More Posts by srnet
Reply With Quote