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1. Checking weather data packets carried on the APRS-IS
There are several types of weather data packets and they are identified by the character after the first colon. The most common type is the APRS Position Format identified by the at-sign "@". This type carries the station time, station position and weather data. Another type is the APRS Positionless Format identified by the underscore-sign "_". This carries station time and weather data. Station position is in a less frequent status packet. Yet another type is the Peet Format that carries the station time, station position and weather data in hex characters. This type is identified by the dollar-sign "$".
Here are daily records of each of these packet types. The first four sets are updated hourly and show the latest received packet and the number of packets and duplicates received from that station during the previous hour and since the start of the day. The last set is updated continuously and covers the past 2 hours.
- Ham operators using APRS position format (last 10 days)
- Citizen CW Operators using APRS position format (last 10 days)
- Citizen DW Operators using APRS position format (last 10 days)
- Ham Operators using the Peet hexidecimal format (last 10 days)
- Ham Operators using APRS positionless format (last 10 days)
2. Diagnostic Information for T238 Weather Stations
The T238/1-Wire weather station is a kit that is inexpensive, but still provides an very good, very reliable weather station. This kit has been built by numerous hams who use it to send weather data to CWOP. One feature is that this weather station also sends hourly diagnostic information through the APRS-IS.
Each line of these T238 diagnostic files is a diagnostic packet generated near the top of the hour. The diagnostic message is the part after "e1w". The first two numbers are the software version number. The error counts for each of the measured parameters are given by two hex numbers from 00 to 63 (sometimes 128). On the weather station LCD, these error counts are in decimal, but in the diagnostic message they are in hex. These two digit error counts cover temperature, wind speed, wind direction, rain gauge, and humidity. The last two digits are hex numbers that indicate the value of the buss voltage when things aren't changing. For a complete explanation of these diagnostic messages, go to the T-238 homepage above and select "project status" and then "debug message".
3. Equipment Information
For more information on these types of weather stations and the various subsystems, see these web pages:
- Home page for T-238 Project; where to get software
- TAPR; where to purchase a T-238 kit
- Dallas Semiconductor; information on 1-Wire Weather Station
- AAG; where to purchase a 1-Wire Weather Station
4. Wind Tunnel Measurements
Testing was carried out in a calibrated wind tunnel located at the University of Colorado to determine the conversion constant between the number of counts in a 5 second period and the wind speed in mph. Four different 1-wire anemometers were used to verify that there was not large unit to unit variation. Starting with the assumption that for a 3-cup anemometer the center of the cup moves at about 85% of the straight line wind (heard by a friend in a meteorology class years ago), a conversion constant was calculated and the measurements taken. This graph shows the indicated wind speeds for each of the four units. Then these measurements were normalized by the true wind speed and averaged to determine the average offset from the true wind speed. This graph shows the averaged normalized results. Then the conversion constant was modified to minimize this offset.
|Page generated on Dec 18, 2011. Site maintained by Russ Chadwick, KB0TVJ. Send any comments to Russ at wxqa dot com.|