NEC model of the quarter size G5RV

Fractional G5RV antennas seem very popular in the US market, and they appeal to hams wanting multi band performance in small space.

One of the offerings is the quarter size G5RV, commonly marketed as the G5RV Mini.

The original concept set out by G5RV was a combination of a centre fed dipole and open wire transformation section to successfully deliver a lowish VSWR(50) on several of the pre-WARC bands. This enabled arbitrary length low Z feed extension to the transmitter, and allowed direct attachment to transmitters of the common design of the day (1950s). Continue reading NEC model of the quarter size G5RV

WSPR version confusion

Investigation whilst developing Evolution of WSPR revealed some potential issues relating to certain WSPR versions.

The WSPR 2.0 manual states:

Please note that messages with compound callsigns or 6-digit locators will not be properly decoded by WSPR versions earlier than 2.0. Further details on message formats can be found in Appendix B, and in the WSPR source code.

So, lets mine some data. Continue reading WSPR version confusion

Evolution of WSPR

WSPR (weak signal propagation reporter) is a system for recording on a central database, ‘spots’ of transmitting stations by receiving stations.

It is interesting to examine the contribution by transmitting and receiving stations, for without both, the system cannot work.

I downloaded the archive for December 2015 and did some basic analysis to explore the pattern of use on the 40m band, my main band of interest. Importantly, 40m provides opportunity for local, intermediate and long distance propagation though long distance paths might be restricted to just several hours on most days.

Screenshot - 1_01_2016 , 9_16_26 AM

The chart above shows that the T-index was near normal on most days, and 6 days it was quite poor, so propagation conditions during the month will be a little depressed. The effect on 40m is mainly on short ionospheric paths, say 50-500km. Continue reading Evolution of WSPR