A Periodic Switching Technique to Compare Antenna Performance in the Presence of Strong Fading

There is a strong and fast fading on HF bands. When testing my phased array with small active antennas, the measured front-to-back (F/B) ratio is usually between 20 to 40 dB with local stable signal sources with vertical polarization. The real signals coming from the ionosphere are with undetermined polarization. The signal levels are also unstable and at the RX output the combined effect of polarization and level changes are with a range between 5 to 30 dB. It is difficult to estimate the F/B ratio on sky wave signals since the fading effects mask the effect of F/B switching. Manual switching and S-meter readings are very unreliable methods to obtain accurate measurements. A setup to measure accurately the signal difference between F/B directions of a phased array or between any two different antennas is represented. The idea is to toggle periodically to the receiver input the two signals under test and display on the screen the signal strength graph as a function of time. It is much easier and accurate to obtain a reliable measurements of signal difference on such a display since we have a periodic process and also we can monitor the changes of this difference . Read more ……. http://www.lz1aq.signacor.com/docs/antenna-performance/switching-technique-compare-receiving-antenna-performance.htm