MF (medium frequency) radars (MFR) are powerful tools for understanding the upper atmosphere, by measuring horizontal wind velocity and electron density. This article introduces three MFR systems, two in Japan, Yamagawa (31.20N, 130.62E) and Wakkanai (45.36N, 141.81E) radars, and one at Poker Flat, Alaska (65.1N, 147.5W). Experimental techniques, and their observed results are briefly shown. Horizontal wind velocity was observed by those MFRs, in height ranges of 60-100 km (day) and 80-100 km (night) at Yamagawa and Wakkanai, while the data coverage is unusually low, >54 km (day) and >68 km (night), at Poker Flat. Comparison of MFR winds with temperature observed by a collocated Rayleigh lidar at Poker Flat shows consistency of those two instrument results in terms of atmospheric wave theory, implying validity of MFR data at such low altitudes. Electron density results at Poker Flat agree reasonably with International Reference Ionosphere model values at 74-84 km, and agree well with variation of cosmic noise absorption by the Poker Flat imaging riometer, suggesting valid electron density estimation by MFR at least below 80-85 km.

A priming effect is studied for a three-electrode, surface-discharge AC-PDP, which has stripe barrier ribs of 0.22 mm pitch. It was found that by keeping the interval between the reset and address pulses within 24 µs, the data pulse voltage can be reduced while the data pulse width can be narrowed due to the priming effect. By adopting the primed addressing technique to the PDP, the data pulse voltage was reduced to 20 V when the data and scan pulse widths were 1 µs. Alternatively, the data pulse width could be narrowed to 0.33 µs when the data pulse voltage was 56 V. 69% of the TV field time could be assigned for the display periods with 12 sub-fields, assuring high luminance display.