rjr@mgweed.UUCP (Bob Roehrig) (07/18/84)
qst de k9eui hr propagation forecast bulletin nr 29 from arrl headquarters newington ct july 16, 1984 to all radio amateurs bt the solar flux resumed its usual downward trend during the past week, moving from 101 on july 9 to 89 on the 15th. this range is slightly below the base value used for the propagation charts in qst for july 9, but not enough to make a significant difference in midsummer dx conditions. the state of the earths magnetic field is more important than the solar flux in determining the usefulness of our dx frequencies in midsummer. high geomagnetic activity narrows the useful rf spectrum and causes erratic fading and increased distortion on voice signals, especially on high latitude circuits. these adverse effects were very marked july 13 to 15. they will be in evidence often through july, though less than in the days just prior to the issuance of this bulletin. with the sun moving southward again, dx conditions will improve gradually over the next six weeks. the change will become most obvious in early september. american sunspot numbers for july 5 through 11 were between 52 and 82 with a mean of 65.7 ar
rjr@mgweed.UUCP (Bob Roehrig) (07/23/85)
qst de k9eui hr propagation forecast bulletin nr 29 from arrl headquarters newington, ct july 21, 1985 to all radio amateurs bt the solar flux curve is following a trend that began in may. early in the month there was a marked rise, followed by a sharper decline to very near quiet sun values. in the low period that began july 15, the flux curve is almost exactly superimposed on that for 4 weeks earlier. this trend is expected to hold, with flux values close to 70 until about july 27th, followed by a steep rise in early august. about half of the sun has been active and the other half almost quiet for the past 3 months. the active periods bring very frequent geomagnetic disturbances and unstable propagation. the calm, like the period now at hand, gives more stable conditions, but with lower muf. this should be with us through the rest of july, with more variable propagation again in early august. sporadic e layer ionization is now declining, so 21, 24, 28 and 50 mhz will be less active through the rest of the summer. a more direct relationship between solar flux levels and dx conditions will be apparent as we move into august, and increasingly clear in early fall. usefulness of the qst propagation charts will improve, especially where high latitude paths are involved. there is some possibility of better hf dx conditions in late 1985 than were experienced in the same months of 1984. that was a time of exceptionally low solar activity for less than 9 years into cycle 21. american sunspot numbers for july 11 to 17 were between 3 and 50 with a mean of 18 ar