Propagation News – 7 July 2015

| June 5, 2015

We are now truly into the summer propagation season in the northern hemisphere, which is characterised by lower maximum usable frequencies during the day, compared with winter, but higher MUFs at night. Solar activity has continued to be low, with a solar flux index of around 100. There have been no major flares of note this week and geomagnetic conditions have remained relatively calm.

At the time of writing the forecast for this weekend’s field day was for reasonable, settled conditions, an SFI of about 110 and a low Ap index of about five. If this pans out then it should lead to a good Field Day with F2 layer openings to the south up to around 21MHz with occasional Sporadic-E openings on 10m.

The eighth, ninth and tenth may see more unsettled geomagnetic conditions with a Kp index hitting five due to another recurrent coronal hole and its associated high speed solar wind stream. This may knock MUFs down considerably and bring auroral conditions.

VHF and up propagation news

Be on the lookout for good VHF propagation next week as both Sporadic-E and tropo look like delivering the goods.

Next week will see high pressure becoming a dominant feature on the weather charts. A large high will develop just to the west of Britain on Sunday and should remain nearby until the end of the week, when a small thundery low may spread northwards into the country from France.

It’s likely that there will be enhanced VHF conditions for some parts of the country until near the end of the coming week. The best direction to look will be along the axis of a ridge of high pressure extending propagation into northern Europe and the Baltic.

Sporadic-E continues to deliver, primarily because we currently have a strong jet stream over northern Europe, but as the high develops, the jet stream will be displaced farther north and openings into Europe may have to rely upon different weather triggers like thunderstorms and upper air ridge patterns. The high will mean less chance of rain scatter on the upper GHz bands than last week.

The moon reaches positive declination and perigee this week with consequent lengthening moon windows and low path degradation.

Category: GB2RS Propagation News