Propagation News – 24 November 2019

| November 22, 2019

The predicted poor geomagnetic conditions forecast for late on the 16th didn’t amount to much. In the event, the Kp index rose to three before settling back down again quite quickly. The Sun remained spotless all week again as we get close to the minimum. As such, HF propagation was relatively poor all week.

Daytime critical frequencies have mostly been in the range 4.5 to 5MHz, which really prevents short range propagation on 40m. Thursday, the 21st, was the exception, when the Chilton Ionosonde recorded a critical frequency of 5.925MHz at 1130UTC, which equates to a maximum usable frequency of more than 24MHz over a 3,000km path. This may have been due to a short-lived ionospheric enhancement caused by a coronal hole solar wind stream, which saw the speed increase to more than 500km per second.

Next week NOAA predicts the solar flux index will remain at 69-70. Geomagnetic conditions will likely be poor, but recovering this weekend after a predicted Kp index rise to five on the 21st or 22nd. Once the coronal hole has moved, and is out of the Earth’s strike zone, the ionosphere should settle for the rest of the week.

Meanwhile, Chris, GM3WOJ and Keith, GM4YXI are still active as VK9CZ on Cocos Keeling Island, OC-003. The best time for propagation from the UK can be checked at It’s a long way to the Indian Ocean, but a contact is achievable with the right mode and at the right time.

Don’t forget that it’s CQWW CW this weekend, which always guarantees HF activity.

VHF and up

This week seems to be a good week to try satellites if you’re not active on the microwave bands! There seems to be a majority view amongst the weather models that this will be another low pressure week. It means further periods of rain and showers, with a chance of rain scatter on the GHz bands again. This unsettled weather type with a strong jet stream over the country can lead to rapid development of lows and potentially very strong winds. Not identifiable beyond a day or two, but well worth checking the daily forecasts, particularly the wind speeds.

Of course, the opposite side of the coin is high pressure, and it looks to be completely off the playlist during the coming week, which takes tropo off the agenda.

Moon declination is negative again this week, reaching minimum on Friday. Moon windows and maximum Moon elevation will fall accordingly. The Moon reached perigee yesterday, its closest approach to the Earth of the lunar month at 366,709km, so losses are low but will increase throughout the week.

The Sun and Moon are very close on Tuesday and generally, 144MHz sky temperature will also be high, reaching a peak of over 3,000 Kelvin on Thursday.

There is one small meteor shower on Thursday, the November Orionids, but nothing to get excited about because they have a zenithal hourly rate of just three.

Category: GB2RS Propagation News