Friday, 30 April 2010

HF Propagation report, May 2010

Solar conditions have not been very good in the last month. In fact we had a run of about 12 days without a single sunspot. With the solar flux hovering around 74 it was like a return to the minimum once again.

Solar flare activity has been low, but even a small change in the Interplanetary Magnetic Field (Bz) swinging south was enough to cause the HF bands to misbehave.

This was characterised during the International Marconi Day event on 26 April. The morning was not too bad with DX from the Caribbean and VK being workable on 20m in the mid morning. By afternoon is was EU only.

May 1 should see the start of the Sporadic E season. This is characterised by very strong signals in the 14-50MHz bands, with very occasional openings on 2m.

Look for very strong signals on 10m and 6m, which will suffer from heavy QSB. As the Es clouds move the countries you are able to work will change.

Peak times for Es are mid morning and mid to late afternoon, although look in the evening too.

Daytime MUFs are likely to be lower than those of winter. Older books suggest this is due to the ionosphere heating up with resultant lower ion densities. But other theories suggest that this is due to a change in ionospheric chemistry between winter and summer.

The so-called “Seasonal Anomaly” is now thought to be due to a large summer electron loss rate caused by an increase in the molecular/atomic composition of the ionosphere and the reaction rates being temperature sensitive.

It is not all bad news though. Night-time MUFs may be higher in summer than those in winter. Note that DX on the low bands, if possible, is unlikely to occur until around midnight or the early hours due to the late sunset.

So let's look at each band and what you can expect.

On 160m (1.8MHz or Top Band), high levels of static and solar absorption mean that the band will not really support sky-wave contacts during the day. During darkness, short-skip openings may occur, but DX may be a rarity. Occasional openings can occur during the hours of darkness, especially around local midnight/early hours.

80m (3.5MHz) will generally follow the characteristics of Top Band with high levels of static, but will also provide good openings out to around 250 miles during the day. Absorption will grow to a maximum at midday for inter-G contacts. DX capabilities will be poor to fair during the hours of darkness.

40m (7MHz) will suffer from high static caused by high numbers of thunderstorms. Nevertheless, night-time openings should be reliable from sunset to sunrise. Local daytime openings will be possible on the whole. Night-time skip distances are likely to be between 500 and 2,300 miles.

20m (14MHz) is still likely to be the best DX band between sunrise and sunset, although the band will be noisier than the winter period and not as reliable for long-haul contacts. The higher MUFs at night mean that 20m may remain open during the evening to DX. Short skip may also be possible due to summer sporadic-E.

17m/15m (18MHz/21MHz) should provide a fair number of DX openings during daylight hours, especially to the southern hemisphere. Once again, 15m may struggle to open at times. Both bands are likely to close after sunset. Sporadic-E will provide good short-skip openings, predominantly in the May-June period.

12m/10m (24MHz/28MHz) are likely to be disappointing bands apart from Sporadic-E openings that will provide regular openings out to around 1,300 miles. Multi-hop sporadic-E openings are possible, providing relatively good, but short-lived paths to DX beyond this range. A typical multi-hop opening might provide brief contacts with the Middle East or USA, although they would be very hard to predict. Propagation via the F layer is unlikely to occur reliably until Autumn.

You can find HF short-path propagation prediction charts from the UK at:

http://www.infotechcomms.net/propcharts/

You can also listen to Steve G0KYA's monthly HF propagation podcast on iTunes or at http://www.g0kya.blogspot.com/

Steve G0KYA
RSGB Propagation Studies Committee

UK HF propagation charts, May 2010

My HF Propagation maps for May 2010 have now been published. Please note that these don't predict Sporadic-E conditions, which should start around the 1st May. These will give short skip on bands from 14-50MHz, wtih occasional openings on 2m too.

If you monitor 28 or 50MHz you'll hear stations from around southern Europe and into Scandinavia. Signals will be strong, but with heavy QSB. They may be fleeting as the Es clouds move. Peak times will be mid morning and late afternoon, but could occur any time, including evening.

See www.infotechcomms.co.uk/propcharts

Thursday, 8 April 2010

HF Propagation Podcast - April 2010


Few sunspots at the moment, but lots of solar flare activity - boo! Find out more and also hear about the origins of Sporadic E in this month's Podcast. You can listen by clicking on the headline or search for G0KYA on iTunes.

Wednesday, 7 April 2010

HF Propagation report - April 2010

As the new cycle progresses we are starting to see more solar flare activity which is bringing aurora with it.

Over the past month we had a solar flux low of 76 and a high of 92 (on 13th March). But we've also had some serious solar flares. We had a geomagnetic A index low of 1 on two occasions and a high of 28 in the first week of April.

In fact, the A index was still climbing as I wrote this and Auroral conditions were being recorded on 6m and 2m

We are still in the equinox period as far as HF propagation goes. These tend to be the best months for working North-South paths, such as UK to South Africa.

So let's look at each band and what you can expect.

On 160m (1.8MHz or Top Band), look for short-skip and DX openings at night. Little daylight skip will be possible due to absorption, but openings out to 1,300 miles and occasionally further afield can be expected at night with conditions peaking around midnight and again at sunrise (greyline).

80m (3.5MHz) will generally follow the characteristics of Top Band at night, but will also provide good openings out to around 250-300 miles during the day. These will lengthen to around 500-2,300 miles at night with fairly good DX opportunities at times.

40m (7MHz) Forty metres should open to DX in an easterly direction at sunset. Openings to the west should be possible after midnight and should peak just before sunrise. Contacts should be possible during the day, although lower critical frequencies may mean that it is difficult to work other UK stations while perfectly possible to talk to European stations. If the flux rises then 40m may open up to NVIS contacts around the UK, but 80m will be better.

20m (14MHz) is likely to be the best DX band between sunrise and sunset. The bands may occasionally open after dark, perhaps to the southern hemisphere. Good openings will be possible during daylight hours out to around 2,300 miles.

17m/15m (18MHz/21MHz) should provide fairly good DX openings during daylight hours, especially to Africa and South America, with 17m being open more often than 15m. If we get more sunspots 15m will become a great DX band, as it did at times in February. Both bands are likely to close after sunset.

12m/10m (24MHz/28MHz) These could be disappointing bands if the solar flux remains low. If the solar flux heads towards the high 80s/90s then openings will occur on both bands, although 24MHz will open first. If it breaks the 100 mark then expect to see some good DX openings on 10m. Expect to see Sporadic E start up at the end of the month, but more of that in May.

You can find HF short-path propagation prediction charts from the UK at:

http://www.infotechcomms.net/propcharts/

You can also listen to Steve G0KYA's monthly HF propagation podcast on iTunes or at http://www.g0kya.blogspot.com/

Steve G0KYA
RSGB Propagation Studies Committee

Friday, 2 April 2010

Propagation charts for April 2010


I have just updated the propagation charts for April 2010 from the UK. The solar flux is actually quite low now and we are not seeing the rapid rise that you would expect at the beginning of the cycle. However, DX is out there, especially on North South paths. Expect to see Sporadic E starting up at the end of the month. Last year it was like a switch being thrown on 1 May.

We have Marine Radio Day on 10th April and International Marconi Day on 24 April. I have also done prop charts for the latter.

See http://www.infotechcomms.net/propcharts/