Wednesday, 29 September 2010

Propagation talk at Newark Hamfest, Oct 2010


I will be giving a talk on HF propagation and prediction programs at the Newark Hamfest on Friday 1st October. I've made the presentation available as PDF file so that anyone who attends can download it. It may not make as much sense as it will with my commentary, but there is some useful info there. It is about 7Mb.

Click to download the presentation
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Friday, 17 September 2010

History of ships' radio room clocks


Remember when all ships had real radio operators? If you do you'll know that the ops had to maintain "silent periods" when they wouldn't transmit, instead listening for distress calls on 500kHz and 2182kHz. For this they had a special radio room clock with sectors marked on it.

After the loss of the Titanic, the radio frequency of 500 kHz became an international calling and distress frequency for Morse code maritime communication. For most of its history, the international distress frequency was referred to by its equivalent wavelength, 600 meters, or, using the earlier frequency unit name, 500 kilocycles [per second] or 500 kc.

2182kHz was added later and transmissions on 2182 kHz commonly use single-sideband modulation (SSB) (upper sideband only). However, amplitude modulation (AM) was often used in some parts of the world.

Maritime coastal stations used to maintain 24 hour watches on these frequencies, staffed by highly-skilled radio operators.

As a reminder, a ship's radio room clock would have the 500kHz silence periods marked by shading the sectors between h+15 to h+18 and h+45 to h+48 in RED. Similar sectors between h+00 to H+03 and h+30 to h+33 were marked in GREEN, which is the corresponding silence period for 2182 kHz.

Anyone breaking the rules would soon hear "QRT SP" in Morse Code, meaning "STOP SENDING - SILENT PERIOD!"

I've always wanted to have one of these clocks for my own shack, but couldn't find one. So … I decided to make one. I spent two days with a graphics program recreating a radio room clock from the Winthrop Clock Company of Boston, Ma., USA. It wasn't easy, but I then took the finished result, printed it and pulled apart a quartz clock that I bought for the job and installed it - what a lot of work!

The end result is shown in the photograph above and creates quite a lot of attention in my shack. It also keeps time really well too!

There is even The Radio Maritime Day each April where you have to obey the silent periods, so it comes in useful

Anyway, after all that work it seemed a shame to waste the artwork. I then found that I could upload it to a company called CafePress, letting people buy their own clock. While I was there I also designed some T-shirts, mugs, mouse mats and other goodies.

These products, including a reproduction radio room clock, let you relive those bygone, halcyon days when "sparks" ruled the maritime airwaves. So your shack can now look like a ship's radio room!

If you are in the UK go to http://www.cafepress.co.uk/theradioroom or if elsewhere http://www.cafepress.com/theradioroom – you can select the currency you wish to pay with.

I have one of the new Cafe Press clocks - it is about 10 inches in diameter and very striking. It is quartz powered so keeps good time and the tick isn't too loud either. Looks very nice on the wall and not too expensive either.

But remember QRT SP!

Friday, 10 September 2010

Podcast: HF Propagation Report, September 2010


Report for September 2010 with a look at how solar cycle 24 still isn't going too well and why HF conditions will now start to improve in September and October. Just click on the Podcast headline above or search for G0KYA on iTunes.

Friday, 3 September 2010

HF Propagation, September 2010


Note: You can find Steve's HF short-path propagation prediction charts from the UK at:

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

Solar conditions still continue to be fairly poor. As I write this on 3 September there are sunspots, but the flux is stubbornly in the mid to high 70s. There have been auroral conditions over the past few days and we can expect to see more unsettled conditions as the cycle progresses.

Having said that, conditions are improving due to seasonal variations. We are heading away from the summer solstice and towards the equinox. The ionosphere is cooling down and its chemistry is changing. Traditionally late September and October are good times and we can expect to see increasing DX being worked.

In some respects this has already started to appear. There have been some good 20m openings from the UK to the West Coast of the USA and Alaska, plus openings to the Far East.

Given the lowish solar flux I think we will continue to see 20m (14MHz) and 17m (18MHz) as the “money bands”, but don't write off 15m (21MHz) which will open to DX, but perhaps not as often as the lower bands.

Late September will be the acid test – and with flux levels in the 70s we are unlikely to see many (any?) trans-Atlantic openings on 10m. Sorry - I would love to be proved wrong!

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

The equinox periods provide longer daytime periods than winter, but logically, shorter night-time periods too. These tend to be the best months for working North-South paths, such as UK to South Africa and South America.

On 160m (1.8MHz or Top Band), look for short-skip and DX openings at night. Again, no daylight skip is 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 miles during the day. These will lengthen to around 500-2,300 miles at night with fairly good DX opportunities at times. At this point in the cycle 80m should still provide good DX around midnight as absorption is still quite low.

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.

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. Once again, 15m may struggle to open during times of low solar flux, but could provide good openings if it rises above about 90-100. Both bands are likely to close after sunset, at least later in the month..

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, especially in late 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 HF propagation podcast on iTunes or at http://www.g0kya.blogspot.com/

Steve G0KYA
RSGB Propagation Studies Committee