Wednesday 31 August 2011

10m Slim Jim antenna

For dimensions see PDF
I can't take much credit for this. The original 2m Slim Jim was designed by Fred Judd G2BCX, who lived in Norfolk before he became SK some years ago.

This 10m one, made from 450 Ohm slotted ribbon cable from Moonraker and secured on an 8m fishing pole, was inspired by Jim Bacon G3YLA (also a fellow Norfolk ham) who brought one along to our annual “Radio by the Seaside” event.

It worked so well (beating a Rybakov vertical by about 6 S points) that I thought it needed more attention.

The result is attached - it took a lot of fiddling to optimise the length, cut out and feedpoint, but now you don't need to!

Tuesday 23 August 2011

Working T32C from the UK

Update: Presentation download now includes comparison of predictions v actual as at 9th October.

The Five Star DXers Association are off to Christmas Island (Kiritimati) T32C in late September. If you want to work T32C it will pay to do a little bit of planning. In terms of the propagation to that part of the world there are a few factors we need to take into account.

The first question is “where is it?”. Kiritimati, or Christmas Island, is a Pacific Ocean atoll in the northern Line Islands - it should not be confused with an island of the same name in the Indian Ocean (VK9/X)!

The island lies 144 miles north of the the Equator and 8,400 miles from the UK

This highlights the first propagation problem – Kiritimati lies on a beam heading of about 335 degrees from the UK which puts our signals slap bang through the auroral oval around the north pole. Conversely, the long path heading of 156 degrees (and 16,400 miles) goes through the south auroral oval.

I have written a feature on propagation to T32C from the UK, which will appear in RadCom. I am also giving a talk on the subject at the RSGB Convention in early October.

In the meantime feel free to download a copy of the presentation, complete with notes, to get a feel for how hard (or easy) it is going to be.

Download the presentation in PDF format (1.4Mb)

Thursday 11 August 2011

Podcast: HF Propagation Report, August 2011

A look at the last 30 days' solar and geomagnetic conditions and the link between sunspots and solar flares. Why you should use the smoothed sunspot number for prediction programs and how the Sporadic E season is coming to an end.

Click on the headline to listen to the programme online or if you prefer to listen to it on your iPod search for G0KYA on iTunes.

Tuesday 2 August 2011

UK propagation charts for August 2011

Well, we are moving away from the summer solstice, but we are a long way from the better autumnal HF conditions that we should start to see in mid September. The summer sporadic E season should also be diminishing too. The last month or so has been characterised by big swings in the solar flux index and pretty poor conditions, although it doesn't pay to generalise. A chance glance at 17m a week or so ago showed a station from Los Angeles, calling CQ and with very few takers. He was about the only signal on the band! These charts are based on a smoothed sunspot number of 45. The SSN is what is recommended by the originators of VOACAP and might seem a little low, but it is supposed to give better predictions. Go to the propagation charts