Friday, 7 October 2016

GB2RS Propagation Presentation

On Sunday 9th October I'm giving a talk at the RSGB Convention on how we prepare the weekly RSGB GB2RS Propagation report.

This looks at HF, VHF, moonbounce, aurora, rain scatter and much more.

To save people hurriedly scribbling down all the URLs in the presentation I have turned it into a PDF for download with all the URLs hyperlinked.

I'm not sure if this is of too much use if you haven't seen the presentation, but it does show all the resources that are used each week.

You can download the PDF at:

Wednesday, 28 September 2016

Coronal holes causing chaos on HF bands

Coronal holes appear as dark patches when
viewed in extreme UV light via the SDO spacecraft.
The past few months have seen very poor HF conditions with the higher bands often closed and maximum usable frequencies below 14MHz during daylight hours. This has been coupled with high K/A indices and aurora.

But what has been the cause?

HF conditions are generally worse in the summer months, with lower ionisation levels overall during daylight hours in the northern hemisphere.

This is believed to be due to a change in the chemical composition of the F layers of the ionosphere, with a predominance of molecular rather than atomic oxygen and nitrogen [1]. That is, atoms that are paired up have stronger bonds, which means it is harder for ionising radiation to liberate electrons. The actual process is quite complex and depends upon the ratios of [O]/[O2] and [O]/[N2]. The reaction is also temperature sensitive.

But over the past few months we had had an added problem – coronal holes (CHs) and coronal mass ejections (CMEs) from the sun.

A CH is an area on the sun where the corona is darker, colder, and has lower-density plasma than average. The magnetic field around a CH is also different – instead of returning to the surface, the magnetic field lines remain open and stretch out into space.

This can allow the charged solar wind to escape at high speeds, often up to 600-700 kilometres a second.

When a CH is positioned near the centre of the Earth-facing solar disk, especially when the “frozen in” magnetic field of the escaping plasma (Bz) points south, it can more easily couple with the earth's magnetic field.

The hot gasses can then flow to Earth as a solar wind high-speed stream (HSS), causing geomagnetic disturbances, including enhanced auroral activity and absorption at high latitudes. We can detect this geomagnetic storm as the Kp index rises to four or more.

Other effects can include a lowering of the critical frequency as the F layers are depleted causing the upper HF bands to close down. Higher noise levels may also be evident.

We can “see” CHs on the sun thanks to spacecraft. When viewed in the extreme ultraviolet light or X-ray spectrum they appear black due to their lower energy levels. The Solar Dynamics Observatory (SDO) has an X-ray imager called the Atmospheric Imaging Assembly (AIA) and its imagery can be found at – look for “AIA 211b W/ Coronal Holes”.

CHs can also be long lasting, their effects often being observed on several solar rotations (27 days) [2].

But the CH effects have also been augmented by CMEs. These are often linked to a solar flare and occur when the magnetic field within a sunspot breaks down allowing millions of tonnes of plasma to be ejected. This has similar effects to a CH as the plasma hits the earth, especially if the CME's magnetic field (Bz) is pointing south.

But why the sudden increase in CHs and CMEs recently?

Observation has shown that the sun is more unsettled after a peak in the sunspot cycle, with more frequent CMEs around solar maximum and CHs on the declining phase. The past few months have seen the decline of Cycle 24 – the least active in our lifetimes

In 2013 NASA spotted a CH that was at least 400,000 miles across – more than 50 Earths side by side [2]. And in March this year scientists saw one of the largest polar CH's they had observed in decades. It covered an estimated six- to eight-percent of the total solar surface [3].

CHs were first seen in images taken by astronauts on board NASA's Skylab space station in 1973 and 1974 [4]. So our data only go back two or three sunspot cycles, and we haven't got a lot to go on.

We know CHs can be long-lasting and we think they move closer and closer to the sun's poles near solar maximum.

But the best guess is that we will be stuck with CHs, CMEs and their effects for at least a few more years yet as we head towards sunspot minimum around 2020.


1. “The Solar-terrestrial Environment”, J.K.Hargreaves.
4. “The High-Latitude Ionosphere and it effects on Radio Propagation”, R.D.Hunsucker and J.K.Hargreaves.

Originally published in RSGB's RadCom magazine

Tuesday, 2 August 2016

More great tins for QRP radio projects

Click to enlarge
Regular readers will know I've built a couple of QRP HF radios into mint tins. The first was a 20m Rockmite ][ built into a Stewarts' tin with a Spitfire on the front. 

The second was a 40m Foxx-3 built into a Stewarts' train tin.

This all came out of a desire to build something in an Altoids tin or similar having been inspired by the fantastic radios built by Colin M1BUU.

He showed me a Steve Weber-designed ATS (Appalachian Trail Special) in an Altoids tin at a Rishworth QRP convention and the workmanship was fantastic.

Anyway, both my radios work, but at around 1W or less QSOs can be quite hard work – must dig them out again soon and have another play.

But this has set me on the trail for more and better mint tins and I found a couple of crackers recently.

The first depicts the White Star Line and was bought for £3.50 at the Bressingham Steam Museum in Norfolk. They had other designs and it appears to be made by a company called Half Moon Bay in Bath. They are a wholesaler, but do have links to an online stockist – Kitsch-a-go-go – which has lots of different tins.

The second tin was found at the British Motor Heritage Museum at Gaydon and depicts an MGA sports car. It is also a little bigger than an Altoids tin and cost £4.

This was made by a company called Red Hot Lemon. It has a minimum order of £100 unfortunately, but you could always club together with someone else to buy some.

Now, all I need is another kit to build. What I'd really like is a 3W 40m and/or 20m radio transceiver, preferably synthesised so that you move around in frequency that would fit in a standard Altoids tin. So basically, a Steve Weber ATS or MTR – shame they are not being made in kit form. I have a three-band MTR v2 which is my pride and joy.

If you know of any other suitable kits please let me know by commenting below.

Thursday, 28 July 2016

Repairing a cross-needle SWR meter

The SWR meter - working 100% again.
I've owned an AEA ET-1 antenna tuning unit for the last 20+ years. In that time I've had to replace the inductor switch as it burned out and also replace the meter.

Luckily, it uses exactly the same meter as MFJ ATUs so I was able to buy a replacement from them. I also resprayed the case at some point.

But recently the meter started playing up – it would only indicate 20W maximum forward power instead of 100W.

It was more of a problem on the less than 30W setting as I often use QRP radios and need to know if I am putting out 2W or 5W.

You could ask “why not just bin it?”, but that's not in my DNA!

Anyway, after asking for advice on the CDXC forum and looking at the schematic I decided that it could only really be down to a failed capacitor, resistor or diode. Given that semiconductors would be the first suspect I ordered two new 1N270 diodes from a UK supplier on Ebay for £3.98.

When they arrived I unsoldered the old ones, and checked them – one measured 1K Ohm resistance in both directions – not good and definitely not diode-like behaviour.

I soldered in the new diodes and bingo the meter is back to normal again. I've since ordered some 10 more 1N270s from China for just £1.12 inc. postage. These will do as spares.

I'm writing this as it might be useful to owners of cross-needle SWR meters in future. If you start to get low readings it may be the diodes. If you get no reading at all it is probably the meter.

Friday, 22 July 2016

Elecraft K1 QRP radio finally finished

My Elecraft K1 (click to enlarge)

You could say that this project has been a long time in the making. The kit for this Elecraft two-band (40m/20m) K1 5W CW radio was actually a Christmas present back in 2004.

Heck, I still have the invoice for $329 plus the £44.97 import duty, making it about £230.97 at the exchange rate of the day (nearly £300 at today's rates).

When I first got the kit I had a couple of reads of the instruction manual, went “wooah” and put it in the loft. It even moved house with me eight years ago.

Anyway, a conversation with Colin M1BUU (a more enthusiastic QRP builder and SOTA operator you couldn't wish to meet) at the 2014 G-QRP Convention convinced me that I really should put it together.

In the intervening 10 years I have built a lot of other kits, including a Hunter SDR, Rockmites, MKARS 80 and a Steve Weber MTR, so I had picked up a lot of construction skills.

Last Christmas I actually started the build and, while not difficult, it was time consuming. Fast forward to July and I thought it was about time I finished it.

The build wasn't too bad, but I had a few problems, such as the wiring on the multi-turn pot for the VFO control – I thought the numbers on the side of the pot represented the numbers in the manual. They didn't.

I also managed to loose a couple of components down the back of the bench, which were subsequently found, and also couldn't find the insulating spacer for the power transistor – this I managed to improvise with insulating tape and fibre washers.

The final c*ck-up was missing out two capacitors, which meant the receiver didn't work at all. I'm glad I eventually managed to debug it without any help.

In all, I think I spent about 22-25 hours putting it together, but the end result is worth it.

The Elecraft K1 has a fantastic little receiver and a built in keyer and puts out around 7W if pushed. I have had a couple of QSOs with it so far and it is a very useable QRP radio.

I can thoroughly recommend it as a QRP project, although Elecraft have now moved on quite a way with the KX2 and KX3 - but then my K1 kit is 12 years old!

Tuesday, 19 July 2016

Operating QRP from Beeston Bump (TG14) in North Norfolk

Update: YouTube video now available

Jim G3YLA and I operated HF and VHF QRP from the top of Beeston Bump in Norfolk as planned today.

It turned out to be the hottest day of the year, so not exactly ideal. Nevertheless, after parking up and walking to the top we were met by a fantastic 360 degree view.

I quickly set up by 40m inverted L end fed half wave (EFHW) on a 10m fishing pole, bungeed to a bench and fed it with my homebrew EFHW matching unit, while Jim tried some CW on 2m from a little beam. He didn't get anywhere with that so switched to FM and had a quick chat with some locals on 145.275MHz.

Once the HF antenna was erected I handed Jim the coax and he set to on 40m CW and quickly worked a station in Germany using 2.5W from his Yaesu FT-817.

Jim G3YLA working Germany on 40m CW.
I meanwhile tried to see what I could work on 2m FM and could raise the GB3FR repeater across the water in Spilsby, Lincolnshire, but there was no one on it. I switched to GB3NB in Norfolk and worked John G8VPE.

I then took over on HF, but 40m was hard work and 20m was not much better. I eventually went back to 40m CW using my 2.5W Steve Weber-designed Mountain Topper Radio (MTR) and raised fellow G-QRP club member Peter G3XJS near Wrotham, Kent who was using 5W to a doublet. I was very pleased to make the contact as that was the first time the MTR has been used in the field.

Looking at the Chilton Digisonde data I think this was via Sporadic E (Es) on 40m as the F2 critical frequency was only about 5MHz - we don't normally associate Es with 40m, but you could see the Es on the plot.

Jim G3YLA then took over again using his FT-817 and had a long CW QSO on 40m with a station in the Netherlands. 

The information board for the Y station.
There were a lot of walkers on the hill and we were able to explain what we were doing - it was quite apt as this was the location for the Beeston Hill Y Station, a secret listening post during World War Two. The chain of Y stations were on the front line, feeding Enigma intercepts to the War Office’s Bletchley Park.

There is an information board all about the Y station and the concrete foundations are still there.

Propagation was iffy at best and the heat was getting to us, so we decided to take the station down and head for the nearest pub for fish and chips and cold refreshments.

My home-made EFHW matcher and SWR
All in a great day and we both agreed we'll go back, perhaps in late September when propagation is better and the temperature is a bit more reasonable.

I also shot some video and I'll try and edit that over the next few days.
My three-band (40, 30 and 20m) Mountain Topper Radio.
3W CW on 40m raised Peter G3XJS in Kent.


I thought I would do a Reverse Beacon Network (RBN) check tonight.

I was pleasantly surprised to see I was picked up all over the place, including the US, from the top of the bump.

Jim G3YLA wasn't for some reason - not sure why as his CW is waaaay better than mine. Perhaps it was because he responded to CQs and didn't call CQ himself.

Reverse Beacon Network captures from the day -
chuffed I was picked up in the US (just) with 2.5W to an EFHW for 40m (click to enlarge).
Update: YouTube video now available

Saturday, 16 July 2016

G0KYA to operate a "BOTA" station - "Bumps on the Air"

Beeston Hill near Sheringham in North Norfolk.
Image Wikimedia/Stavros1
I plan to operate QRP from Beeston Hill in North Norfolk on Tuesday 19th July as part of a new "BOTA" activation.

BOTA stands for "Bumps on the Air" a wholly-fictitious new organisation for radio amateurs who don't have access to real summits and mountains.

Beeston Hill (known locally as 'Beeston Bump') is not the highest point in Norfolk, but at 63m (207ft) above mean sea level it offers a good view of the coast and excellent HF take off.

I wanted to have some outdoor local QRP SOTA fun, but Norfolk is a little short of suitable summits (well, none actually) and Beeston Bump will have to do.

The highest point in Norfolk is nearby Beacon Hill at 103m (338ft), but I don't want to overstretch myself! Anyway, the view is better at Beeston and there are more ice cream shops nearby.

I've been meaning to do this for years!

Beeston Hill Y station circa 1940.
Image; Wikipedia.
I plan to operate 40m and 20m QRP CW using one or more of a variety of commercial and kit-built radios, including a Yaesu FT-817, Elecraft K1, Mountain Topper Radio (MTR) by Steve Weber KD1JV and a 1W Rockmite. Antennas will be end-fed half wave (EFHW) dipoles.

Beeston Bump is no stranger to Morse code. Beeston Hill Y Station was a secret listening post located on the summit during World War Two. The chain of Y stations were on the front line, feeding Enigma intercepts to the War Office’s Bletchley Park.

There are no awards for working me on Beeston Bump, no certificates and no special QSL cards - just my normal one. And just the fun of working CW at about 16-20 wpm around the usual QRP watering holes on 20 and 40m. I hope to be there from about 10:30am.

Jim G3YLA, a fellow QRP enthusiast, might be with me too.

(With apologies to the excellent Summits on the Air (SOTA) organisation!)