Wednesday, 29 March 2017

You never know who you might hear on HF!

Colonel Doug Wheelock, KF5BOC
I was tuning around HF today and heard an American accent on 14.275MHz. This was odd as conditions had been really bad because of a geomagnetic storm, complete with a K index of six.

I didn't think there would be much propagation to the US.

Listening carefully it turned out to be Keith RA/WD9GET in Star City, Russia. Keith is a flight surgeon with NASA and was operating the amateur radio station at the cosmonaut/astronaut training centre in Russia.

Before I had a chance to call him he said he was taking a break. That was a shame, but I left the rig running on 14.275.

Ten minutes later RA/KF5BOC came up on the frequency and was calling, so I replied. He was a good 59 on my 40-10m EFHW antenna at about 25feet.

It turned out to be Colonel Doug Wheelock KF5BOC, the International Space Station commander, who is in Russia at the Gagarin Space Centre to help with training. Blow me down!

So Doug and I were able to have a quick chat and when we finished the pile-up started - big time.

Just shows you never know what you going to come across on HF.

Friday, 27 January 2017

A shortened multi-band End-Fed Half Wave (EFHW) antenna for 80-10m

The 80-10m EFHW
This is a shortened multiband antenna, about 23m long, for 80m-10m that offers low SWR (1.3:1) on 80m and 40m, and below 3:1 on 20, 15 and 10m. The antenna has almost 300kHz bandwidth on 80m between 3:1 SWR points. But performance is down about 8-12db on a dipole on 80m.

This design came from attempts to find an 80m antenna that could fit into a small space. This was because Norfolk Amateur Radio Club likes to take part in the 80m Club Championship (we won in 2016), but many members don't have enough space for a full size (132ft) dipole or the 100-102 feet needed for a G5RV or W5GI antenna.

This antenna lets you get on to 80m in a horizontal distance of about 12m (40ft) when used as an inverted sloper with the apex at 8m, although you'll be down a couple of S points on a dipole. But if the other station is 59+20dB, you'll be about 59 +5 or 10db, so all is not lost!

I take little credit for this as it was outlined in PD7MAA's and IK0IXI's blogs after extensive work on the antenna in the Netherlands. However, there was little on their blogs in terms of its performance or SWR characteristics. Hence this write-up.


Download the 80-10m EFHW antenna guide

Update 29/1/17:
I've updated the guide to look at replacing the coil with a 7MHz trap and also putting the antenna up as an inverted V.  The trap and about 14.2m of insulated wire would improve the 80m performance a little, if you have the space, but possibly at the cost of the 14MHz performance. Surprisingly the MMANA-GAL model suggests the inverted V would be worse for 80m NVIS communication.

Update 09/02/17
I thought I would bite the bullet and took the wire and loading coil off and replaced it with about 130ft of insulated wire. This needs some final tuning, but gives a low SWR across 80 and 40m, and SWRs below 3:1 across the higher bands. The last 20-25 feet had to run along a wooden fence. Performance on 80m was equal to or down 1-2 S pts on the W5GI. Performance on 40m was down quite a bit, perhaps 2-3 S pts.

It appeared to be directional compared with the W5GI (which was at right angles). Equal performance on 20m to Tunisia.

So the performance on 80m was marginally better than the shortened version, but the 40m performance was worse. This was confirmed with WPSR tests. The performance on 20m was roughly similar. The bands higher than 20m were mostly closed during the test.

I think the compromise position of the 132ft wire didn't help the antenna's performance and I think that overall, the 66ft and loading coil version was better on 40m an higher.. If you could get the whole wire in the clear you might better results.

Monday, 9 January 2017

HF and solar conditions continue to decline

I've now updated my hourly HF propagation charts for the UK for the next three months.

The charts, with real time solar information, can be found at http://www.infotechcomms.net/propcharts/
You can definitely see the effects of the current poor solar conditions. As the charts are produced by VOACAP it is suggested we use the smoothed sunspot number (SSN) for the calculations.

In January 2016 the SSN was 44.8, but this month it is just 29.2. In fact, the actual daily sunspot number is even lower than this at around zero to 11 with a solar flux index in the low 70s.

Given that at sunspot minimum we wouldn't expect the solar flux index to drop below 66 you can see that we are very close to the kind of conditions we can expect over the next few years.

NASA says the current sunspot cycle is the smallest since cycle 14, which had a maximum smoothed sunspot number of 107.2 in February of 1906.

The current prediction for sunspot cycle 24 (this one) gives a smoothed sunspot number maximum of about 101 in late 2013.

The next sunspot minimum is currently predicted to occur around 2019-2020.

The solar maximum for cycle 25 is predicted to be around 2025, possibly with a monthly smoothed maximum sunspot number of around 60-65. If true, this is almost down to Dalton Minimum levels.

What we are seeing is that the ionosphere is currently struggling to regularly open up to DX at frequencies much higher than about 18MHz. Around the UK we are even finding 40m (7MHz) closing to inter-G contacts by early afternoon, if it opens at all.

This means that 80m (3.5MHz) and 60m (5MHz) are coming into their own, although both are struggling with inter-G contacts by late afternoon.

A succession of coronal holes and their associated high-speed solar wind streams are also causing disruption to the ionosphere. While these are typical of this point in the sunspot cycle they are generally not helping DX at all.

This week's high K indices have been caused by such a hole, although the solar wind has mostly had a north-facing Bz field, which is less likely to couple with the Earth's magnetic field, and we have't seen the very high K indices that indicate severe auroral conditions.

Lastly, readers might be interested in a new HF propagation tool based on the ITU's ITURHFPROP software and developed by Gwyn G4FKH. The URL is http://www.predtest.uk

The 'Area Coverage' predictions have been available for some time, but a new Point-to-Point prediction tool is now available. Clicking on the link starts the process, when the form is filled out a series of plots are available depicting propagation between the required Tx. and Rx. sites.

New features include various colour schemes for the plots allowing users with colour preferences to make the best viewing choice for themselves.

Steve G0KYA

Monday, 2 January 2017

Some Christmas QRP HF operating

Elecraft K1 on 40m QRP frequency.
The period from Christmas to the New Year is traditionally the time for the GQRP “ Winter Sports”.

I don't take this too seriously as there are plenty of other calls on my time, but it is an opportunity to get on the air and work a few stations with 5W CW or 10W SSB.

This year got off to a good start with a contact on 23rd December with SK6SAQ at Grimeton in Sweden – home to the Alexanderson alternator that puts out a 200kW signal on 17.2kHz.

SAQ also has a special event callsign so it was good to get operator Kjell in the log using 5W from a Yaesu FT-991 into an outside EFHW. I really must visit Grimeton one day.

I also dragged out my Bencher paddle as I was sending some awful Morse with my Kent single lever I think I was getting key bounce so will have to take a closer look. The Bencher was fine, which was good news.

After Christmas I turned to my Elecraft K1, which I finished in the summer after owning the kit for about 12 years!

This brought CW QSOs with Peter OM0WR in the Slovak Republic on 7.029MHz with 5W into my loft-mounted zig-zag dipole.

The YT160TESLA QSL card.
Then it was YT160TESLA on 20m celebrating 160 years since the birth of Nikola Tesla in Serbia. I really want their QSL card which looks great and worked them on 40m in March. As they went QRT at the end of 2016 it really was a last chance.

I have an Icom IC-7300 on test, which belongs to my local club and that brought 9A1700SBD in Dubrovnik, Croatia, although it took 25W to get through.
The view across the rooftops of Dubrovnic, Croatia.

2016 was the 1700th anniversary of St. Blaise, patron saint of Dubrovnik – if you ever get the chance to go there, do as it is absolutely beautiful.

Station LZ463PP then went in the log with 10W from the IC-7300 and a W5GI dipole on 17m SSB, so still QRP. It was celebrating 463 years of Saint Patapii.

Finally I had a nice (but weak) QSO with Ian EA7JUK in Lubrin, Spain on 20m CW using 5W from the K1 and an indoor dipole. Ian's UK call is G0WHX.

The Reverse Beacon Network proved everything was working!
Sunday 2nd January marks the QRPARCI New Year's Day Sprint, but I really didn't expect to hear anything from the US due to rotten HF conditions. If I do I'll update the blog!

So, I heard a lot more stations than I worked, but I had fun – which is what it is all about.

Wednesday, 14 December 2016

Working Santa's elves in Lapland, Christmas 2016

Every week I produce the HF propagation report for the RSGB's GB2RS news. This week I thought I would do something a little different. If you have children or grandchildren they might find it interesting. I worked them on 20m SSB on the 14th and they were LOUD! Here is the report:

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This week we have a slightly different approach to the HF propagation news. We want to help you and your family contact Santa's elves in Lapland, Finland.

The station Oscar Foxtrot Nine X-ray (OF9X) is once again on the air this Christmas from Santa Claus land in the Arctic Circle.

Twelve elves are operating OF9X (that is, “Old-Father-Nine-Christmas”) from the city of Oulu in Finland for the entire month of December

To work the elves at OF9X, the best starting point is the DX cluster or reverse beacon network to see where they are operating. They have been spotted on many bands and modes over the past week.

The HF predictions suggest seventeen or twenty metres (18MHz or 14MHz) both give a good possibility of a contact with a probability of greater than 90% during the hours of daylight. Even 15m may be possible around midday.

Forty metres (7MHz) should also give a high probability for the whole 24 hours, while 80m and 160m may also be open during the hours of darkness in the UK.

But get in quick, NOAA is predicting unsettled geomagnetic conditions from December 19th to the 23rd due to a recurrent coronal hole.

Wednesday, 30 November 2016

Quarter wave verticals for HF

The radiation pattern for a quarter wave vertical.
I had an email from a radio amateur who was struggling to work DX after putting up a very off centre fed dipole cut for 40m and fed with open wire feeder.

This is probably not the best way to go about it as the off centre feed can cause an imbalance and create RFI problems.

I suggested a better DX antenna might be a quarter wave vertical cut for the band in question and fed against a decent ground plane. But what is a decent ground plane?

Rudy Severns N6LF has done extensive research on this, but his conclusion was that you really need as many radials on the ground as possible. Up to 120 is optimal, but you will notice an improvement as you add more and more with perhaps 16-32 being the minimum for good performance.

Don't be misled by your SWR meter as a single earth stake may give you a low SWR, but what you are seeing may be the effect of ground losses.

A quarter wave vertical should have a theoretical impedance of about 35-36 Ohms, so if you have a 1:1 match you are seeing 35 Ohms, plus 15 Ohms of ground losses.

As you add more and more radials the SWR may INCREASE. This shows it is starting to get closer to the optimum 35 Ohms.

The goal is to keep on adding ground radials until the SWR stops changing. Then the vertical is working about as good as it can.

Rudy found that once you get above 32 ground radials the improvements start to get more subtle and increasingly minimal.

But how long should the radials be be? A quarter wave radial laying on the ground is detuned so a true quarter wave is no longer a resonant radial, although it is a good overall compromise.

So the golden rule is that for a given amount of wire more shorter radials are better than fewer longer ones. This helps to collect the ground currents around the base of the antenna and improves the antenna's efficiency.

If it is a multiband vertical then the compromise is to make them as long as the antenna is high. If it is a monoband antenna then perhaps a quarter wave is best, although eight "eighth wave" radials might work better than four quarter waves (if on the ground).

In tests though you will find that two resonant elevated radials fitted so that they are at 180 degrees to each other may work as well as eight or so random radials on the ground. Rudy suggests that more resonant quarter wave elevated radials may be better still, but its starts to get a bit unwieldy.

A few years ago my club used a quarter wave vertical cut for 40m and fed against two elevated quarter wave radials and it worked very well. For contacts out to Germany from the UK there was little in it compared with a horizontal half-wave dipole at about 40 feet. Closer-in contacts were louder on the half wave horizontal dipole due to the different radiation pattern, but for DX the vertical was better.

You can see this with the MMANA-GAL antenna modelling software.

We also used it on 21MHz where it was a three quarter wave vertical and ended up working India (VU).

As you can buy 10m fibreglass fishing poles for about £30 you can make an effective quarter wave vertical for very little money.

The length of the radiator will then be 300/7.1MHz = 42.25m/four = 10.56m.

If using PVC-coated wire the adjusted length will be about 10.56m x 95% = 10.03m, although start a little longer and fold or cut to get the SWR minimum.

For a 30m quarter wave vertical the sums are:

300/10.1MHz = 29.7m/four = 7.42m or about 7.054m if using PVC-coated wire.

Once optimised expect to see an SWR of about 50 Ohms/36 Ohms (the impedance of a quarter wave vertical) = 1.4:1 or 1.5:1 NOT 1:1.

Although putting a quarter wave vertical (or Hustler/Butternut) on a single earth stake will work, you are throwing away its efficiency.

Why not try building one and let me know how you get on?

Thursday, 24 November 2016

Christmas present ideas!

As Christmas is coming, I thought I would remind people that there are some great radio-related goodies for sale at CafePress.co.uk and .com.

You can choose from a number of items, including:

  • Three different types of ship's radio room clock, with silent period sectors marked
  • "Remember QRT SP" Merchant Navy Radio Officer merchandise
  • "Keep Calm and Work Some DX" merchandise
  • "Keep Calm and Work Some CW" items
  • Nikola Tesla merchandise, featuring him sitting in his Colorado Springs laboratory in 1899, surrounded by electrical arcs.

You can have the last three slogans added to T-shirts, sweatshirts, mouse mats, calendar, mugs and much more.

Just go to the Radio Room!

Or there are a number of my radio-related books that make good presents , including "Radio Propagation Explained", "Antenna Modelling", "Stealth Antennas" and "Getting Started in Amateur Radio". Use the image links on the right for more information.