Monday, 22 September 2014

NI6IW, USS Midway, San Diego

I was lucky enough to visit the USS Midway aircraft carrier in San Diego, California, last week while on a work trip.

It is now a floating museum, dedicated to telling the story of how an aircraft carrier functioned, with a lot of the stories told by ex-Navy personnel who served on it.

I was even more lucky because Hal KI2HAL gave me a behind the scenes tour of the ship's amateur radio station NI6IW.

It has three Elecraft K3s that allow it to work all bands. Because of the museum's rules, all the antennas have to be the original authentic models fitted to the ship when it was in service. This means that the ham station uses a couple of navy verticals and a sloping three-wire set-up.

Hal KI2HAL
I was able to tune one of the verticals for 17m to see if I could work the UK – a distance of more than 5,000 miles. I didn't make contact, although I think I did hear G3SGE on CW working a CT station. I've not been able to track down who G3SGE is though.

The ship also has an Icom D-star set-up and makes a lot of contacts that way.

The ship is active on the Museum Ships weekend "on the air" days so you might be lucky to hear it.

The antennas
In all, the ship is fascinating – you can hear from a retired Navy pilot exactly how you land and take off on an aircraft carrier. Hairy stuff.

My thanks to Hal for showing me around. Just click on an image above to see a bigger one.

Thursday, 11 September 2014

Signs of 10m opening up again for Autumn

In September, 10m propagation from the UK generally favours
north-south paths.
Nice to see 10m starting to open up again this Autumn. With the solar flux index (SFI) at around 160, I was testing a new antenna yesterday and heard 3B9FR (Robert) on Rodriquez Island in the Indian Ocean.

I bagged him first call on CW and thought it might be an opportunity to see what else was on. Two minutes later I had the ARRL centenary station W1AW/5 in the log from Texas on 10m.

I also heard low-power 10m beacons from Florida, Alabama and New Hampshire. Luckily, I heard all this before the X class solar flare hit us at 17:45UTC. The associated coronal mass ejection (CME) will no doubt cause us problems in the next 24-48 hours.

It is a little early in the season for the Northern USA on 10 metres to be reliable (see my prediction charts), but it bodes well.

In view of the date today, it did remind me of that fateful “9/11” back in 2001. On that day the SFI was 250 and I was working in my shack in the UK listening to the KQ2H repeater in New York on 29.620MHz, I heard the whole scenario played out.

From the first conversations suggesting that a Cessna had crashed into the WTC, to the full horror some time later. Eventually all communications ceased – I only found out later than the repeater was actually on top of the WTC itself, which explains why it went off the air.

Nowadays KQ2H is still on 29.620MHz, but is located in the Catskill mountains of up state New York. When conditions are right it is very loud indeed and a great indicator of good 10m propagation into the USA. I expect we will be hearing more of KQ2H in the UK over the next month or so.

This is a good time to prepare for worldwide 10m openings in the coming months. Don't miss them!

Tuesday, 2 September 2014

Steve Weber KD1JV's MTR three-band QRP radio


I finally finished my new HF QRP toy and it works a treat. I put my name down for the latest Mountain Topper Radio (MTR) design from Steve Weber KD1JV a few months back. Steve only releases a limited number of his designs each time and I was lucky enough to get one.

The finished three-bad MTR QRP rig.
Steve's radios are legendary and include the ATS-3/ATS-4 and derivatives.

The latest MTR is a three-band 2.5-3W QRP transceiver that can be built for 40m, 30m and 20/17m. It can even be persuaded to go onto 80m apparently. It is very advanced with a built-in keyer, memory, attenuator, single character digital readout, Morse annunciation and much more.

The best thing is it is tiny – about the size of a pack of playing cards.

I attended the G-QRPconvention last October and was inspired by some of the tiny QRP radios people had there, especially Colin M1BUU who had some rigs that were real works of art.

I held fire on building it for a couple of months to see if there were any changes to the instructions. As it was, Steve had to send out another chip as the original keying algorithm wasn't quite right.

So, with new chip in one hand and a very fine-tipped temperature-controlled soldering iron in the other I tentatively set about the build.

First off, this isn't one for beginners. It is about 90% SMD and the parts are tiny. Having learned my lesson the hard way I used a large baking tray to work on in an effort to stop parts flying off, never to be seen again. As it was I did loose one part for a few hours but eventually found it in the carpet. With components just 1-2mm in length this kit is not to be sneezed at – or over!

I took my time, spreading the build over five three-hour sessions. Apart from putting three capacitors in the wrong place (which I was able to retrieve) it went together quite well. On power up it received first time and I was able to go through the set-up routines with no bother, using a PC with PSK31 software to set up the oscillator on 10MHz as instructed.

But then it wouldn't transmit any RF. I eventually tracked it down to a poor joint on the L18 output toroid – I hadn't got all the enamel off one of the leads.

Bear in mind that this board is only 8.5cm wide.
I managed to get 3W out on 40m and 30m with a 10.1V pack of eight Ni-Mh batteries. On 20m I got about 2W. After glueing the cores to the board to make the whole structure more rigid I found that other people have said you can probably get another Watt out on 20m by removing a turn from the two 20m toroids.

Adopting the “if it ain't broke don't fix it” methodology I'm happy with 2W!

Incidentally, when I took the photograph of the board I noticed that there was a stray filament of wire laying on a chip. This must have come from when I was doing the final wiring. I've now removed it, but it goes to show how a digital camera can be a Godsend with SMD construction.

So does it work? Oh yes!

My first outing on 40m at home brought back Gunner OZ6NF in Copenhagen who gave me a 559. Next up was Pascal F5UQE in Lille who gave me 589.

I think this is an excellent fun radio and ideal for backpacking – if only we had some mountains around. The nearest big hill is 150 miles away from here!

So how do you get your hands on a Steve Weber designed radio? First you have to join the “AT_Sprint” Yahoo Group. That's where Steve announces that he is going to make a quantity of kits. Secondly, when he announces that this is going to happen you send him an email. If you are then lucky you will be selected and have to pay via PayPal. Good luck – the interest level is very high.

Overall, it is a fantastic design and well worth making.


73 de Steve G0KYA

Update 3/9/14; Tried it out on 20m today and worked Switzerland, Spain and Belarus. Went back to 40m and worked Moscow. Sensitivity is pretty good - not quite an Icom 756 Pro3, but look how big it is! Lots of fun. 

Wednesday, 20 August 2014

HF and Medium Wave 65-ft Inverted L

The SRC X65 with its original box, now long gone.
I've been using a 65ft inverted L with a 9:1 unun for some time. It was originally made by the Snowdonia Radio Company (SRC), but I have had to rebox it as the unun box cracked and filled with water.

With a new box and stainless steel bolts and fittings, the antenna works well from 20m – 10m, with coverage of 40m and 80m as well, although performance isn't fantastic on these lower bands.

The antenna is a vertical for the first 8m, supported on a fibreglass fishing pole. It then goes off at quite an acute angle down to the garden fence. The pole is held against a tree trunk with a couple of bungee cords and has a single earth stake. It is fed with RG213 coax with a 10-turn choke at the feedpoint.

What I did notice was that the antenna didn't work very well on medium wave, long wave or with LF aeronautical NDBs, so I thought about trying something.

The unun box now has a DPDT switch attached that switches out the unun and feeds the antenna directly. This has made a big difference to medium wave with signals romping in. The switch is waterproofed so all I have to do is go outside, flick it if I want to use the antenna on medium or long wave, and flick it back to engage the unun, which gives a better match on the upper HF amateur bands.

Without the unun I also get a better match on 80m, which is a bonus. Simon and SRC are no longer trading unfortunately, but you can build your own 9:1 unun quite easily.

While it is no Flag, Kaz or Wellbrook Loop, it does make a simple omnidirectional antenna for SWLs and hams.

PA0RDT Miniwhip – commercial and homebrew versions tested

The circuit diagram - you can easily make this on
a piece of PCB.
This has to be the ultimate in small antennas – one that will receive everything from VLF to HF (even VHF) in a package less than six inches long!

The antenna was conceived after Roelof, PA0RDT, had several attempts to make an active loop work in a city environment.

What he discovered was that the electric field from local noise sources was generally contained within his house. But, the magnetic field of noise sources was not, making weak signal reception at LF virtually impossible.

From that he decided that an antenna mounted outdoors that was receptive to the electric field rather than the magnetic field might be useful.

After extensive tests he said it became clear that at LF an active whip is effectively a “capacitance coupled to the electric field”.

Roelof added that in practice the “whip” can be tiny, such as a small piece of copper clad printed circuit board. Hence his Miniwhip was born. Roelof's practical design is only 100mm long and 40mm in diameter yet will receive from 10 kHz – 30 MHz.

It is an active antenna and that feeds the power to the antenna via the coax and a bias T circuit.

The antenna details and schematic are available on the internet for you to make one, but Roelof also makes them to order (you can email him at roelof@ndb.demon.nl). At the time of writing the cost was €48 including shipping within Europe.

The antenna and its amplifier circuit are built into a sealed grey plastic pipe leaving you only to connect a suitable length of coax via its BNC socket. You will need to provide a 9-15V supply, such as a small “wall wart” PSU. But it must be a “clean” supply as some of these can be electrically noisy.

Extensive tests with the antenna showed that it is very prone to receiving noise (which I had been warned about). In my shack it picked up all manner of interference, from switch mode power supplies to a low-energy light bulb. Even a TV on standby in a room 20ft away caused problems. To be fair, this was to be expected. Roelof says it is an excellent noise sniffer! He has used it extensively to investigate several local noise sources.

It is best mounted outdoors and as high as you can get it. In fact, I mounted mine on a telescopic fibreglass pole so that I could test it at different heights up to 8m.

The tiny commercial version, direct from Roelof.
Extensive use of ferrite chokes might also be useful. I found that my two PCs produced a lot of interference, which was picked up on my Perseus SDR receiver. Using my Icom 756 Pro 3 with the PCs switched off made a big different, especially on the LF/MF bands. Roelof says that grounding the shield of the coax before it enters the house or at the bottom of the mast is also important.

What happens is that local noise is received on the shield of the coax inside the house and travels to the antenna. By grounding the shield, the noise will "flow" to earth. This can make a considerable difference. He has also included a RF isolating transformer in the power bias T box. A jumper is used to select between isolated and connected grounds.

What also soon became apparent was that the higher I mounted it, the better the Miniwhip worked. In fact, at about 5m it almost matched the performance of my existing HF antennas, despite its tiny size.

Roelof says that moving the antenna from 1.2m to 4.8m could increase the received signal strength by up to 8dB on the lower bands and I would agree.

I tested it on everything from non-directional beacons (NDBs at LF), long wave, medium wave and all ham and broadcast frequencies up to 30MHz and it worked very well indeed.

Mounted on a fibreglass pole the antenna merrily received aircraft non-directional beacons down in the 300kHz range – signals that were considerably weaker on my main doublet antenna.

It was a similar story with medium wave stations, with the tiny antenna pulling in stations from all over Europe in August. My usual test is to see how well I can pick up BBC Radio Wales on 882kHz from Washford, Somerset, here in Norfolk. It did this with flying colours.

Moving up to Top Band (160m) and there wasn't a lot of activity, but I did pick up some DL and PA CW signals that were at least as loud as those received on my W5GI antenna over the roof.

It was similar performance on 80m (3.5MHz) where the little antenna worked reasonable well, but was down on a dedicated 80m antenna. Noise levels were a lot lower though. On 40m (7MHz) the antenna also picked up signals, but the signal levels were down quite significantly. Interestingly, in some instances, the overall signal to noise ratio was no different, so in terms of copying the signals there was little difference.

My own version built (very) ugly style and now
mounted in a piece of 40mm PVC pipe. 
Roelof says that he has his mounted at 4m on a non-conductive mast to get clear of bushes in his garden, but he has also had excellent results in an open field at a height of only two metres.

The Miniwhip makes an excellent SWL antenna, as long as you spend some time calming all the various noise sources in your shack.

I even mounted it in the loft, where it worked, but again noise levels were higher.

In the interests of experimentation I also decided to build one myself from the plans I found on the internet.

The antenna is made on a piece of single-sided PCB, with the top half acting as the antenna and the lower half holding the circuit. I made my circuit board by carefully cutting away the copper with a Dremel-type tool. I then built the circuitry “ugly-style” (very ugly actually!) onto the board, using Superglue to mount some of the components securely with their wire leads being used for the interconnections. The end result was a little Heath Robinson, but did it work? The answer was a resounding yes.

As a test I also tried it on VHF and found it was a reasonably effective little antenna for airband and 2m signals.

Overall then, if you have no means of putting up an antenna for Top Band, and are also interested in LF, NDBs and medium wave, this tiny antenna will let you listen to all the action.

Monday, 19 May 2014

An Introduction to Antenna Modelling

Just a quick reminder that my new book "An Introduction to Antenna Modelling" is now available.

The book looks at the free MMANA-GAL antenna modelling program that lets you design and optimise a whole host of antennas – all on your PC.

It shows you step-by-step how to input antenna designs into MMANA-GAL, how to adapt designs you are given and how to optimise your designs for the best performance.

By the time you have finished you should be able to model a whole host of antennas including dipoles, the G5RV, the W3DZZ trapped dipole, verticals, off-centre fed dipoles (OCFD), magnetic loop antennas and many more.

The book also includes a CD-ROM that not only contains the MMANA-GAL software so you can get started immediately, but sample antenna files too. It also includes other antenna modelling software including EZNEC, MININEC Pro and 4nec2. Plus there are also more than 30 other amateur radio programmes included.

The RSGB has also managed to keep the price below £10.

See the RSGB shop.

Saturday, 22 March 2014

28MHz (10m) beacons still romping in

Predicted 10m propagation at 1600UTC March
Had an interesting hour or so listening for 28 MHz beacons this afternoon.

Despite the VOACAP prediction suggesting that there would not be much propagation into the USA from the UK on 10m, there were plenty to be copied.

I think 10m propagation to the States will start to disappear as we move towards summer.

I even heard two from California.

I like beacons. They are usually low powered, use single element antennas and the beacon owners appreciate a quick e-mail to show that their efforts are worthwhile.

You can find G3USF's list of 28 MHz beacons at http://www.keele.ac.uk/depts/por/28.htm

Anyway, here is what I heard, all with a dipole:

CALL COMMENT FREQ
N2PD/B New York, 5W 28.285
WA4ROX/B Florida 28.286
W3APL/B Maryland, 8W 28.296
K5TLL/B Mississippi, 25W 28.298
WI6J/B California 28.287
K5AB Texas, 20W 28.280
WF4HAM Florida, 10W 28.273
EA7JN/B 28.258
W6WTG California 28.287
WA2DVU New Jersey 28.257
SV2AHT/B KN10NO, Hortiatis 28.235
IQ8CZ/B Catanzo, Italy 28.230
SV2MCG/B Greece, KN10FC 28.222