Antenna expansion

I know when summer is here when I have to keep on tweaking the tuning of my MFJ magnetic loop antenna throughout the day. Having an antenna farm in the attic (or loft as it is more commonly called over here) protects the antennas from the depredations of the elements but it does subject them to extremes of temperature during the summer months. As the loft warms up during the morning the metal of the magnetic loop expands. Because the magnetic loop is a very sharply tuned antenna this has an effect on the SWR. I don't know what the temperature in the loft reaches on a sunny day but I wouldn't want to go up there.

I'm not talking about a small change. I may tune the antenna to achieve a 1.2:1 SWR first thing in the morning and by lunchtime it can have increased to 2:1 or more. This wouldn't be so noticeable if I was moving around the bands retuning as I go. But I use the magnetic loop for my 30m APRS station which stays on 10.1473MHz all day and every day. (It does a jolly good job there, by the way.) If I don't pop into the shack now and again and give the antenna a quick tune I could be subjecting the transceiver to a higher SWR than is good for it.

The magnetic loop is the only antenna I have that will cover 30m, so I don't have any alternative for my APRS system. This need for retuning affects all the bands I can use the loop on, not just 30m.

I suppose my multiband dipole also expands and contracts with temperature, but because the tuning is broader the effect on the SWR is less noticeable. Outdoor antennas have their tuning affected by rain or ice, of course, so I'm not alone in having to put up with weather effects on my antennas.

Tripod for a WalkHam

Having got an AlexLoop WalkHam antenna I needed some way of holding it up whilst it was in use. After considering ideas like a guyed mast made from plastic pipe I decided the best solution would be a photographic tripod, if only I could devise a way of mounting the antenna on it.

After scouring eBay for a suitable tripod I came across this one from British firm Strand Europe. Unfortunately this won't be much help if you're not in Britain as the seller will only post to the United Kingdom.

The tripod is short enough when collapsed to fit inside the WalkHam carrying case - the stumbling block for most of the ones I looked at which were just a bit too long. What's more, the panning handle can be secured in the vertical position and fits inside the WalkHam's mounting pole like it was made for it! So no modifications are needed and you can still use the tripod for photography if you want.

The same day that the tripod arrived I received an email from Alex giving details of his own tripod recommendation. He wrote:

"The perfect tripod is the VIVITAR VIV-VPT-1250. It is a 50'' unit and the lightest and most inexpensive VIVITAR unit that can be found for less than U$ 10.00. The secret is take off the camera head with a Phillips screwdriver and leave the aluminum tube on the top. It must be  marked with a pencil at 4 inches (12 cms): that is the maximum extension that can be used to introduce something to avoid any pressure on the antenna elements. Without the camera head the tripod can be collapsed and carried inside the antenna bag."

I couldn't find the Vivitar for as little as $10 in the UK so I'm content with my purchase. My only reservation is that the tripod is much lighter than the antenna (a good point for the person carrying it of course) and might be inclined to blow over if used in much of a breeze. I'll find out when I manage to try it! I can't say whether Alex's recommended model would be any better in that respect.

AlexLoop teams up with KX3

Just a few days after I wrote that the AlexLoop WalkHam is a great companion for the Elecraft KX3 and here is a video by Steve WG0AT showing the combo in action.

5 and 9 using QRP SSB! I can't wait until I'm fit enough to take the KX3 and loop to the outdoors myself.

Looping the loop

Whenever I have taken a rig to operate in the Great Outdoors using a wire antenna I have often been disappointed. This is probably due to my use of inadequate antennas - Miracle Whips and the like. When I have tried wire I usually fail to get it up high enough. Usually when hurling a rock attached to a string into the trees, the rock rebounds off a branch and narrowly avoids hitting me on the head. If I do manage to get it up high the rock irremovably entwines itself with a branch just out of reach. There has to be a better way!

AlexLoop WalkHam carrying case

I have long been an enthusiast for magnetic loop antennas and have often wished I could use one as a portable antenna. My Wonder Loop was an attempt to make such an antenna, but it was less portable than transportable (by car) and has seen more use as a spare antenna from inside the shack.

I looked longingly at the WalkHam made by Alex PY1AHD and wished I could make a portable loop as neat and compact as that. If I had to make it myself it might never get done so I decided to bite the bullet and buy one of Alex's ready-made loops.

There are two versions of the AlexLoop. One is a kit using copper tube  for the radiating element and costs $199 US. The other version, called the WalkHam, uses stout coaxial cable for the main loop and comes ready built in its own custom made carrying case similar to a laptop case. The price of the AlexLoop WalkHam is $299 US. Shipping to the UK by express courier to the UK is a further $82 US. The total cost to me using PayPal was just over £250 at the present exchange rate.

AlexLoop WalkHam in its case

 The WalkHam is well made with gold plated connectors for the loop element. It is easy to assemble, though not so easy to pack away unless you have a photo to show how the parts go back! The mast is made of black plastic tubing and is in three push-together sections. Once assembled the antenna may be used whilst held aloft - hence the name. Most users will probably prefer some sort of mast.

The AlexLoop WalkHam ready for use.

The loop is 1 metre in diameter and tuned using an air spaced variable capacitor with a 3:1 reduction drive giving a 4 : 1 tuning range: 10m - 40m. Most magnetic loops including home-made ones only manage a tuning range of 3:1: 10m - 30m or 15m - 40m. My MFJ magnetic loop is the 40m - 15m version as it was bought during the last solar minimum when 12m and 10m were not much use!

The coupling loop has a diameter of about 20cm. The maximum power handling is 20 watts PEP, 10 watts continuous wave, making the WalkHam perfect for use with QRP radios like the FT-817 or Elecraft's new KX3!

Tuning as expected of a magnetic loop is extremely sharp but I noticed little or no hand-capacitance effect. With a little practice the loop can be tuned by peaking for maximum noise in the receiver. If the SWR isn't low enough then the tuning may be touched up using transmit and the rig's built-in SWR meter if it has one (both the FT-817 and KX3 do!) If not, a simple SWR indicator as I used in my Wonder Loop would be a big help.

Subjectively the AlexLoop seems to work as well as my MFJ magnetic loop in the attic, which itself is comparable to a full-size dipole. There are not many portable antennas that would beat the AlexLoop WalkHam for performance, unless you are able to erect a couple of 40-foot masts!

One thing that would improve the package would be a way of erecting the antenna so that it will stand on its own. I think my arm would soon get tired holding the WalkHam aloft! Possibly a short guyed mast made of sections of electrical conduit would do the job: magnetic loops don't need to be far above ground in order to work. Some users are reportedly using photographic tripods so I'll probably investigate that in due course.

Sivan's Wonder Loop

It's always good to hear when something one does or writes inspires somebody else to try it and they are pleased with the outcome. Sivan, 4X6IZ, made a version of my portable Wonder Loop and found that "it works as advertised." He has put some information and pictures of it and another loop he made on a website. His idea of using polyethylene coated aluminium pipe to make a fixed frequency loop and tuning capacitor is particularly interesting if you always operate close to a particular frequency such as for QRP CW, PSK31 etc. If I had space in my attic for another magnetic loop I could dedicate for HF APRS use I would definitely make one of these.

I'm sure you'll find it worth reading about Sivan's magnetic loop antennas.

A QRP Evening

Yesterday the four visiting Norwegian QRPers Mads LA1TPA, Aage LA1ENA, Halvard LA1DNA and Kjell LA1KHA came to visit us.

We had a very pleasant evening. On learning that my wife Olga was from Ukraine, Kjell greeted her in Russian and was interested in her thoughts about what life was like in the Soviet times.

Amongst other things we talked about about QRP radio, operating from summits, trouble with neighbours and difficulties getting permission to put up antennas. It is not just in the UK that we have these problems. Two of the guys had no home station antennas at all, and Mads has just an MFJ magnetic loop at home.

The guys were interested in seeing the HB-1A QRP CW radio from China, and also my Wonder Loop home made portable magnetic loop antenna. In the picture, Kjell is trying to make a contact on 30m using the HB-1A and Wonder Loop. He was not successful, despite received signals being strong, but perhaps our aluminium-framed conservatory was acting as a Faraday shield. Despite that, Aage was interested in getting an HB-1A and Mads said he plans to make his own version of the Wonder Loop.

The evening was a success and it was nearly midnight before they left for their hotel in Keswick. I'm glad to say the Lakeland weather has been kind to them, and today is fine and mild for their last day in the Lakes.

An Italian for lunch

Just after lunch today I had a tune around on the little guy, the HB-1A QRP CW transceiver. On 10.116MHz, the 30m QRP activity frequency, I heard Steve, IK6NHA calling CW at about 18wpm with long gaps between the characters, so I gave him a call.

Conditions on 30m this afternoon seemed very unstable. Steve's signal was hitting S9 on the little Chinese radio's meter but with sudden QSB down to the noise level. Steve gave me a 229 report and asked me to repeat my call, though he did get it right the first time. He got all the other details I sent too, which is good going as it turns out he was running 100W. I was running about 4W to the MFJ magnetic loop with the HB-1A on batteries and I was struggling to hear him at times.

Steve's QTH is a town called Tolentino, which I guess is up in the mountains somewhere as the temperature was 7C, colder than it is here (and it's a grey, rainy day today.)

I love Italy. The whole place looks like it is falling down, nobody has heard of DIY and nobody seems to care either. What a great attitude! So different to England where the sound of lawnmowers and pressure washers is never far away and people seem to spend the whole weekend painting and cleaning instead of relaxing and enjoying the rest they've surely earned.

Voices from space, whispers on 80

It was one of those crystal clear evenings when the stars shone like jewels from a black sky. N2YO's satellite tracking site showed that the Space Shuttle would pass over at about 9.20pm at magnitude -2.0 - brighter than Jupiter - so my wife and I went out in the garden to watch it. Olga spotted it first, rising over the roof of the neighbour's bungalow.

I had the VX-8E tuned to 145.825 to see what APRS I could catch, but nothing was heard, so I flipped down a channel to 145.800 and heard an astronaut's voice, clear as a bell. We only heard one side of the conversation, but it was still quite something to watch the space station go over and know that the person talking about why he had wanted to become an astronaut was actually in that bright, moving star, up there.

Meanwhile, up in the shack, my FT-817 was doing some WSPR testing on 80m using my Wonder Loop magnetic loop antenna. To get it to tune 80m I connected an 820pF silver mica capacitor across the loop / variable capacitor terminals. The tuning was nice and sharp, and although the SWR did not seem to be particularly low it only raised one bar on the FT-817 meter.

There were not many people on 80m WSPR but I was consistently received by LA2XPA, while I received G7JVN several times. For comparison I replaced the Wonder Loop by the ATX Walkabout and received two more spots from LA2XPA at similar signal strength. I also put out a number of CQs using 5W of PSK31 but got no replies. I wasn't even spotted on the PSK Propagation Reporter site.

I didn't really expect the small Wonder Loop to work very well on this band. However, earlier in the day I had stumbled across a site I hadn't seen before showing a small diameter magnetic loop with plug-in tuning modules covering 160m to 6m, so I was interested to see how far I could extend the Wonder Loop's coverage.

Busy, busy

I'm going to be taking a bit of a break from radio this month. I'm going to be rather busy between now and the end of August, and if I do find the time for some radio activity I may not have the time or be in the position to blog about it.

However I did manage to find the time to finish the article describing my Wonder Loop. Enjoy!

SSB a struggle

There is an IARU contest on this weekend and the thought occurred to me that this might be a good opportunity to try to make some SSB contacts with the Wonder Loop and FT-817ND. It started well enough on 20m when S53M came right back to my call and completed the contact without difficulty. A few minutes later DJ1AA was in the log - I had to repeat the exchange a few times and make sure he logged my call as ILO not LLO, but he got it in the end. But after that, nothing. One station copied me as G4LLO and gave up after failing to get the year of my license. Another heard that a G4 was calling, but that was all.

I think conditions must have been extremely poor. I cannot recall a contest where no stations were above S9 on the FT-817 meter.

I then decided to try my K2 to get a bit of extra power - 10W instead of 5W. But it was as if I was not there. I started to wonder if something had gone wrong with the Wonder Loop so I took the feeder from my multi-band dipole and plugged it into the K2's other antenna socket. But there was very little difference in signal strengths between the two.

While tuning around 40m I heard DJ2OD calling CQ on CW, so I plugged my Russian straight key into the K2 and called him on the Wonder Loop using 5 watts. He came straight back to my call, gave me a 579 report and we completed a QSO. No hassle, no frustration!

CW Rules!

Wonder Loop on 40m

Last night I had a bit of time to try the Wonder Loop on 40m. Again, I used 5W of PSK31 so I could use the Propagation Reporter Network to see where my signals had been received.

Once again, the Propagation Reporter map does not give a full indication of how far my signals travelled, as there were only 10 monitoring stations on 40m at the time and some of them may not even have been in Europe.

My first contact was with Billy, 2E0WJC in Leeds, who was also running QRP. It was a solid contact with almost perfect copy. Later on in the evening I worked Gordon, G4TZX near Dover, for another good chat. I was then called by Frank, DL7LAX in Leipzig. There was some QSB but we managed to complete a contact. Finally I worked Kari OH2LRG/4 who had difficulty believing that I was using an antenna inside the shack. Most stations I have worked using the Wonder Loop are amazed that I am using an indoor antenna and want more details, so I end up having a chat instead of just the usual exchange of details.

I am very pleased with how well the Wonder Loop works on this, the lowest band it covers. For Kari and others, I should be starting work on the description of the Wonder Loop very soon now.

Some 30m test results

Last night, between the end of one BBC Promenade Concert broadcast and the start of another, I managed to spend half an hour on 30m PSK31 with 5 watts and the Wonder Loop. The map below shows the results from Propagation Reporter just before I closed down.

Not as impressive looking a map as the one on 20m this afternoon, but it was only for half an hour, and 30m is not as busy a band so there are fewer monitoring stations. However, conditions seemed better, received signals were stronger and I received replies after fewer CQs. I made two contacts into France and was also called by a station in the Czech Republic who disappeared after I sent my first over so it didn't count for a QSO.

Something that went unremarked in this blog at the time is that on 25 July a 2 watt WSPR signal into the Wonder Loop on 30m was received by Myles, VK6ZRY in Western Australia (who, incidentally, was also using a magnetic loop antenna!)

I think these results show the Wonder Loop radiates a good enough signal on 30m to make plenty of CW or digital QSOs. Next I will try 40m.

PSK31 contacts

Today I thought I'd try to make some PSK31 contacts using the QRP Wonder Loop. Because the mouse pointers go berserk on both of my laptops when in the presence of a strong RF field, I had to use the main shack computer and therefore the K3. But I turned down the power to 5W p.e.p, which is what I would run if I was using the FT-817 or the K2, although the tuning capacitor I used could easily handle 10W, and perhaps even more.

The picture shows the map displayed by Propagation Reporter after I had been on the air for three hours or so on 20 metres during the late morning and early afternoon. For those unfamiliar with the display, the small markers show the stations that had been received on the Wonder Loop and decoded by Fldigi. The large markers with a time interval show the location of stations that heard my transmissions, and how long ago they last reported me. These stations would have needed to receive "DE G4ILO G4ILO" without errors in order for their software to submit a report, so the large markers represent stations with whom it would have been possible to have a QSO. The concentration of large markers in Western Europe may in part be due to the fact that fewer people in Eastern Europe have a broadband internet connection, without which propagation reporting is not very practical.

It has been more than a year since I last operated QRP PSK31. I got the 100W PA for my K3 because I was starting to find QRP a bit frustrating after the many years (it seems!) of poor conditions. So I had forgotten that PSK31 with 5W can be a bit hard going.

I called CQ most of the time because that gives the best chance of being spotted on the Propagation Reporter network. Although a couple of dozen stations heard me (as you can see from the map) only two replied to my CQs. I made one other contact, with DB7HH, which was in reply to his CQ. Normally when working QRP I would search out other stations and call them, which would probably have resulted in more contacts.

I think the Wonder Loop performed well in this test. I think the difficulty in making contacts was mainly due to the poor conditions. There were no really strong signals during the period of the test. Although the results might not show it, I felt that the loop worked well enough that it would not be too bad if it was the only antenna I had. In fact, it's working better than I expected.

First contacts

I made the first actual contacts using the G4ILO Wonder Loop today. I hooked it up to the 1 watt MFJ Cub on 20 metres. The Wonder Loop is actually the only antenna I can use now with my QRP rigs on 20m due to the extremely high noise I get on that band. It has a very sharp null at right angles to the plane of the loop, which can be used to reduce the QRN to an acceptable level.

I was very happy with these first contacts. Onno, PA1AP calling CQ near the QRP frequency 14.060MHz came back to my call on the second attempt. Perhaps he would have come back the first time but I called a bit off frequency. He gave me 519 and struggled a bit to hear me but he was actually using 100W at his end. Manuel ON/DL9EBG then called me when I signed off with PA1AP. With my style of operating that almost constitutes a pile-up! He gave me 529 but later amended the report to 579 with QSB. He was running 5W from an IC-703 and was a good signal - I gave him 599 which is what it sounded like in the little Cub receiver.

I think this shows that the Wonder Loop is an effective antenna that will get you contacts even when used indoors with only 1 watt of power. I was going to try using the FT-817 or K2 and a bit more power but found that my QRP keys were incorrectly wired for those radios. I'd wired the ring of the stereo jack to the shield thinking that this was more like the mono jack you'd expect to use with straight keys. But both rigs went key down when I plugged in the jack, so I had to rewire them so there was no connection to the ring.

After I had done that I noticed that there was a good Sporadic-E opening on 6 metres favouring eastern Germany and Poland, so I cleared the QRP gear away and fired up the K3. I made several contacts into Berlin and the surrounding area and one into Poland. I didn't hear many DX stations calling but a fairly local GM was working strings of stations at good strength, so I parked near his frequency and called CQ. This netted a few extra contacts, including the one with SQ5AXS, and Peter DL2FI who called me on CW! I was a bit surprised to be called on CW while working SSB. Peter's call rang a bell but I didn't remember why (he is a fellow Elecraft user and runs the German QRP Club) until after the contact. Sorry, Peter. I'm getting a bit slow in my old age!

Postscript: I just noticed while checking the stats in my KComm logger that I have now made 200 contacts on 6 metres with more than 100 different grid squares. That is the greatest number of contacts I have made on any band except 20 metres. I would never have believed it.

Size matters

What a difference an extra 14 inches (36cm) makes! I'm referring, of course, to the diameter of the radiating element of a magnetic loop antenna. I replaced the 40cm diameter loop of my Wonder Loop with a 76cm (2ft 6in) diameter loop made from RG-213 coaxial cable. Suddenly its performance is transformed from unquestionably poor to very impressive. Early tests show this is a desktop antenna that will blow Miracle Whips into the dust and give results not much worse than a full-sized dipole!


The revised antenna is somewhat larger and bulkier than the rather neat original. Accommodating the bigger loop created a few problems. An important factor in the design was to make antenna that can easily be taken to bits, packed up and transported in a suitcase or backpack. It was also intended to be free-standing. Therefore the support and loop need to be detachable and the loop has to be made of wire so it can be coiled up for transportation. The use of copper tube was out of the question - though obviously an option for constructors wanting to make a magnetic loop for home use only - while the solution adopted by G4TPH of using short lengths of aluminium strip bolted together to make a dodecahedron seemed cumbersome.

A length of uPVC electrical conduit was cut for the support, and a 240cm length of RG-213 was cut and the braid at each end soldered to two gold plated 4mm spade terminals. 80cm of stout wire was cut for the coupling loop. Because the cable would need to be removed from the support it is just hooked to the top of the support, and a self adhesive cup hook was attached to the top for that purpose.

The most obvious problem after hooking the cable to the support and attaching the terminals to the binding posts on the tuner was that RG-213 does not have sufficient stiffness to hold a circular shape in such a large loop. The shape could best be described as that of a saggy backside (younger readers may have to wait a couple of decades to see what I mean by that. :) )

Despite this, the antenna still pulled in some pretty strong signals, so I set it up with the FT-817 on 30m WSPR for testing and went downstairs for a cup of tea with the XYL. While we were half way through our tea we heard a crash from upstairs, and rushed to investigate. The self adhesive pad used to secure the hook had given way, allowing the loop to crash to the desk, leaving the FT-817 to transmit (of course, this happened during a transmit period!) into a virtual short-circuit. Fortunately, the radio survived the experience!

The support was re-made using superglue to attach the hook to the mast. I also solved the saggy backside problem by gluing two more hooks to each end of a length of the back part of the uPVC conduit. This sits resting on the top of the loop support, hooked round the loop on each side. The uPVC back strip is thin enough to curve slightly under the weight of the coaxial cable, allowing the loop to be more of a circular shape. It's a bit Heath Robinson, but it looks better and more importantly helps the antenna work better, because the ability to tune to a 1:1 SWR is dependent on the position of the coupling loop with respect to the main one. You can see this support piece in the photo, which shows the Wonder Loop sitting on top of the 2m transverter while I was making some initial tests on 30m WSPR.

One effect of using a larger loop is that the frequency coverage has changed. Whilst the 40cm loop covered 30m thru 10m, the larger one covers 40m to 15m.

Initial A/B receiving tests with the Wonder Loop positioned as shown in the picture compared with the MFJ magnetic loop in the attic above it suggest that on 40m it is down about 6dB compared to the MFJ, on 30m it is about equal, and on 20m received signals actually seemed a bit stronger.

As shown in the photo the Wonder Loop was only a few inches from the wall and also a conduit carrying two of my cables up to my attic antenna farm, but it actually tuned up on 30m in that position to give a 1:1 SWR. I then did over an hour of A/B testing using WSPR on that band. The results were interesting. My signals were copied well in Europe and even by several east coast USA stations. I was consistently getting reception reports 10dB higher from IK2CMN and IV3DXW when using the Wonder Loop than when using the MFJ! Some reports from other directions seemed a few dB lower, but reports under identical conditions from the same stations at different times can often vary by 10dB or more due to QSB so it is hard to attribute such small variations to the performance of the antenna.

These are not scientific tests, as the two antennas are in different positions and may be subject to different coupling effects or reflections from other objects. Nevertheless I think the point is made that the Wonder Loop with 76cm diameter element performs extremely well for an indoor desktop antenna.

I will be doing some further tests on as many as possible of the bands the Wonder Loop covers (it's hard to find any propagation on 17m or 15m so testing on those bands is difficult.) As time permits I shall also attempt to make some QRP contacts with the antenna. But I am extremely encouraged by the results so far, which suggest that this portable magnetic loop could equal or even outperform typical portable QRP antennas such as random wires, loaded verticals and low slung dipoles, while avoiding the need for supporting masts, ground wires and counterpoises.

Alex goes professional

As an enthusiast of magnetic loop antennas, one of my favourite websites has long been that of Alex Grimberg, PY1AHD. I decided to visit it again today whilst doing a bit of research to find out whether, if making a magnetic loop out of coaxial cable, the inner should be connected to the outer shield or left disconnected. And I found that since I was last there Alex's site has had a professional makeover.

What was even more interesting was that Alex has decided to release a portable magnetic loop commercially. Called the AlexLoop SML 7-30, it is a small portable magnetic loop that covers 40m to 10m and is intended for QRP use. Supplied as a kit, you get a hand-held mast with a rubber holding grip, near which is mounted a box containing the tuning capacitor. The loop itself is formed from a length of flexible thin wall copper tubing which must be soldered to the variable capacitor and then secured to the mast with cable ties.

Apart from the fact that it is hand-held rather than table standing, doesn't have a built-in SWR indicator, uses a fixed size loop and is not apparently easily dismantled for packing and travel, the AlexLoop looks pretty much like what I am trying to create with my Wonder Loop. I would guess that the bits to make one could all easily be purchased for less than $30, which is about what I've spent on my antenna. So I was dumbfounded when I clicked the Buy Now button to find that the AlexLoop has a regular price of $219, though if you act now you can get it at an introductory price of $179, with postage to Europe adding a further $72!

Spurred on by the thought that my Wonder Loop could be the idea that will earn me that long-deserved fortune, I continued my researches and decided to do some more experiments. I never did find out whether it is better to connect the inner of the coax or not when using it to make the main element of a magnetic loop antenna. Some constructors do, others don't, and many more don't specify. I did find a couple of sites that said a thicker element improves efficiency, so I decided to re-make the 40cm diameter loop using an odd length of RG-213 coax. However, it didn't seem to perform any better on transmit than the one I made using 10A PVC covered wire. It seems that I'll have to make the loop at least twice the diameter to have a chance of radiating a decent signal. Hopefully I might manage to try that tomorrow.

WSPR while you work

DIY is one of my least favourite activities. If any major job needs to be done around the house, I'll get someone in. However, this is Britain, the country where everyone wants to get paid for sitting on their backside instead of learning a trade and getting their hands dirty. Good painters and decorators, joiners, plumbers and electricians are hard to find, and usually booked up months ahead (or on one of their biannual holidays in Barbados.) If they aren't booked up months ahead they are probably either cowboys or East European immigrants who are happy to get off their backsides and earn a living but may not have any actual painting/joining/plumbing/electrical qualifications. So if you need something done quickly and don't want to be ripped off or featured on "Homes from Hell" there is often no alternative to doing it yourself.

Having just had a conservatory built there were some finishing-off jobs that needed doing now, so having just finished making my Wonder Loop I couldn't spend any more time on the radio. Instead, I set it up on WSPR and left it. This was probably a good thing, as it enabled me to get an objective view of its performance. Unfortunately the objective view is that it doesn't work as well as I hoped it would.

Although my 1W signal on 30m was heard as far away as Poland, and I even received signals from the East Coast USA, results on 20m, 17m and 10m (the only other bands with enough WSPR monitors to be worth trying) were disappointing. Nothing at all was heard on 10m, although another G station was active and being received. 20m was difficult to test due to the interfering presence of RTTY on the WSPR frequency band. I was heard in Germany on 20m, but weakly and not very often

Reports on 17m were also disappointing - so much so that I switched to the ATX Walkabout for comparison and received reports more than 6dB better. The ATX Walkabout is a great little antenna for both the size and price. Anything that can't outperform it isn't worth using.

The Wonder Loop is a good receive antenna. It is much quieter than the vertical ATX and has a sharp null axially through the centre of the loop that allowed me to reduce the QRN I'm plagued with almost to nothing. But clearly it needs to be made more efficient. The 40cm diameter loop is a convenient size, but whether it is just too small, or whether efficiency could be improved by using thicker wire or some heavy co-ax for the radiating element is something that will have to be determined by further experimentation when I have more time to spare.

The Wonder Loop

Today I finished a project that has been on the go for some time - the G4ILO Wonder Loop. The idea came to me several months ago while testing the Wonder Wand antenna. Regular visitors to the site will know of my interest in small, very portable HF antennas that can be set up without any supports, even indoors. Most will also know that these very small antennas tend not to be very efficient. I have been extremely impressed with the performance of the MFJ Magnetic Loop antenna, and wondered if a magnetic loop would make a better "wonder" antenna than trying to use a short telescopic whip. How small could you make a magnetic loop and still get better performance than a Miracle Whip or Wonder Wand?


The Wonder Loop is an attempt to make a QRP version of the MFJ Loop Tuner. Essentially it's a project box containing a variable capacitor whose terminals are brought out to two 4mm binding posts, to which are attached the two ends of the loop radiating element. The small coupling loop plugs into an RCA socket which connects it to an N7VE QRP SWR indicator built into the box. I'm grateful to one of my blog readers, Steve Silverman KB3SII, for this. Steve sent me the one he bought at Dayton after reading of my frustration when QRP Kits sent the wrong kit, thereby enabling me to complete the project. The transceiver plugs in to the BNC socket on the side. I'll probably publish more details, photos and results in the main part of the site later on, once I have done more tests.

The neat thing about the Wonder Loop is that it is very compact for transportation, because everything detaches from the box. You can also use loops of different sizes, for different frequency coverage or to get better efficiency at the expense of larger size. The loop support is a length of uPVC electrical conduit. The loop itself could be made of stout wire or coaxial cable.

Currently I'm using a loop just over 40cm in diameter, which gives a tuning range from 30m to 10m. It's on test using my FT-817 and WSPR as I write, with the Wonder Loop sitting on my shack desk, just like in the photo. So far my 1W signal has been heard in Germany by two stations on 20m, in the UK and Germany on 17m, and in France, Germany and Holland on 30m. Not bad in just an hour and a half!

Plans include trying an 80m loop, and one for 6m. So watch this space!