The M1GEO Wellgood Active Receiving Loop antenna was developed by Dr George Smart M1GEO following accidental damage to an existing loop antenna he owned.
Interesting information about the development can be found here Wellgood Loop History Page
George decided to release his design and share it amongst the radio community.
The wellgood SWL receive loop is supplied as 2 populated PCB boards and a 1 page of guide notes.
The way in which you can deploy this antenna has so many variations and possibilities. Indoor or outdoor mounting, choice of element medium and so on,
It is entirely the decision if the buyer to supply the loop element and any enclosures, fixings etc.
Details of the current kit supplied by George can be found Wellgood Loop project page
The 2 PCBs kit were supplied at a cost of £37 to UK including postage. International (outside UK) post rates will be more.
To order the kit, send initial email to the designer and seller Dr George Smart M1GEO stating your requirements and Geo location.
George is a very busy person with work commitments especially weekdays, he supplies these kits on a time allowing/hobby basis, Please be patient.
Here is a photo of the kit (v3.1) showing the Loop amplifier and bias tee PCBs.
The circular active amplifier PCB has been cleverly designed to fit into a standard round PVC electrical conduit box (AKA Besa Box) should a user wish to choose this option. The cut outs match perfectly.
Searching the internet, I found another user in the UK Stephen M5SJM ( web page linked below for reference) who had chosen this mounting option.
I was building this antenna for a friend who already had a 20mm diameter steel pole mast installed in their garden, a 25mm could slide over that nicely.
I had to think of a solution to outdoor installation.
Below was my original idea, to construct a plate for the amplifier box and support frame out of 25mm PVC electrical conduit tube and use a 1 mtr diameter coax loop element.
Following much thought & experimentation with the design above the loop element had a tendency to sag and move about in bad weather.
Initial ideas I had are illustrated below.
Single Turn Loop (Using centre and braid combined acting as one copper element).
2 Turn in series loop. (Using centre and braid as a continuous winding)
A solution for a support structure was found by using a ≈ 90cm Ø hula hoop to support the coaxial loop.
The Hula Hoop was an 8 section take apart /transportable ≈92cm Ø weighted/exercise type and it originally had foam covering which was removed very easily with minimal tools. The 8 sections interlock using spring loaded metal plungers.
The coaxial chosen was RG-8 from Davis RF in the USA.
After extensive indoor trials and much take apart & reassembling it was discovered that the plastic hoop female ferrules started to came apart under heavy stress so I reinforced them with resin and aluminium tape. This improved rigidity immensely.
Satisfied with the hoop support I moved on to making the plate for the amplifier PCB.
A piece of 3mm thick aluminium plate and suitable IP66 enclosure Schneider-Sarel NSYTBS885 , here are the dimensions /details.
Markings for drilling the holes in the plate with the outline of the enclosure in the centre.
Next, the drilling of the enclosure to accommodate SO-239 , BNC from amplifier PCB and venting valve.
You should think about the location of the power on LED , it is an SMD package on the back of the PCB. Perhaps you may wish to mount the amplifier board with the back facing forward towards the lid ( in my case the orange power on led provided enough reflected light to see if it is active even though it was on the back of PCB).
Caution with the vent valve hole, The plastic hexagon back nut is quite large and it can interfere with the corner of the inside of the enclosure. Take care measuring and allow for this. If using this exact enclosure you will end up with the BNC and vent / air balance valve hole quite close to each other.
You can see here the close proximity of the vent valve locknut to the fixing post for the lid of the enclosure hence the “heads up”.
Fixing the enclosure to the plate with a pair of M4 X 20mm A2 Stainless Steel Hexagon Machine Screws, A2 washers and A2 nylon locknuts.
For preventing short circuits/ pcb to bolt head contact I used clear silicone sealant as glue for a neoprene gasket from a circular electrical conduit box.
Drill the 3mm fixing holes for the flange type SO-239 and fit m3 x 16mm stainless steel socket cap screws, A2 washers and A2 nylon lock nuts.
Note that M3 socket cap screws have a 2.5mm hexagon head.
The wire links were made from 18awg ptfe teflon coated silver plated avionics wire with soldered ring terminals.
I measured the links carefully so that the pcb could be removed from the enclosure with links attached and the back of the pcb and its locknuts could be accessed for easy maintenance.
NOTE : I used clear silicone at location of L1 bobbin inductor to bnc casing marked by the arrow. You could use hot glue here instead. I found that it is very easy to bend the legs of L1 accidentally when putting the PCB in and out of the box. L1 legs are soldered to the top of the PCB only. The component is not a through hole type and the legs could snap off if you are heavy handed. Be warned.
This 4 hole flanged type was selected as a chassis SO-239 only has 1 large locknut and tag which would have a tendency to become loose when installing/uninstalling the element PL-259 plugs. As the element will be the coaxial braid and good electrical contact at this point is essential for normal trouble free operations, a chassis type of so-239 connector was omitted.
I selected compression type PL-259 connectors & in an attempt to get as much copper in the air as possible I chose Davis RF/ Orion RG8-U coaxial which provided very good copper braid coverage (97%).
The hula hoop was placed on top of the enclosure and some wire ties (made from stripped down CAT5e solid cable) used to position the coaxial loop and fix the hula to back plate for initial testing on a pvc mast at low level in my garden.
Standard TV mast M8 v-bolt positions shown around the back.
I did think about and try out a 2 turn loop element using both the braid and centre core.
The performance was great (slight improvement on single turn although more directional) but as this unit was going to a user who was not familiar with soldering or electronics maintenance I decided on a single turn element for less connections and less chance of mishaps.
Here is the detail for a 2 turn series loop in case you want to try that configuration. Just 1 additional link wire required.
So I went for a single turn loop.
Moving on to the bias tee PCB. Dimensions and connection options are shown below.
Yes the box was far too small !
I made this selection for the enclosure bias tee enclosure
85mm x 55mm x 30mm, a little large but it was cheap to buy.
There is an additional place on PCB to mount a power on LED marked D3.
A 2mm lighthouse type LED seemed a good choice, a very small mounting hole with minimal intrusion.
I tried a few colours, the user decided on the blue option.
For the power, there is a 3 hole footprint on PCB for a standard 5.5 x 2.1mm which I mounted as a backup for the end user . Also there are 2 additional holes for +ve and -ve so I decided to use these with some wire tails out to a 5.5 x 2.1mm DC line socket
Power in is 12v DC centre positive.
Bias tee box completed with power supplied from a regular 12vdc “wall wart” switch mode AC-DC adaptor.
A Linear supply PSU unit would be even better. The blue LED was a good choice !
Using a take apart hula hoop made it quite easy to pack everything up small and send it in the post to its owner.
With everything tested and working the antenna was dispatched to my friend who soon got busy mounting it in the garden.
The loop element requires some more ties towards the box each side and some minor adjustments with the top of mast have to be made to line things up correctly but not al all bad for a permanent install. The Hoop will be part covered with surrounding plants/ Ivy over time.
A pair of 3.6mm-4.8mm wide 200mm long cable ties were used to secure the hula hoop frame firmly to the aluminium backplate through the set of four 5.0mm holes drilled into the plate earlier, These were positioned in such a way to provide additional support for the hoop frame.
An arced notch was cut into the mast at top to accommodate the top of the hoop.
I think from the initial plan , things worked out quite well.
Now on to in situ testing.
The end user is delighted with the performance for HF aeronautical monitoring.
This is an excellent all round HF receiving antenna. I was very impressed indeed with the performance during soak testing.
Here is a screenshot of the band around 4mhz to 7.5mhz. WOW !
Zooming in to the UK Volmet transmissions. Nice reception !
As I write this article (February 2023) , PCB v4.1 kits are now being distributed by the vendor M1GEO with some design improvements.
A twitter radio friend @PA9X Jean-Paul in the Netherlands has received and built a V4.1 WGL kit
Here is a tweet with close up v4.1 pcb photos , note that the pair of amplifier transistors have moved to the rear of the pcb.
Rumour: The new v4.1 boards have added voltage regulator which reduces operating volts of the amplifier PCB board to 7vdc, this would enable Li-Po battery operations.
It has been quite some time since I have added any new posts to my website blog.
Working commitments have been heavy to say the least and not much time for hobby activity.
I hope this guide helps others to build their own variant of the M1GEO Wellgood Active RX Loop Antenna.
The product is well thought out and has brilliant performance. It is very economical to purchase and superbly designed making a plethora of mounting possibilities for the radio hobbyist. Loft, Outbuilding, Indoor or Outdoor siting with wire, tube, coax, hardline element construction the choice is entirely yours.
A large loop on the ground design did cross my mind for amateur radio listening and use txr for transmit only.. maybe next time !
It is not often that a product comes along that performs this well and is relatively cheap to purchase.
Congratulations Dr George Smart M1GEO , 5 Stars All Round !
I should state at this point that I do not have any business connection with the manufacturer/designer or any supplier featured. All items shown in this article were paid for in full they were not promotional or evaluation samples. Any supplier reference list/links are mere suggestions. This article is only intended to assist others and to exchange information in the spirit of the hobby of radio.
Amplifier PCB Box IP66 BOX IP66 Schneider
Tech Info IP66 enclosure guide/downloads
Bias Tee Enclosure Project Box
Anti-Condensation (10 units) Vent Balance Valve
Tech Info Valve install-tech guide/downloads
5.5mm x 2.1mm DC socket Line socket DC
5.5mm x 2.1mm DC DC PCB mount socket
Blue LED 2mm 2mm Lighthouse LED Blue
Ring Terminals 3.2mm ring terminal
Stainless Socket Cap Screws m3 x 16 SS A2
HF Propagation Conditions