Magnetic Loop Aerial - tube or wire and layout for Rx only? - UK Vintage Radio Repair and Restoration Discussion Forum

6SN7WGTB · 29th May 2025, 9:43 am

I'm considering making up the BVWS/Gary Tempest magnetic loop aerial amplifier.

I have some questions:
1. Given it's receive only, can I use simply wire not tube? Does the gauge matter particularly, aside for mechanical robustness?
2. I happen to have a very convenient mounting platform (a wooden pergola thing) but/and this would give me a roughly rectangular aerial which would be quite large - i.e. about 3.5m wide and about 2.5m tall. The bottom horizontal would be just above ground level. Will this be suitable?
3. Not really a Q, but a statement - the pergola is about 20m away from the house (good thing I hope) and therefore will use coax and power injector per original design.
4. Doe sit matter which 'leg' the amplifier gubbins goes in? It would be much easier for me to put the amp in one of the vertical legs.

Comments most welcome!

I'm planning an SMD design to fit in a Whiska box at the chosen place in the loop.

Radio Wrangler · 29th May 2025, 10:29 am

1) You can use wire. Tube gets used for the convenience of it being self supporting, convenient if you want to rotate it to peak signals or null noises.

2) That size shouldn't be a problem. Signal pick-up is proportional to enclosed loop area.

3) Use a nice ferrite bead around the coax at each end to stop any common-mode stuff picked up on the feeder getting into the stuff at the ends. Maybe a few turns on a toroid.

4) any leg.

David

6SN7WGTB · 29th May 2025, 11:20 am

Brilliant, thanks David.

Bazz4CQJ · 29th May 2025, 12:55 pm

I think Gary has published 2 designs, both in BVWS? Are the schematics available by any other route?

B

6SN7WGTB · 29th May 2025, 1:36 pm

Quote:

Originally Posted by Bazz4CQJ

I think Gary has published 2 designs, both in BVWS? Are the schematics available by any other route?

B

It would appear this thread on our forum has the details:

https://www.vintage-radio.net/forum/showthread.php?t=156263

Bazz4CQJ · 29th May 2025, 4:11 pm

I may be wrong, but I'm not sure that Gary's second design appears there

. I've built Gary's first design and the Wellgood.

I've built two loops, both being based on 1 inch plastic water pipe (blue). I think the first used old style thick coax (passed down inside the pipe) to provide the screen and the active loop. The second used copper brake pipe as the screen with insulated stranded wire inside that as the active element.

B

David G4EBT · 29th May 2025, 4:40 pm

A few points that might help:

As to 'layout for receive only' - the magnetic loop is for receive only.

As to 'wire rather than tube', that's fine.

The Welbrook Loop was 1 Metre diameter, but it's a broadband aerial, so the diameter isn't critical.

When I built my Gary Tempest 'Wellgood' Clone' one, to do the initial tests I just used a loop of insulated wire about 2 Metres square draped over a curtain rail in my 'hobbies room' and it worked fine. (It could easily have stayed there, hidden behind the curtains). As it was going to be (is) sited in my garage loft I made a 1 Metre circle of 15mm copper tube, but it could just as well have been square, octagonal or whatever, using 15mm end-fed copper tube fittings. It only needs to be made of pipe for durability if it's to be sited outdoors.

Some people have used kids' hoola-hoops with wire inserted in them.

Garry built his using 'Manhattan' style with little pads of PCB glued to PCB laminate. I mimicked that layout and designed a PCB with straight lines which could be made by sticking which 'Fablon' onto PCB laminate with the paper layout stuck to that, and the shapes cut with a craft knife, with the waste between the 'lands' removed. The PCB could then be etched and drilled. No need for a UV mask, a UV exposure box or developer.

For those who have had success with 'iron on' PCBs the layout could be printed off and ironed on.

Gary's original BVWS Bulletin article (Volume 41, Number 3, Autumn 2016) can be viewed or downloaded at this link, whether a BVWS member or not:

https://www.bvws.org.uk/publications/bulletins.php/volume41number3

The one that Gary gifted to me back in 2016 is still in use in my outdoor workshop.
I used a 2 Metre square of 15mm tube for the loop, fixed on the outside gable end of the workshop.

Hope that might help a bit.

Radio Wrangler · 29th May 2025, 7:10 pm

I still have some of those 2N3866s left if anyone needs a few

David

David G4EBT · 29th May 2025, 7:32 pm

Quote:

Originally Posted by Radio Wrangler

I still have some of those 2N3866s left if anyone needs a few

David

None finer!

(A grateful recipient

).

29th May 2025, 9:43 am	#1
6SN7WGTB Heptode Join Date: Apr 2021 Location: Crawley, West Sussex, UK. Posts: 511	Magnetic Loop Aerial - tube or wire and layout for Rx only? I'm considering making up the BVWS/Gary Tempest magnetic loop aerial amplifier. I have some questions: 1. Given it's receive only, can I use simply wire not tube? Does the gauge matter particularly, aside for mechanical robustness? 2. I happen to have a very convenient mounting platform (a wooden pergola thing) but/and this would give me a roughly rectangular aerial which would be quite large - i.e. about 3.5m wide and about 2.5m tall. The bottom horizontal would be just above ground level. Will this be suitable? 3. Not really a Q, but a statement - the pergola is about 20m away from the house (good thing I hope) and therefore will use coax and power injector per original design. 4. Doe sit matter which 'leg' the amplifier gubbins goes in? It would be much easier for me to put the amp in one of the vertical legs. Comments most welcome! I'm planning an SMD design to fit in a Whiska box at the chosen place in the loop. __________________ Richard \| BVWS & RSGB member \|

29th May 2025, 10:29 am	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 24,748	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? 1) You can use wire. Tube gets used for the convenience of it being self supporting, convenient if you want to rotate it to peak signals or null noises. 2) That size shouldn't be a problem. Signal pick-up is proportional to enclosed loop area. 3) Use a nice ferrite bead around the coax at each end to stop any common-mode stuff picked up on the feeder getting into the stuff at the ends. Maybe a few turns on a toroid. 4) any leg. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

29th May 2025, 11:20 am	#3
6SN7WGTB Heptode Join Date: Apr 2021 Location: Crawley, West Sussex, UK. Posts: 511	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? Brilliant, thanks David. __________________ Richard \| BVWS & RSGB member \|

29th May 2025, 12:55 pm	#4
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 5,373	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? I think Gary has published 2 designs, both in BVWS? Are the schematics available by any other route? B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

29th May 2025, 4:11 pm	#6
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 5,373	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? I may be wrong, but I'm not sure that Gary's second design appears there . I've built Gary's first design and the Wellgood. I've built two loops, both being based on 1 inch plastic water pipe (blue). I think the first used old style thick coax (passed down inside the pipe) to provide the screen and the active loop. The second used copper brake pipe as the screen with insulated stranded wire inside that as the active element. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch. Last edited by Bazz4CQJ; 29th May 2025 at 4:21 pm.

29th May 2025, 4:40 pm	#7
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 6,176	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? A few points that might help: As to 'layout for receive only' - the magnetic loop is for receive only. As to 'wire rather than tube', that's fine. The Welbrook Loop was 1 Metre diameter, but it's a broadband aerial, so the diameter isn't critical. When I built my Gary Tempest 'Wellgood' Clone' one, to do the initial tests I just used a loop of insulated wire about 2 Metres square draped over a curtain rail in my 'hobbies room' and it worked fine. (It could easily have stayed there, hidden behind the curtains). As it was going to be (is) sited in my garage loft I made a 1 Metre circle of 15mm copper tube, but it could just as well have been square, octagonal or whatever, using 15mm end-fed copper tube fittings. It only needs to be made of pipe for durability if it's to be sited outdoors. Some people have used kids' hoola-hoops with wire inserted in them. Garry built his using 'Manhattan' style with little pads of PCB glued to PCB laminate. I mimicked that layout and designed a PCB with straight lines which could be made by sticking which 'Fablon' onto PCB laminate with the paper layout stuck to that, and the shapes cut with a craft knife, with the waste between the 'lands' removed. The PCB could then be etched and drilled. No need for a UV mask, a UV exposure box or developer. For those who have had success with 'iron on' PCBs the layout could be printed off and ironed on. Gary's original BVWS Bulletin article (Volume 41, Number 3, Autumn 2016) can be viewed or downloaded at this link, whether a BVWS member or not: https://www.bvws.org.uk/publications/bulletins.php/volume41number3 The one that Gary gifted to me back in 2016 is still in use in my outdoor workshop. I used a 2 Metre square of 15mm tube for the loop, fixed on the outside gable end of the workshop. Hope that might help a bit. __________________ David. BVWS Member. G-QRP Club member 1339.

29th May 2025, 7:10 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 24,748	Re: Magnetic Loop Aerial - tube or wire and layout for Rx only? I still have some of those 2N3866s left if anyone needs a few David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done