UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Closed Thread
 
Thread Tools
Old 2nd Jun 2017, 5:45 pm   #1
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Magnetic Loop Receiving Aerial (Gary Tempest)

In other threads I've referred to the magnetic loop aerial designed by Gary Tempest, published in the Autumn 2016 BVWS Bulletin. I've stated that I was the lucky recipient of one of a small batch that Gary had made for evaluation prior to the article being published, and have said how impressed I've been with it, both in terms of very low background noise, and the level of amplification. (Stations that are down in the noise and inaudible on my 60ft wire aerial come in loud and clear on the loop).

Gary devised a neat 'Manhattan style' circuit board which obviates the need to etch a PCB. He used double-sided SRBP PCB sheet, and cut small 'tiles' of PCB sheet (approx 3mm square) which he stuck to the circuit board as called for, to which to solder the leads of the components. On the board layout below in pic 2, the 'tiles' are shown in grey.

I was so impressed with the performance of the aerial, which is sited on the gable end of my outdoor workshop, (the 'loop' itself consisting of a square with 2 Metre sides, with the amplifier unit sited at the centre top), that I decided to build one for use indoors. I was looking for a PCB project to try out 'dry film UV photoresist' process which was new to me, so I thought that the loop aerial would be a good project for which to design a PCB based on Gary's proven 'Manhattan style' layout.

I etched the PCB and built the amp some weeks ago, but have only just got round to testing it, which I did yesterday. Very pleased to say that it works every bit as well as the one that Gary 'gifted' to me, so I thought I'd add some pictures should anyone wish to make one. Really, for anyone who isn't into making PCBs, there's really no advantage of an etched and drilled PCB over Gary's Manhattan style' board.

In other threads I've mentioned the UV 'dry film' process which means that you don't need pre-coated UV PCB sheet or UV lacquer, so the process has much to commend it. The 'dry film' has a clear protective backing film either side of it, and to apply it to the PCB, one side is peeled off, the film is placed on the board, all air bubbles are removed and the board along with the attached film is passed through a laminator a couple of times. The artwork for the mask must be 'inverted' as the process calls for a negative image. Thus, everything that is transparent will remain on the board when exposed and developed, and anything which is opaque, will be washed off when developed, and will be etched away.

To create a negative from a positive PCB image takes only a few moments using MS 'PAINT:

Open the file in ‘PAINT’ then use the ‘Select’ option and with the mouse, select the image. Then right click on the image and a drop-down menu will appear. The bottom option on that menu is ‘invert colour’. Select that option and left click, when it will invert the colour to create the negative. Click on ‘save as’ and rename the image ‘PCB negative’ or whatever, then print off the negative mask onto acetate. Once the board has been exposed, the second protective film is removed and the board is developed and etched.

The first pic shows Gary's circuit & parts list, along with the simple 2 transistor amplified aerial from which Gary devised his own five transistor design.

The second pic is Gary's 'Manhattan' circuit board layout.

The third pic shows how the amplifier, power supply and radio connect together.

Note that up to 50 Metres of coax can be used and has been tested by Gary, without any attenuation of the signals, to send the 12V DC power to the amplifier and to feed the amplified signals back to the radio. Very useful if the loop is to be sited away from the house - perhaps at the end of a garden. As will be seen in the fourth pic, in my case, the loop was only sited 5 Metres away from the operating position. The fourth pic also shows how I used a small pill container to connect the BNC plug/socket to two wander plugs to fit the radio aerial/earth input.

The last pic shows the component side of the PCB I designed, using the same layout as Gary's.

I'll add a few more pics in another post.
Attached Thumbnails
Click image for larger version

Name:	Circuit & parts list.jpg
Views:	1482
Size:	61.4 KB
ID:	143800   Click image for larger version

Name:	LOOP ANTNNA ORIGINAL LAYOUT OF BOARD_edited-4.jpg
Views:	1015
Size:	73.4 KB
ID:	143801   Click image for larger version

Name:	Loop Amp configuration.jpg
Views:	768
Size:	28.7 KB
ID:	143802   Click image for larger version

Name:	My Loop amp setup.jpg
Views:	751
Size:	36.4 KB
ID:	143803   Click image for larger version

Name:	Mag Loop Antenna PCB Component Overlay.jpg
Views:	1034
Size:	48.2 KB
ID:	143804  

__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 2nd Jun 2017, 6:35 pm   #2
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Attached below are both positive and negative UV mask layouts that I designed for a PCB using the same proven component layout as Gary Tempest's original. The third pic is the etched and drilled PCB before de-burring and tinning. Fourth pic is the completed PCB, and the last pic shows the PCB boxed up. I tested the amplifier before attaching the heatsinks to the transistors to see if they got hot. After half an hour, the transistors had stabilised with three at 40C, one at 45C and one at 50C. The ambient room temperature was 22C at the time. They transistors were quite warm, but not hot to the touch. Nevertheless, as Gary did, I fitted heat sinks.

If the amp is to be sited outdoors it would need to be encapsulated to exclude moisture, for which Gary used Robner PX700K potting compound from Spiratronics, but as this one will be used indoors, so that's unnecessary.

These notes aren't sufficient to enable the amp to be constructed without reference to the ten-page article which featured in the Autumn BVWS Bulletin, which - in addition to constructional information - outlines the R&D that Gary put into the design. I appreciate that the thumbnail of the circuit etc in my earlier post have limitations, bit if anyone is interested in building the project, I'll be happy to forward more detailed information if they send me a PM.

The 12V 0.5A regulated, over-voltage and short circuit protected 'wall wart' power supply presently costs £7.26 INC VAT (Free delivery) from CPC/Farnell and can be found at this link:

http://cpc.farnell.com/ideal-power/2...-me-pd-mi-alte

Most of the other parts can also be found from CPC, such as the transient suppressors, plastic boxes etc.

I bought the 2N5109 NPN Motorola Transistor on ebay from a UK supplier for £2.78 for five 'buy it now' post free. To comply with forum rules I won't give the ebay link but a google search for "2N5109 NPN Transistor MOTOROLA Various Quantity" should find them.

I'm not in a position to etch PCBs for the project, but as I've said, Gary's 'Manhattan style' layout is neat and easily replicated, so has much to commend it.

Hope these notes and pics are of interest, whether or not anyone has it in mind to build one.
Attached Thumbnails
Click image for larger version

Name:	Loop Aerial DT PCB Track Side artwork_edited-2.jpg
Views:	462
Size:	51.9 KB
ID:	143810   Click image for larger version

Name:	Loop Aerial DT PCB Track Side artwork Colour inverted for negative_edited-1.jpg
Views:	367
Size:	55.5 KB
ID:	143811   Click image for larger version

Name:	PCB etched and drilled.jpg
Views:	410
Size:	63.2 KB
ID:	143816   Click image for larger version

Name:	Finished PCB.jpg
Views:	718
Size:	59.1 KB
ID:	143817   Click image for larger version

Name:	Boxed up with heatsinks.jpg
Views:	494
Size:	65.4 KB
ID:	143818  

__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 3rd Jun 2017, 6:18 pm   #3
Kevin Hoyland
Heptode
 
Join Date: Feb 2009
Location: Rotherham, South Yorkshire, UK.
Posts: 559
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

David, outstanding work. I have enjoyed reading the thread. I have been going to run coax cable from the work shop in to the home. However, seeing the magnetic loop you and Gary have made, I will have to see if I can make one for in the home.

Regards Kevin.
Kevin Hoyland is offline  
Old 5th Jun 2017, 9:04 pm   #4
G4_Pete
Hexode
 
Join Date: Feb 2014
Location: Southampton, Hampshire, UK.
Posts: 419
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

David,
The pcb brings back some memories we used a gravograph machine, the ones used for traffolyte labels and general engraving to make this style of board for a small production run in the 70's. Quick to make once you had the template set up but I do recall a degree of hand eye co-ordination was required as the cutter lift was manual not to mention people adjusting all the arm adjusters for different letter sizes for other jobs if you left the machine unattended for any time!

However thanks for sharing this as I have been looking at various loops for a while and this design now looks proven and repeatable.

Pete
G4_Pete is offline  
Old 5th Jun 2017, 10:47 pm   #5
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Thanks for reading the thread and for your comments Pete. For those who are sufficiently adept at using them (which excludes me!) small CNC millers are available for little more than £200 and hold a lot of promise for PCB production, but I'm in a rut as deep as a grave so I bimble along with UV for the few boards that I make.

For a one-off loop amp I don't think there's much benefit, if any, in making a PCB over and above Gary's Manhattan style board, which (if I've counted correctly), just requires 39 small 'tiles' of PCB sheet to be glued on the PCB laminate as anchoring points to which to solder components. The beauty of that method is that no specialist equipment is called for - just a junior hacksaw and file.
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 8th Jun 2017, 1:03 pm   #6
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

Thanks David for providing details of the PCB for this very useful project which I intend to build. As you say though, the Manhattan construction technique is most suitable and I'll probably use this method of construction. I assume the tiles are double sided copper clad board and the main board only needs to be single sided. Copper to copper bonding with cyanoacrylate. I also assume SRBP would be OK to use in lieu of fibre glass.
I also thought about using this board as an alternative http://www.ebay.co.uk/itm/1724854016...%3AMEBIDX%3AIT I am going to use this for rebuilding the Darius 625/405 line standards converter for the CCD and Clock boards.

Unless I have missed something, I cannot find the 2N5109 transistors at the price of £2.78 for five, it seems that price is for only one transistor.
I had thought about using alternatives but it seems the replacements would have to have a high transition frequency fT, a decent hFE as well as handling a fairly high current for this type of application. So it looks to be 2N5109 as there's not really an easily obtainable alternative unless anyone knows of one.

I have a long wire aerial located in the loft connected to a BALUN and also an earth rod which works quite well but is prone to noise and interference. I'm therefore looking forward to building this Loop aerial which gives excellent performance by all accounts.

Regards
Symon.
Philips210 is offline  
Old 8th Jun 2017, 3:57 pm   #7
Guest
Guest
 
Posts: n/a
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I find plain perf board (vero without copper) quite handy for simple circuits like this, you re draw it in components and solder.

Quote:
I'm therefore looking forward to building this Loop aerial which gives excellent performance by all accounts.
In a urban location loops are almost mandatory for reception.
 
Old 8th Jun 2017, 11:05 pm   #8
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by Philips210 View Post
Unless I have missed something, I cannot find the 2N5109 transistors at the price of £2.78 for five, it seems that price is for only one transistor.
I had thought about using alternatives but it seems the replacements would have to have a high transition frequency fT, a decent hFE as well as handling a fairly high current for this type of application. So it looks to be 2N5109 as there's not really an easily obtainable alternative unless anyone knows of one.
I bought mine in mid 2016 - the best up-to-date offering I can find now is five for £11.99 plus £1.00 P&P from a UK supplier, at this link:

http://www.ebay.co.uk/itm/5x-2N5109-...item35d312c897

I guess that 2n3866 might be a suitable alternative from the same supplier at £6.49 + £1.00 (almost gone):

http://www.ebay.co.uk/itm/5x-2N3866-...3D231174490263

Gary states that he used double side FR4 laminate, cleaned it with wire wool and thinners before super-gluing the pads or as Gary calls them 'tiles'.

Hope that helps a bit.

Good luck with it.
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 9th Jun 2017, 9:45 am   #9
trh01uk
Octode
 
trh01uk's Avatar
 
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,648
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

David,

not being a member of the BVWS I haven't seen the original article, and you don't say in what way the performance impressed you. I presume also that being "AM" - this is long wave and medium wave bands - with perhaps some coverage of short waves as well - the circuit looks like it is broadband.

I have also found loops work well - at least for receiving - particularly in noisy conditions. And these days that's just about everywhere except for those few souls living in isolated houses well away from all other civilisation, farms, etc. Generally its useful to be able to rotate the loop, if there is a predominant noise source nearby - so that it can be steered into the loop's null, while hopefully still picking up the wanted signal.

Much of the amateur radio comment on loops has concentrated on transmitting - and that's a whole different ballgame of course, with the question of efficiency arising. I've found the loop most useful for receiving - and for those who want to transmit, just have a separate antenna for the purpose.


Richard
trh01uk is offline  
Old 9th Jun 2017, 12:11 pm   #10
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Thanks again David for your reply and the links.

Regards
Symon.
Philips210 is offline  
Old 9th Jun 2017, 3:00 pm   #11
David G4EBT
Dekatron
 
David G4EBT's Avatar
 
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by trh01uk View Post
Not being a member of the BVWS I haven't seen the original article, and you don't say in what way the performance impressed you. I presume also that being "AM" - this is long wave and medium wave bands - with perhaps some coverage of short waves as well - the circuit looks like it is broadband.
I wrote a two-page evaluation at the end of Gary's article in which I compared the performance of the loop, (mounted on the end of my wooden workshop), with a 60ft wire aerial which I had used up to that point. The most noticeable thing is the almost complete absence of background noise, and the considerable increase in signal strength of stations on the loop. Taken together, these factors meant that stations which were inaudible and down in the noise, came in at good signal strength with little background noise. (I didn't carry out and experiments to see to what extent, if any, the aerial was directional). My 'loop' is a square of 15mm copper plumbing pipe with 2 Metre sides. No calculations - just a convenient shape to fit on the outside of the gable end of my workshop.

In all, Gary made four amplifiers, and in addition to his own and mine, the users of the other two reporting similar results to mine.
__________________
David.
BVWS Member.
G-QRP Club member 1339.
David G4EBT is offline  
Old 10th Jun 2017, 5:10 pm   #12
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

Isn't it strange that after recently discussing the availability and price of the 2N5109 transistors, and a new search on ebay, lo and behold, reveals a number of suppliers all at very reasonable cost? These are of course from China and I can't help wondering if they are the real thing made by Motorola. It's a bit of a gamble purchasing cheap transistors what with all the hype about fake components. The trouble is, even the medium/high price parts might not be genuine. It's a minefield so who can you trust?

Regards
Symon.
Philips210 is offline  
Old 10th Jun 2017, 6:00 pm   #13
Guest
Guest
 
Posts: n/a
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Given the much better transistors made today I would think anything with the power capacity of the 2N5109 will work very well.
 
Old 10th Jun 2017, 8:14 pm   #14
AC/HL
Dekatron
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Googling 2N5109 leads quickly to this page: http://www.pa1m.nl/pa1m/simple-active-receive-loop/, which gives BFW16A as an alternative. Whether or not that is riskier I don't know.
AC/HL is online now  
Old 10th Jun 2017, 9:37 pm   #15
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,923
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

For what it's worth, I bought a single 5109 on line a while ago which was marked as RCA, and so I was optimistic it would be good. However, when tested on my two multimeter transistor testers, both suggested that it's gain was pretty much at the bottom of the spec. As it's intended for an RF pre-amp (not yet built), I thought that was disappointing .

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is offline  
Old 11th Jun 2017, 3:00 pm   #16
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Thanks Bill for the link.

Regards
Symon.
Philips210 is offline  
Old 11th Jun 2017, 3:12 pm   #17
Al (astral highway)
Dekatron
 
Al (astral highway)'s Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

To extend MM's point , 5109's look pretty and 'proper vintage' because of their metal cases, but there are plenty of jelly bean types for far cheaper that will work just fine.

ZTX451, just as one example, is very comfortable at a far higher current and with no heatsink.
__________________
Al
Al (astral highway) is offline  
Old 12th Jun 2017, 10:35 pm   #18
D Cassidy
Retired Dormant Member
 
D Cassidy's Avatar
 
Join Date: Oct 2015
Location: Fenwick, Glasgow, UK.
Posts: 127
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hello.
That circuit seems very familiar to me. A very good friend of mine repaired his wellbrook loop with a virtually identical set up some years ago. He lives in Kilmarnock and I sincerely hope that his work has been recognised. He is not on this board but is elsewhere.
D Cassidy is offline  
Old 12th Jun 2017, 11:21 pm   #19
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,799
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

There was a very large number of 2N3866 transistors (many thousands) distributed for free amongst the QRP groups of the world. They are similar enough to the 2N5109. TO-5, they carry the Motorola 'Batwing' markings and '4-247' in case anyone comes across some. They were going to go for scrap metal otherwise.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 13th Jun 2017, 9:28 am   #20
Philips210
Nonode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

I does seem the 2N5109 was used for good reason as it's decent fT figure is important not to mention a good hFE and also a a good noise figure. The available gain from these devices comes into play when operated with a moderate collector current. If operated at low IC then it cannot deliver the expected gain. As far as I understand, the gain of a transistor is at a maximum for a specific collector current only.
I've read a 2N2219A will be a suitable replacement but it's noise figure is inferior to the 2N5109.
I have just started building the circuit and have so far cut out the 'tiles' and will make the circuit board later.

Regards
Symon.
Philips210 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 3:47 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.