UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio 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.

Reply
 
Thread Tools
Old 30th Oct 2017, 4:43 pm   #141
Bazz4CQJ
Octode
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 1,566
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

@David, so, we are talking about using a length of coax fed through the polythene water pipe (fairly lightweight and very rigid), either 1 or 1.5m diameter. The ends of inner conductor go to the magloop amp. Are the ends of the braid connected to each other? I guess the braid could/should be earthed, but to a ground spike? With both the outer cable insulation in place, and contained in the pipe, should be quite dry.

@Symon, to start with, can you just fix the loop loosely in the shack somewhere? Chances are you'll want to play about with the amp while listening to what comes out. I intend to put it outside eventually, but have found it very interesting to have it all at arm's reach. One little finding I've made is that my amp is not optimum at 12V .

B
__________________
We know there are known unknowns. But there are unknown unknowns – ones we don't know we don't know.
Bazz4CQJ is offline   Reply With Quote
Old 30th Oct 2017, 5:10 pm   #142
G8HQP Dave
Dekatron
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 3,908
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Be careful about bringing an external earth into a room with power. This can be dangerous, and the latest RSGB advice is that it should only be done by a qualified electrician.
G8HQP Dave is offline   Reply With Quote
Old 30th Oct 2017, 5:21 pm   #143
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 9,042
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

The coax braid must not be joined end to end, that creates a shorted turn and shunts the signals you want. Ground one end and let the other end of the braid float.

'Grounding' in this case can be back to the shack via the braid of the signal coax, so no earth stake is needed at the antenna. The whole antenna and amp can be in a nice insulated box. The danger then comes if someone standing on a wet lawn opens it and can touch things grounded via the house. PME... Bah!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 10th Nov 2017, 10:08 pm   #144
Philips210
Heptode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 936
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi

At long last, I'm now in a position to give an update on my loop aerial project.

I've completed the copper pipe loop aerial which I installed on the reverse side of one of my fence panels. It measures 1.5m x 1.0m.
In the aerial junction box, the paxolin tube that fits in the copper pipe was from a damaged luminance delay line from a RBM A823 colour TV. I stripped off the damaged windings and cut the tube to about 100mm in length. It fits perfectly inside the copper tube provided that any burrs are first removed from the copper pipes. As yet, I haven't tested this aerial but made a temporary aerial from some gash 2" x 1" timber. It's a frame of dimensions 1.0m x 0.8m. I wound some 6mm² mains cable around the frame and secured it with cable ties. The whole frame was then hung over a picture on a north facing wall in the lounge.

As you may recall, I built two amplifier boards, one using the Manhattan technique and the other a PCB from David's (G4EBT) design.
After a final inspection of the boards, I powered them up minus the loop aerial and monitored the supply current. The current drawn was around 90 to 100mA which seemed fine.
First off the 'Manhattan' board fitted with RCA 2N5109s. Excellent, it's working! and what lively performance on both MW and LW. Weak stations are brought to life and one thing that's really noticeable is the lack of interference that a long wire aerial suffers from.

Next, David's PCB to which I fitted turned pin sockets to try a variety of transistors. Thanks to David for going to the trouble of designing a PCB for this project which makes it somewhat easier to construct than the Manhattan technique. I first tried the Motorola 2N5109s. Excellent again, this board is working and marginally better performance than the RCA 2N5109s. I then swapped the transistors for 2N2219As, result poor performance so these won't be suitable. I then tried David's (Radio Wrangler) 4-247s (2N3866s) supplied by Graham (StationX) and the result was even better. I'm chuffed it's all working and I'm in the process of burying the 50 Ohm coax in some conduit under the garden path. Once everything is in place I'll be able to test the amps again with the outside copper pipe loop aerial.

Incidentally, the separate indoor junction box containing the choke, capacitor and LED + limit resistor I incorporated these components in a flush mount metal electrical box buried in the wall in a bedroom. A single blanking plate was marked out and drilled to take the BNC socket, 12V power socket and LED. So it's just a case of connecting a BNC lead from the wall plate to the radio and a 12V supply to the wall plate.

My initial tests were done on a Hacker Helmsman radio which has separate external aerial sockets for (1)MW/LW and (2)SW.

In my amplifier housing, which is mounted close to the loop aerial junction box, I've decided to do away with the BNC socket as it could be tricky to avoid the ingress of water. Instead, I fitted two cable glands located at the bottom of the box. One is for the coax cable back to the house, the other for the two single wires from the copper loop aerial. I used extra flexible wire for this to give reasonable durability. All four connections are by very small screw terminal connectors for ease of access and servicing. The amplifier housing has a rubber 'O' ring in the lid to provide a good seal against moisture. I've decided not to encapsulate the board but lacquer it instead. Fingers crossed, this should stand up to the weather. I used the same type of box on a water level indicator for a water butt that I built back in 2010 and it's bone dry inside.

Anyway, I'm extremely pleased with the results so far and I'll give a further update and some pics soon. I'm hoping to test the loop aerial on a Pye P93W/U radio. If I had a working comms receiver with an S meter I could provide more technically correct results. I could try monitoring the AGC line in the Hacker or the AVC line in the Pye, that's something to consider.

Regards
Symon

Last edited by Philips210; 10th Nov 2017 at 10:21 pm. Reason: extra text
Philips210 is offline   Reply With Quote
Old 11th Nov 2017, 12:07 am   #145
Radio1950
Triode
 
Join Date: Apr 2017
Location: Brisbane, Queensland, Australia.
Posts: 20
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi everyone,
with help from David G4EBT, I recently built a Manhattan style Gary Tempest design loop amp with Central 2N5109s from Mouser USA.
The antenna is a 1.0 metre circle of 12mm OD aluminium tube.
I had hoped to trial the setup for 7.0 and 14.0 Mhz to improve a noise situation.
I measured the amp gain (with a Marconi 2022 and Icom 7600) at about 28 db at 1Mhz, and trailing off above 10 Mhz.
Works OK, especially as designed for LW and MW, but overall is not as good as a dedicated dipole for HF.
Regards to all, mike
Radio1950 is offline   Reply With Quote
Old 13th Nov 2017, 7:44 pm   #146
Philips210
Heptode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 936
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

Work continues with the amp. Today, I managed to assemble and install the conduit to take the coax cable under the pathway. A galvanised steel reinforcement pipe covers the underground horizontal run of the 20mm plastic conduit. I hope to get this finished this week so I can test the outside copper loop. As I say the results were impressive with a simple inside loop so I'm looking forward to trying out the final version.

On the amplifier housing, I decided not to make any holes though the back of the box in case the rain finds it's way in. To secure the box to the fence panel, I will place small battens around the periphery of the box. A few screw eyes will be screwed to the battens and a couple of cable ties to hold the box down. Some pics will follow when I get this completed.

Since I have two working amplifier boards then I'm going to experiment with a second loop up in the loft. At broadcast AM frequencies, I wonder how much attenuation will occur with the concrete roof tiles?

A question I'd like to ask relates to the proportions of the loop dimensions. The proposed loop is meant to be square. If a rectangular pattern is constructed would it be detrimental for the size of the width to be smaller than it's height? Is W < H worse than W > H ? Or does it not really matter too much if the aspect ratio varies either way?


Regards
Symon.
Philips210 is offline   Reply With Quote
Old 13th Nov 2017, 9:18 pm   #147
Bazz4CQJ
Octode
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 1,566
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by Radio1950 View Post
I measured the amp gain (with a Marconi 2022 and Icom 7600) at about 28 db at 1Mhz, and trailing off above 10 Mhz.
Works OK, especially as designed for LW and MW, but overall is not as good as a dedicated dipole for HF.
Regards to all, mike
I didn't make any measurements, but it was definately my impression that the loop was really good on long and medium wave, but fell off at high frequencies. How did you couple the Marconi to the loop?

I'm sure someone will come on an offer a rational explanation of why that is so. Is it an intrinsic property of loops or does it relate to the design of the particular amplifier?

B
__________________
We know there are known unknowns. But there are unknown unknowns – ones we don't know we don't know.
Bazz4CQJ is offline   Reply With Quote
Old 13th Nov 2017, 9:30 pm   #148
Radio1950
Triode
 
Join Date: Apr 2017
Location: Brisbane, Queensland, Australia.
Posts: 20
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

To feed the amp from the 2022, I just made up a small current balun on a ferrite core, and ignored impedance mismatch.
Good luck, mike
Radio1950 is offline   Reply With Quote
Old 14th Nov 2017, 9:42 pm   #149
Bazz4CQJ
Octode
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 1,566
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Yes, that's what I was thinking of too.

Spending a little time on Google, it seems that mag loops do work well on the HF bands, but for optimum performance, they need to be tuned and then have very tight bandwidths (a few kHz) so need a remote-controlled tuner (thank goodness I kept my box of stepper motors). There are lots of articles on this subject, many where the loop is being used to transmit and receive, and claims that they will compete against HF dipoles.

It seems that intolerance of large radio aerials in residential areas, in many countries, has been pushing the subject along quietly for some time.

B
__________________
We know there are known unknowns. But there are unknown unknowns – ones we don't know we don't know.

Last edited by Bazz4CQJ; 14th Nov 2017 at 9:48 pm.
Bazz4CQJ is offline   Reply With Quote
Old 14th Nov 2017, 10:11 pm   #150
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 5,175
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

For medium and longwave a single untuned copper pipe loop or square is in effect a short circuit across the antenna and earth terminals, no wonder it kills the noise, stronger signals will survive but much reduced so need amplifying...volts/amps per meter....tuned antenna is better, also loops are generally directional, more so at the lower frequencies, nailed to a fence it can only be orientated in one fixed direction, the direction of the fence...but which direction...transmitter or noise....for loop antenna a multi turn tunable loop that's rotatable for me, tuned antennas are the key, been the key since radio dot, even in 1910's W.W......Marconi etc.

Good luck whicheverways.

Lawrence.
ms660 is offline   Reply With Quote
Old 15th Nov 2017, 5:58 am   #151
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 9,042
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Nail two to fences at right angles and make a goniometer?

(I've always wondered what a non-technical person thinks a goniometer is...)

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 15th Nov 2017, 12:58 pm   #152
AC/HL
Moderator
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Idle, Bradford, West Yorkshire, UK.
Posts: 5,651
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

If they Google it they'll probably think that it's a medical diagnostic tool, you have to dig a bit deeper to unearth our understanding of the term.
__________________
Bill, BVWS member
AC/HL is offline   Reply With Quote
Old 15th Nov 2017, 3:32 pm   #153
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 7,114
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Easy, from the Greek, 'gonia' angle and 'metron' measure.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 15th Nov 2017, 3:36 pm   #154
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 5,175
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Damn it, and there's me thinking a goniometer was for measuring the transit of the bun.

Lawrence.
ms660 is offline   Reply With Quote
Old 15th Nov 2017, 4:24 pm   #155
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 7,114
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Ah, that would be a troochronos (eat time).
Back on topic (not the chocolate bar) I have always wanted a real RF goniometer and was wondering how wide band they are fed with two mag loops (with amplifiers).
Any pictures of the insides of one anybody?
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 15th Nov 2017, 7:32 pm   #156
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,147
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Isn't a goniometer the system used in most marine D/F receivers. eg the Marconi Lodestone/Lodestar jobs that I remember. Basically a crossed pair of loops and a "sense" aerial to create the Cardioid directional shape? It's all very fuzzy in the ancient memory, I may be able to dig out some old study notes but figure plenty of radio experts here who could design a DIY job on the back of the metaphorical fag packet.
Might be some online resources that would throw up some drawings/plans?
But surely for simple receiving rather than direction finding you'd do without the sense aerial and just use the omnidirectional properties of the crossed loops and use the summed signals? there'll be some glaring errors there nae doot.

Andy
bikerhifinut is offline   Reply With Quote
Old 15th Nov 2017, 7:36 pm   #157
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,147
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I seem to remember the standard DF receivers we had on board would receive very adequately broadcast transmissions right through from LW (100 plus KHz) up into the short wave bands to at least about 5Mhz, but as said before my memory isnt perfect, it was 30 years ago.....................

A
bikerhifinut is offline   Reply With Quote
Old 15th Nov 2017, 10:11 pm   #158
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 9,042
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Yep, Andy, that's a goniometer. They also get used in some colour TV test gear to vary subcarrier phase.

In the DF receiver, the static, orthogonal coils in the goniometer create a scale model in 2-dimensions of all the signals in the environment where the receiving loops are. the sense loop swung around inside the gonipmeter gives a standard 2-nulls pattern. It's equivalent to swinging a single loop around outside.

One of the benefits of having a loop is the ability to plant a null on your worst QM source.
It's worth making a goniometer. and this wayheloops inthe garden don't have to move.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 20th Nov 2017, 8:04 pm   #159
Philips210
Heptode
 
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 936
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

Just an update to my posts #144 and 146. I have now basically completed the loop aerial project installation and I'm pleased to say it is all working very well. The attached pics show the completed loop aerial.

Pic 1 shows the 15mm copper tube aerial mounted on the reverse side of a fence panel.
Pic 2 shows the completed amplifier (Manhattan version) mounted on the fence panel (the side viewed from my garden).
Pic 3 shows the amplifier box secured to the fence panel.
Pic 4 is the completed amplifier (PCB version) which will be used for further tests on a second loop aerial project for the loft.
I'm also contemplating building a third amp for the workshop when time permits that is.

I'm pleased with the results and the loop aerial is certainly unobtrusive being fixed to the back of the fence. Even the amplifier housing is conveniently hidden when the flower pots are in place.
The most notable thing with the loop is the lack of noise which is so evident with my long-wire aerial. It's been an excellent project to build and as I said would have liked to have completed it much sooner. I would definitely recommend anyone to build this project which is primarily for improved LW and MW reception though it's also useful in the lower part of the SW band as well.

Regards
Symon
Attached Thumbnails
Click image for larger version

Name:	loop aerial.jpg
Views:	27
Size:	41.6 KB
ID:	152597   Click image for larger version

Name:	loop ae amp Manhattan version.jpg
Views:	25
Size:	92.0 KB
ID:	152598   Click image for larger version

Name:	loop ae amp Manhattan version  complete.jpg
Views:	22
Size:	55.2 KB
ID:	152599   Click image for larger version

Name:	loop ae amp PCB version.jpg
Views:	26
Size:	121.0 KB
ID:	152600  

Last edited by Philips210; 20th Nov 2017 at 8:32 pm. Reason: text syntax
Philips210 is offline   Reply With Quote
Old 20th Nov 2017, 8:36 pm   #160
Bazz4CQJ
Octode
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 1,566
Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Nice looking job Symon! What receivers have you had it hooked up to?

Do you have any interest in the HF bands or does this meet all your needs?

B
__________________
We know there are known unknowns. But there are unknown unknowns – ones we don't know we don't know.
Bazz4CQJ is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 9:17 am.


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 - 2017, vBulletin Solutions, Inc.
Copyright ©2002 - 2017, Paul Stenning.