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Old 24th Jun 2017, 10:23 am   #101
bottoni
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

This one seem very promising:

http://www.pa0sim.nl/Phaser%2080%20-%2010%20meters.htm

It's been years that I want to build it, damn laziness!
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Old 28th Jun 2017, 2:59 pm   #102
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

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Originally Posted by Radio Wrangler View Post
I'm just a little bit fascinated that classic devices whose primary makers were in the US and stopped making them many years ago are still available in quantities, mostly from China.
It's something that had exercised my curiosity, too- but when one hears documentaries and news items of container-loads of the West's garbage being shipped off to China and elsewhere to be picked over by folk whose wages might be a tenth or a hundredth of ours, I wouldn't be surprised if a fair amount of new factory surplus gets picked out and sent back to us- and I doff my cap to them. Just occasionally nosing through skips on industrial estates or behind the DIY sheds, I've come across mounds of stuff that would have sold for a pretty penny- until the next year's fashion usurped it or the accountants just wanted a simple life, so the idea that it would be seized on on arrival at foreign shores by poorer folk to help purchase the next meal is entirely credible. I even once saw a news item of villagers in China using blowlamps to remove ICs from bulk PCB scrap- if there's a grapevine of what's worth looking out for and a few cents to be had for the effort, then a cottage industry will soon develop, especially in the internet/smartphone era. I wouldn't want recovered components, but I've occasionally bought "NOS" stuff from Chinese sellers that turned up quickly and appeared to be unused and unsoldered and I'm prepared to give the more mundane components the benefit of the doubt as surplus coming back to us, courtesy of those who were prepared to sift it out when we (collectively) weren't!

Obviously, anything that needs traceability is a different manner, but as David G4EBT says- to a hobbyist working away in their own time for non-critical pursuits, the auction sites can come up with amazing and eclectic possibilities.
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Old 9th Jul 2017, 7:04 pm   #103
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

Just an update on the loop amplifier. I have now completed the amplifier board and it is yet to be tested with a suitable loop aerial (to be decided). It's the first Manhattan style circuit board I've built and it's quite a fiddly process but with patience reasonable results can be achieved. I shall be building another amplifier board this time using David's PCB layout. Attached the completed board and also a blank PCB for the second board.

Regards
Symon.
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Old 9th Jul 2017, 8:41 pm   #104
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

That's a considerable effort Symon, but built for a tenth of the cost of a Wellbrook, it's worth that effort - leastways, I think so. I'm sure that when Gary spots your post he'll be well impressed. I do hope it passes its 'MOT' - 'Moment Of Truth' and that you're as impressed with its performance as I and several others have been.

Every good wish with it.
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Old 9th Jul 2017, 11:41 pm   #105
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by David G4EBT View Post
I do hope it passes its 'MOT' - 'Moment Of Truth' and that you're as impressed with its performance as I and several others have been.

Every good wish with it.
Hi David.

MOT, that's a good one, I like that! and thanks for your comments. I'm hopeful it should work as expected. The second amplifier built on your PCB will have transistor sockets so I can try out different transistors. I have some 2N3866s from Graham that I hope to test and was thinking of trying some 2N2219As as well.
I haven't decided how to construct the loop aerial, it will either be 15mm copper pipe or thick copper wire. To start with, I might try out a temporary copper wire set up later in the week.

Regards
Symon
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Old 9th Jul 2017, 11:55 pm   #106
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
I haven't decided how to construct the loop aerial, it will either be 15mm copper pipe or thick copper wire. To start with, I might try out a temporary copper wire set up later in the week.
Hi Symon. For my loops, I use cheap 'bargain shop' hula-hoops. They come in various sizes and I choose the biggest, which is about 3 feet diameter. They pull apart easily at the join and you can feed a length of coax or other thick wire through.
I house the amplifier (a simple long tailed pair similar to the PA1M design) in a plastic conduit junction box.
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Old 10th Jul 2017, 12:16 am   #107
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi Andy.

That sounds good. I think I'll give the hula hoop set up a try using thick copper wire. Thanks for the tip. I was hoping to make the loop somewhat larger and it's a pity a larger hula hoop is not easily available as a circular loop is the best shape for overall performance.

Regards
Symon.
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Old 18th Jul 2017, 6:04 pm   #108
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hello.
Gentlemen, I have spoken to my good friend and been given a stern rebuke.
He has informed me that the first stage of Mr Tempests work is freely available online and has been improved by Mr Tempest. The addition of the second stage is his work and in no way compromises what my friend has done.
Apparently many have made similar loops and many also have repaired Wellbrook loops too.
I've obviously got the wrong end of the stick and feel embarrassed by this.
Please accept my apologies.
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Old 24th Jul 2017, 7:26 pm   #109
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

I have decided to make my loop aerial using 15mm copper tube but would like to ask a few questions:

1. The dimensions of my proposed loop will be 3x4 feet. The position where I intend to fix the loop means it will have to be mounted such that the 3 feet lengths (top and bottom)) will span horizontally with the 4 feet lengths (left and right) vertically. Does it seem reasonable to build the loop with these dimensions and mounted this way? I see with David's setup his loop is 2 metres wide by 1 metre tall. My junction box will be mounted at the centre of the lower 3 foot piece of the loop.

2. So it doesn't look too obtrusive, my loop is intended to be mounted at the reverse side of one of my fence panels which is effectively on my neighbour's side. My neighbour also has a fence panel parallel to mine so the loop will be between the two fence panels. Again, does that seem OK regarding signal capture/attenuation?

3. I wonder if using 22mm or 28mm copper tube will make any improvement in the sensitivity of the loop? I looked at the price of 22mm and 28mm copper tube and nearly passed out at the price compared to when I last bought some about 7 years ago!

Regards
Symon.
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Old 24th Jul 2017, 9:07 pm   #110
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

My loop is actually 2 metres X 2 metres and is 15mm copper tube as depicted in pic 3 in my first post. I doubt that larger diameter tube would make any difference to signal strength, nor for that matter, do I think that say 2.5mm insulated copper wire would attenuate the signal strength. I think that another of Gary's friends made a larger loop using 15mm tube with no great benefit. I guess some experimentation is called for in terms of loop size and orientation.

Good luck with it Symon - I hope it performs as well as mine does.
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Old 24th Jul 2017, 11:12 pm   #111
Philips210
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi David.

Sorry for getting the size of your loop aerial wrong, I was working from memory and should have re-read the article before typing.
I'll stick to the 15mm copper tube for my loop aerial but I am also going to experiment with 6mm² copper wire in a rectangular loop and also try a circular loop using a hula hoop as Andrew2 described in post #106.
I've now built the second amplifier board using your PCB layout and have fitted individual turned pin IC sockets for the five transistors so I can try various types. I'll post some pics in due course. Thanks for the info.

Regards
Symon.
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Old 24th Jul 2017, 11:32 pm   #112
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I've used surplus / salvaged pieces of microbore heating copper pipe with very good results for receiving purposes, anything larger is probably best saved for TX use

T
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Old 9th Sep 2017, 2:04 am   #113
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Bump! It's now sufficiently like winter to resume ham radio activity here .

Looking to see what materials are in the junk box, there's a large coil of PVC pipe for underground water supply (the coil has a 'natural' diameter about 1.1m, but could be opened up) and lots of the thick coax cable used for UHF TV in the 1970's. Thought I could feed the coax through the pipe and use the braid as the loop?

This could go on top of an 8ft high wooden post which is in the middle of my garden. Rotation might be achievable using the motor taken out of a car electric window system or a small stepper motor that's collecting dust.

Has anyone made any great progress since the last post on the thread??

B
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Old 9th Sep 2017, 8:52 am   #114
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Refrigeration and aircon engineers/ installers use a softer copper pipe that is supplied in coils. 1/4", 5/16", 3/8", 1/2", 5/8" from memory. Easy to bend (sensibly). Probably a bit larger tube sizes as well, It is a long time ago to remember exactly.
Whereas plumbers tube is very hard and difficult to work with unless soldering angled joints into place.
See if any firms are local who would be willing to supply scrap at tea fund prices.
Rob
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Old 9th Sep 2017, 11:51 am   #115
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Another possible source of copper pipe would be brake pipe for cars, readily available fairly cheaply in 3/16 and 1/4 inch. Probably best to stick with the pure copper rather than the Cu/Ni alloy option?

B
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Old 10th Sep 2017, 7:39 pm   #116
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

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Rotation might be achievable using the motor taken out of a car electric window system
B
Hi.

That's a great idea for a rotator, I have a surplus unit which looks to be good for the adaption.

Progress with my loop aerial project has been hampered due to a huge amount of work committments but I would love to get it working soon and will of course report back with my findings.

Regards
Symon.
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Old 18th Sep 2017, 7:40 pm   #117
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

The prime reason for starting this thread was to enable potential constructors who are able to make PCBs, to have the option of building the amp on a PCB rather than Manhattan style. A lot of this discussion that the thread has generated has been speculation on the likely performance of a range of alternative transistors from the 2N5109 that Gary chose. To all accounts, the 2N3866 appears to be a candidate worth considering if 2N5109s aren't readily to hand, but to date, I've seen no actual results from anyone who has built a loop using alternative transistors (or indeed, using 2N5109s).

On the topic of transistors, the only feedback I've become aware of is in the link to the ‘Wellgood’ loop amp, (see post 25 of this thread). Gary has noted that part way down the page, George Smart - designer of the ‘Wellgood’ - quoted feedback he’d received from Dave, GW3WCV, who had built two of the amps designed by George. The link was quoted in post 25 of this thread and is here:

https://www.george-smart.co.uk/projects/wellgood_loop/

Dave, GW3WCV had reported thus:

Quote:

“I built them using the ZTX653 transistors you suggested, they worked great but found the frequency response dropped off dramatically above 5MHz. Swapping them for some PN2222A’s helped a lot (10dB more on 28MHz) but got 14dB more by using 2N3866 and the same result, but a bit less noise, from some 2N5109’s. Bias adjusted for 50mA through each transistor”.

End quote.

In Gary’s article in the Autumn 2016 BVWS Bulletin he went into some detail as to why he chose 2N5109s and why the collector current is set quite high. The graph on the datasheet sheet shows that the maximum frequency attainable at 50mA is 1.3GHz and at 25mA is about 1GHz, giving a gain of 40, so it seemed a good device to choose for domestic radios up to 30MHz. Gary had concerns that intermodulation distortion could arise if large signals were to swamp the amp, driving it into a non linear region so that small signals could be affected with mixing occurring. Fortunately he has a friend who lives within 30 miles of Droitwich who tested the amp on a 1 Metre loop with no sign of I.M.

This is just a short précis of the article – if anyone is that interested, and not a BVWS member, they can always buy a copy from the BVWS.

Gary Tempest contacted me recently to say that one of his amps had become intermittent, but as he’d encapsulated it, he couldn’t set about diagnosing and rectifying the fault. His suspicion is that maybe he didn’t scrape the leads of the transistors enough to remove any oxide. As he’d donated an amp to me last year, I was happy to return the favour by etching him a PCB to build another amp. He built the replacement amp and it worked, but had low gain, with noisy performance on R4 and RTE not listenable to.

In his original amps he’d used Motorola transistors, rather than the RCA ones he’d bought from Ebay to try them out. Gary has changed the front end ones from EBay RCAs to Motorola and the performance of the amp is now as per the original. He reports that R4 is now clear as a bell and RTE in Ireland pretty good from his location in Essex, with some slight background noise. I’ve attached a pic from Gary of the original Motorola transistors, and the RCA ones (low gain), that he bought off ebay. (There's been some speculation in the thread as to whether or not EBay offerings are genuine or fakes. I guess the moral is 'buy with caution and test the HFE before installing').

ON LW at my location to the west of Hull, in addition to R4, I receive good signals with minimal background noise from RTE in Ireland, and two French stations. On my 60ft end fed wire aerial the French stations are barely audible and are down in the noise. If/when others build the loop, it would be interesting to have feedback on the performance, especially if they've used alternative transistors such as 2N3866.
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Old 18th Sep 2017, 7:54 pm   #118
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I'm working on a mag loop which will use the 3866's kindly offered by Station X.

One thought that has already crossed my mind is how to evaluate the performance of the unit when completed. Testing the amp using a signal generator will require some thought. As I'm also working on moving house , I've taken down my other aerials, so I'm not going to have anything to compare it with.

It would be useful to have some "standard method" to test these units and compare results; anyone got any ideas?

B
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Old 18th Sep 2017, 7:56 pm   #119
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Does the loop have a null?

Lawrence.
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Old 19th Sep 2017, 2:39 pm   #120
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by Bazz4CQJ View Post
I'm working on a mag loop which will use the 3866's kindly offered by Station X.

One thought that has already crossed my mind is how to evaluate the performance of the unit when completed. Testing the amp using a signal generator will require some thought. As I'm also working on moving house , I've taken down my other aerials, so I'm not going to have anything to compare it with.

It would be useful to have some "standard method" to test these units and compare results; anyone got any ideas?

B
I guess that not having any aerials with which to compare the loop, you're a bit handicapped in that regard Barrie.

I evaluated the performance of the loop with my ears - simply by comparing it with a 60ft end fed wire, which is what I'd used prior to the amplified loop. There's hardly any background noise on the loop, and stations are audible that weren't heard on the end fed wire. I'm not interested in DX, so have no idea whether the loop has much of a null - I installed it for convenience on the end of my workshop, the sides of the loop facing NW/SE.

The Bulletin article quotes from an article on the directional qualities of loops in PW magazine, April '73 by S.A.Money in which he states that unless it is exactly balanced electrostatically with respect to earth it will act as a normal vertical antenna which pics up signals at equal strength from all directions in the horizontal plane. When the aerial is broadside on to the radio wave the vertical component will cancel out but the horizontal component will remain constant. This results in the loop not having a perfect null pattern'.

None of which interests me in the slightest.

As I said earlier, my aim was to simply develop a PCB alternative to the 'Manhattan style' board used by Gary. Manhattan is fine for those who don't have PCB facilities but it's a bit fiddly and widely used - often very neatly, as in Gary's example. I designed the PCB as I was so pleased with the amp that Gary gifted me that I wanted to build another for use in the house and a PCB was quicker to construct than Manhattan.

The Bulletin article ran to 11 pages in all and covered in detail the research, development, choice of transistors, method of construction and testing. I wasn't involved in any of that - I was just the fortunate recipient of one of the four amps that Gary built, and wrote an addendum to Gary's article on how the loop amp performed at my location to the West of Hull.

I don't really want to keep quoting chunks of text from the article, and in any event, anyone wishing to built it would really need the article anyway, so can read the whole thing. Suffice to say that Gary has little in the way of test gear to make measurements, but he stated in the article that his test set-up was a 1 M loop balanced on the window sill, a GEC BC3950 radio with the underside removed, a 'scope and an unmodulated 'micro transmitter' (aka 'Pantry transmitter') some distance away, the carrier of which was about 300 Metres (1 MHz).

As he felt that it was likely that some constructors would wish to locate the loop at some distance from the receiver, Gary tested it with a 30M length of 50 Ohm RG 58 feeder and 50M of RG59 75 Ohm feeder, with on loss of signal strength. He couldn't make any absolute measurements - only relative, with the AVC in the radio disabled. The article goes on to mention aspects of 'The Radio Designers' Handbook' by Langford Smith, and tests that Gary carried out with a scope and x 10 probe to ensure that there was no instability such as HF oscillations.

The amp was test at temperatures ranging from +49C to -7C with no change in performance.

To date, I know of only two amps that have so far been made using the PCB layout - one by me, the other by Gary.

Both work fine, but as always, 'ride at your own risk'!.

Hope that's of interest.
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