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Old 13th Jun 2017, 11:02 am   #21
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

An employment opportunity for all those surplus 6J6s that are kicking their heels?
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Old 13th Jun 2017, 12:27 pm   #22
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

A grounded-grid push-pull ECC88 is what crosses my mind. Maybe run from say 40V HT with zero grid bias. I haven't done any sums, so it may be too noisy.
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Old 13th Jun 2017, 4:40 pm   #23
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by D Cassidy View Post
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.
I'm not sure which circuit you are referring to that 'looks very familiar to you'.

Who are you suggesting 'should recognise the work of your very good friend?' Is his work in the public domain - if not, how would anyone know about it? Presumably you aren't suggesting that Gary Tempest has plagiarised a five-transistor circuit of 'a good friend of yours' and passed it off as his own? I'm assuming therefore that you may mean the simple 2 transistor circuit by the Dutch radio amateur PA1M, (originated by John Hawes, G4UAZ more than 30 years ago), which I referred to at post #24 of a thread entitled 'Shortwave Aerial’ I stated:

Quote:

That's the basic "Simple Active Receive Loop Antenna" design by Dutch radio amateur PA1M, which inspired Gary to develop his own design using five 2N5109 transistors.

Unquote.

http://www.vintage-radio.net/forum/s...=136486&page=2

In his Autumn 2016 Bulletin article Gary included that basic 2-transistor circuit, which he credited to PA1M and gave the link at which it could be found:

http://www.pa1m.nl/pa1m/simple-active-receive-loop/

You will see that PA1M states: "The schematic above is a look-alike from the 1984 design of John G8CXQ (G4UAZ)".

Also, at the link below, 'A Wideband Active Loop Receiving Antenna' by Des, M0AYF you will see this statement and acknowledgement:

“HF active receiving loop antenna” by John Hawes, G4UAZ (now G8CQX). Reproduced here from the "Technical Topics" column of the June 1986 edition of "RadCom" with full permission of the RSGB subject to the inclusion of the following copyright statement:

Copyright © RSGB. All rights reserved. For personal use only. Used here with permission.

http://www.qsl.net/m0ayf/active-loop...uit_diagram_is

So all in all, that 2-transistor design, now over 30 years old, has been widely circulated and credited, originally to John Hawes, G4UAZ. I've attached again the copy of the five-transistor circuit which Gary developed, which featured in the Autumn 2016 Bulletin article, along with that of PA1M which appeared on the same page and credited to PA1M. In his nine-page article, Gary fully outlined the research, development, design concepts, tests and construction of his project.

To clear up any misunderstandings that might arise, I'd appreciate clarification as to which circuit 'looks familiar to you'. Hopefully, not the one that Gary designed. You say that your friend is 'not on this board' but is elsewhere'. Neither is Gary Tempest, but he does read threads as a guest and I think he might appreciate a reassurance that no-one is 'pointing a finger at him', and come to that, so would I.
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Old 13th Jun 2017, 7:20 pm   #24
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I am hoping to build one of these antenna loop/amp systems as the high density of electronic chatter at my QTH renders MF/HF listening virtually impossible.

Is it is possible to get a better resolution image of the circuit etc. as some of the details so far posted are a little blurred.

It seems that TR3 in the emitter circuit of TR1/TR2 does not need to be an expensive HF transistor since it is only acting as a DC constant current sink of about 45/50mA. It is difficult to read the diagram but it looks like the voltage is marked 3V at the bottom end of R7/R8 which puts the voltage drop across TR3 at about 1.8V resulting in the transistor dissipating about 100mW, so it seems that almost any NPN Si will do here.

I have located a reasonably priced source of BFW16A genuine Philips transistors which are a good sub for the 2N5019, I have asked the seller for a quantity price to keep the postage element reasonable and will post this info when the reply is received in case anyone is interested in 'coming-in' on a bulk purchase.

Adrian
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Old 13th Jun 2017, 7:27 pm   #25
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

The cct of the Wellbrook is to be found on this website:

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

A genuine Wellbrook was x-rayed and then 'unpotted' and reverse-engineered. It's a standard push-pull amplifier, but there is some feedback via the input transformer.

I use a Wellbrook 1530 and can confirm that they work very well even at 17.2 KHz (the Grimeton Christmas transmissions are audible on it) and I can transmit a few watts on topband from my vertical and still get perfect reception on MW on the Wellbrook!
I've built a number of active loops using a circuit more or less identical to the simple 2-transistor design in the earlier post. I used a 3-ft dia plastic hula-hoop with a single thick wire inside as the loop element. Transistors tried were BC548, 2N2222 and 2N3866. They all worked well, but at 60mA per device the 2N3866 were deemed most suitable!
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Last edited by Andrew2; 13th Jun 2017 at 7:35 pm.
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Old 13th Jun 2017, 7:54 pm   #26
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by Philips210 View Post
I does seem the 2N5109 was used for good reason as it's decent fT figure is important
The transition frequency of many jelly bean types is way over 100 MHz!

I think this is posted as a domestic receiver antenna, not particularly for comms receivers?

I would need a lot of convincing to believe that any specialist RF types are needed for this circuit.
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Old 13th Jun 2017, 9:54 pm   #27
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by astral highway View Post
I think this is posted as a domestic receiver antenna, not particularly for comms receivers?
Surely these antennas as intended for use a bit above "domestic receiver" level?

A passionate DXer would probably have bought a house based on their ability to put up "proper" antennas, but for many of us that's hard to do. So, if you still want to listen to DX, be it on MW or SW, these antennas offer a one solution and appear to be especially good wrt electrical noise.

Given the cost of the Wellbrook, or the time and effort needed for a homebuild, I'd certainly want to be listening to something 'interesting', and probably using a receiver that was a cut above a domestic radio; the antenna is not going to give you any selectivity, except through directionality if you can turn it.

I'd certainly like to know more about why the 2N5109 has been so very popular for RF pre-amps; perhaps it is just a heritage issue?

B
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Old 13th Jun 2017, 10:34 pm   #28
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by astral highway View Post
The transition frequency of many jelly bean types is way over 100 MHz!
Hi.

The fT for the 2N5109 is actually 1200MHz (1.2GHz) so it can no doubt deliver the gain over a very wide frequency.

Regards
Symon.
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Old 13th Jun 2017, 11:03 pm   #29
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by Bazz4CQJ View Post
A passionate DXer would probably have bought a house based on their ability to put up "proper" antennas, but for many of us that's hard to do. So, if you still want to listen to DX, be it on MW or SW, these antennas offer a one solution and appear to be especially good wrt electrical noise.
I have an 80 metre dipole. Ideal for transmitting, but useless for receiving as the noise level is a constant S7 to S9, except during power cuts. I've had a Wellbrook demonstrated to me and it does a very good job of removing the noise at the expense of received signal strength.
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Old 13th Jun 2017, 11:07 pm   #30
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Does the original article give the frequency coverage of the antenna?

For the first time in many years I had a listen on my rather sick comms receiver. Top band and 80m were completely obliterated by QRM so if the loop covered these bands I would consider building one.

Al
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Old 13th Jun 2017, 11:21 pm   #31
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Al, this type of loop will work well on the bands you mention. It'll work well from below 100 KHz to 30 MHz and possibly beyond.
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Old 14th Jun 2017, 1:09 am   #32
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

This is an article I found on the web a while ago and may add something to this discussion. It refers to a Low Band (<30MHz) pre-amp described by W7IUV and using a single 2N5109 and which seems quite popular. I think it has been available as a kit in the past and there is/was an online supplier of a PCB for it which I bought quite recently.

B
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Old 14th Jun 2017, 8:09 am   #33
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

I'd just like to clarify that I started this thread not to give full blow by blow details of the ten-page article written by Gary Tempest, which featured in the Autumn 2016 issue of the BVWS Bulletin, but to say to those who had received the Bulletin, wished to build the project and had PCB making facilities, that they might want to consider that option, rather than the 'Manhattan style' board. That said, for a one-off 'Manhattan style' is probably as quick to build if not quicker, and for most constructors, would be the simplest option.

Subsequent posts have sought additional information and have queried the rationale which caused Gary to choose the 2N5109 transistor. Those queries can only be answered by quoting yet more information on the forum from the article, which is of course BVWS copyright, and as a member of the Society and occasional author of Bulletin articles myself, that was never my wish nor intention.

Back issues of BVWS Bulletins can be obtained for £4.00 each plus £1.50 post from Mike Barker, former Chairman, but I don't know if that's for non-members as well as members. Anyone who isn't a member of the Society but who is interested in the project, might wish to send a PM to Mike ('Murphymad') to arrange for a copy. They might also consider becoming a member! There aren't many days I don't have one or another Bulletin in my hand and it equates to eight pence a day - best eight penn'orth I can lay my hands on. Put another way, it works out at 12p a page on high quality glossy paper in full colour. Heck - it costs 50p a page for a colour photocopy on 80g copier paper at the local Post Office.

I'm pleased that Gary's design has attracted some interest, but for me, I think this thread has now run its distance and there is little more that I can add. Others may by all means wish to continue discuss and debate technicalities and properties of a wide range of transistors, and the merits and performance of magnetic loop amps, of which there are any number of designs out there.

I due course, it would be nice to hear some feedback from others who have built Gary's design, on their impressions of its performance.
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Old 14th Jun 2017, 8:56 am   #34
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by David G4EBT View Post
Quote:
Originally Posted by D Cassidy View Post
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.
I'm not sure which circuit you are referring to that 'looks very familiar to you'.

Who are you suggesting 'should recognise the work of your very good friend?' Is his work in the public domain - if not, how would anyone know about it? Presumably you aren't suggesting that Gary Tempest has plagiarised a five-transistor circuit of 'a good friend of yours' and passed it off as his own? I'm assuming therefore that you may mean the simple 2 transistor circuit by the Dutch radio amateur PA1M, (originated by John Hawes, G4UAZ more than 30 years ago), which I referred to at post #24 of a thread entitled 'Shortwave Aerialí I stated:

Quote:

That's the basic "Simple Active Receive Loop Antenna" design by Dutch radio amateur PA1M, which inspired Gary to develop his own design using five 2N5109 transistors.

Unquote.

http://www.vintage-radio.net/forum/s...=136486&page=2
In the absence of a response or further clarification, with the help on another forum member, I think this mystery has been solved. There can't be many in Kilmarnock with a duff Wellbrook loop 'in need of repair some years ago' but someone who is not on this forum but is active 'elsewhere' wrote this:

Quote:

8-<

Well this is not so much a home-brew item but a home-brew solution.

Way back in 2006 I bought a Wellbrook ALA1530 Loop aerial. The loop was a godsend in my noisy area, I could receive stations that it was impossible to hear on a long wire or active rod aerial (Sony AN1)

My only gripe was the output wasn't that high, a low performance radio wasn't ideal. Wellbrook though redesigned the amp later on for higher output. I got about 5 years out of the loop then it went intermittent with it cutting off if it was breezy. I discovered that the amp unit that is a plastic unit was cracked and this had compromised the loop that is a composition of alloy & ferrite, the ferrite was cracked too. The loop was then withdrawn from use.

I then discovered this circuit on the net:

8-<

End quote.

That circuit is in fact the widely circulated PA1M two-transistor design that first appeared in Technical Topics" column of the June 1986 edition of "RadCom", posted earlier in this thread, so it did not originate in Kilmarnock. Indeed, the poster himself claimed no credit for it and made it clear that 'it was not a 'homebrew item', but a 'homebrew solution' . However, given that Gary Tempest is not on this forum but is 'elsewhere', as his design unfolded, both he, the person from Kilmarnock and others discussed the design developments in an open forum.

Hopefully, this will allay any subjective and mistaken lip-jerk reactions that Gary may be passing off someone else's design as his own.

All's well that ends well.
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Old 14th Jun 2017, 9:14 am   #35
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

The BVWS article was posted up on the Golborne Vintage Radio forum, haven't done a link as there might be copyright issues?

Lawrence.
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Old 14th Jun 2017, 9:17 am   #36
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Links to The Golborne Forums are allowed here.

If the thread linked to is visible to anyone I can't see that there'd be any copyright issues.
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Old 14th Jun 2017, 9:22 am   #37
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hope this is ok:

http://golbornevintageradio.co.uk/fo...=magnetic+loop

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Old 14th Jun 2017, 9:24 am   #38
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Hi.

I'd like to ask members' views on the following points:

1. The 'tiles' used in the Manhattan style of construction are secured with cyanoacrylate adhesive (superglue). I was wondering if quick set Araldite would be suitable as it gives you a chance to position the tiles before setting? I've not used Araldite for copper to copper bonding before so that's the reason I ask this question.

2. With the bifilar wound transformer, are the two lengths of ECW twisted together prior to winding or are they just kept reasonably separate?

3. In Gary's article, he encapsulated the amplifier in a potting compound. I thought about using a good quality circuit board lacquer, any thoughts on this?

4. In the article, an earth rod is used in an early prototype. I'm not sure if it's required in the final set up, maybe not as it could be a source of noise?

5. My bungalow is located closely to the four main compass points, What wall should the loop be mounted to give the best performance?

Thanks in advance.

Regards
Symon.
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Old 14th Jun 2017, 9:30 am   #39
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Quote:
Originally Posted by astral highway View Post
Quote:
Originally Posted by Philips210 View Post
I does seem the 2N5109 was used for good reason as it's decent fT figure is important
The transition frequency of many jelly bean types is way over 100 MHz!

I think this is posted as a domestic receiver antenna, not particularly for comms receivers?

I would need a lot of convincing to believe that any specialist RF types are needed for this circuit.
OK, here's a little bit of convincing....

Ft is the frequency at which the current gain of a transistor has fallen to unity. If you want some gain from the wee beastie, then you need an Ft appreciably above your top operating frequency.

Even if power gain isn't wanted, or achieved in a circuit, you may still want current gain in order to achieve wanted input and output impedances. These circuits try to create both a moderate amount of gain and suitable impedances.

If that's not enough, these antennae are untuned and wide open to all signals in the environment, every last one. You want a transistor with high linearity at these frequencies otherwise intermodulation products of strong signals (even ones outside the tuning range of your radio can create sproggies all over the place and Murphy dictates one will be smack on top of that quiet station you want to hear. 2N5109 was designed for low intermod products and intended as a CATV amplifier device. The 2N3866 is a moderate power RF transistor, good for a QRP PA and it's pretty linear too.

You could make such an antenna work with jellybean transistors, but good RF ones should give significant advantages in several respects.

David
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Old 14th Jun 2017, 11:06 pm   #40
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Default Re: Magnetic Loop Receiving Aerial (Gary Tempest)

Well, seems like we need to identify a source of 'genuine' 2N5109's being sold at a fair price then .

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