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Old 1st Dec 2021, 8:46 pm   #21
ms660
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Default Re: Long wire AM aerial - directional?

For anyone that might be interested....LW and MW propagation.....The BBC (bearing in mind the year of publication):

https://www.bbceng.info/additions/20...ropogation.pdf

Lawrence.
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Old 1st Dec 2021, 10:18 pm   #22
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Default Re: Long wire AM aerial - directional?

Quote:
Originally Posted by ms660 View Post
For anyone that might be interested....LW and MW propagation.....The BBC (bearing in mind the year of publication):

https://www.bbceng.info/additions/20...ropogation.pdf

Lawrence.
Thanks Lawrence - you've done it again. A fascinating and absorbing document. Just what else do you have up your sleeve? That one has gone straight into my library of essential reference material.

Mike
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Old 1st Dec 2021, 10:26 pm   #23
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Default Re: Long wire AM aerial - directional?

No problem, I've probably got more links on my PC than I've got in my garden fence, I should put them in some sort of order as sometimes they can be difficult to find when I want one.

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Old 2nd Dec 2021, 8:32 am   #24
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Default Re: Long wire AM aerial - directional?

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No problem, I've probably got more links on my PC than I've got in my garden fence, I should put them in some sort of order as sometimes they can be difficult to find when I want one.

Lawrence.
Send me the BBC one covering long and medium wave receiving aerials .
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Old 2nd Dec 2021, 11:29 am   #25
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Default Re: Long wire AM aerial - directional?

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Send me the BBC one covering long and medium wave receiving aerials .
If there is one it will probably be in here:

https://www.bbceng.info/index.htm

Or here:

https://www.bbc.co.uk/rd/publications

Meanwhile I've got this one which covers the basics of receiving antennas in general (mag. page 665):

https://worldradiohistory.com/UK/Wir...ld-1926-05.pdf

Lawrence.
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Old 2nd Dec 2021, 11:44 am   #26
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Default Re: Long wire AM aerial - directional?

I've found that longwire aerials are perfectly good for LW and MW reception.

It's only when receiving amateur transmissions that interference becomes a problem and you have to use a magnetic loop.
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Old 2nd Dec 2021, 12:34 pm   #27
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Default Re: Long wire AM aerial - directional?

Here's another article, about vertical and inverted L antennas, starting on mag. page 554 with the rest of the article starting on mag. page 575:

https://worldradiohistory.com/UK/Wir...ld-1939-06.pdf

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Old 2nd Dec 2021, 12:48 pm   #28
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Default Re: Long wire AM aerial - directional?

Quote:
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I've found that longwire aerials are perfectly good for LW and MW reception.

It's only when receiving amateur transmissions that interference becomes a problem and you have to use a magnetic loop.
I have to disagree. Interference on Long and Medium waves can be very severe in some locations and at different times of the day. Many years ago I use to use an outdoor long wire aerial stretching out across the garden at about 20' high with a decent earth reception on Long, Medium and Short waves was brilliant for both local and distant stations. Now the same aerial is useless due to high levels of electronic interference many of us are being swamped with. Weaker but once audible AM stations are just completely swamped out by the higher noise levels and even the stronger local stations suffered with background hums and buzzes. I have now taken this aerial down I have also had to abandon listening on any AM radios that are only mains powered. My second aerial was a loft mounted long wire aerial which use to provide good AM reception, local and distant, but like the outdoor aerial it is now totally useless due to the high levels of local electronic interference and noise.

I now get the best AM reception, local and distant, using my portable transistor radios running on batteries and using the directional properties of there built in ferrite rod aerials for LW and MW and the telescopic rod aerial for Short Wave.
One day, if I win the lottery, I will invest in a Wellbrook loop aerial.
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Old 2nd Dec 2021, 12:53 pm   #29
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Default Re: Long wire AM aerial - directional?

Worth a read;

https://www.rnz.co.nz/listen/amhelp
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Old 2nd Dec 2021, 1:21 pm   #30
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Default Re: Long wire AM aerial - directional?

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I've found that longwire aerials are perfectly good for LW and MW reception.

It's only when receiving amateur transmissions that interference becomes a problem and you have to use a magnetic loop.
TBH, I feel the same to some extent given that the long wire is away from the sources of interference that are inside the house comprising LED lighting, wall warts, computers, TVs and so on. Yes, the internal section of the aerial is subject to this interference, but it's all a question of signal to noise ratio, and if the signal at source is strong enough, then in nett terms the reception is acceptable and certainly better than just hanging a piece of wire out of the back of the set. I'm generally please with my long wire aerial. I have looked into loops in the past (saw straight through them..) - in fact I have and use a Tecsun passive loop with some success - but in terms of much grander, powered loops I haven't gone down that route yet, and I may or may not do. There is of course the directional problem with loops.
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Old 2nd Dec 2021, 1:25 pm   #31
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Default Re: Long wire AM aerial - directional?

Quote:
Originally Posted by Hybrid tellies View Post
Quote:
Originally Posted by Station X View Post
I've found that longwire aerials are perfectly good for LW and MW reception.

It's only when receiving amateur transmissions that interference becomes a problem and you have to use a magnetic loop.
I have to disagree. Interference on Long and Medium waves can be very severe in some locations and at different times of the day. Many years ago I use to use an outdoor long wire aerial stretching out across the garden at about 20' high with a decent earth reception on Long, Medium and Short waves was brilliant for both local and distant stations. Now the same aerial is useless due to high levels of electronic interference many of us are being swamped with. Weaker but once audible AM stations are just completely swamped out by the higher noise levels and even the stronger local stations suffered with background hums and buzzes. I have now taken this aerial down I have also had to abandon listening on any AM radios that are only mains powered. My second aerial was a loft mounted long wire aerial which use to provide good AM reception, local and distant, but like the outdoor aerial it is now totally useless due to the high levels of local electronic interference and noise.

I now get the best AM reception, local and distant, using my portable transistor radios running on batteries and using the directional properties of there built in ferrite rod aerials for LW and MW and the telescopic rod aerial for Short Wave.
One day, if I win the lottery, I will invest in a Wellbrook loop aerial.
I hear what you're saying and that route is indeed a 'result'. However, for me and I suspect many other vintage radio enthusiasts, the whole point is (generally) to listen to MW and LW on a vintage set.
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Old 2nd Dec 2021, 1:36 pm   #32
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Default Re: Long wire AM aerial - directional?

[QUOTE=Hybrid tellies;1429259]
Quote:
Originally Posted by Station X View Post
One day, if I win the lottery, I will invest in a Wellbrook loop aerial.
As mentioned above Simon, you could make a clone of the Wellbrook (as discussed in previous threads) for £10-15 at most. It's based upon just two transistors and a couple of ferrite rings. The Loop can be cheap plastic water pipe (it's supplied in coiled form so already a loop) with a piece of coax running through it.

B
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Old 2nd Dec 2021, 1:40 pm   #33
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Default Re: Long wire AM aerial - directional?

"Directional properties of receiving aerials" mag page 928:

https://worldradiohistory.com/UK/Wir...ld-1925-12.pdf

Lawrence.
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Old 4th Dec 2021, 11:52 pm   #34
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Default Re: Long wire AM aerial - directional?

Quote:
Originally Posted by G6Tanuki View Post
The R4LW transmit antenna - readily visible when driving along M5 - is a "T" - there's a horizontal section supported by the two masts
Any chance of an educated guess as to the orientation?
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Old 5th Dec 2021, 1:21 am   #35
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Default Re: Long wire AM aerial - directional?

Quote:
Originally Posted by Jaded View Post
Quote:
Originally Posted by G6Tanuki View Post
The R4LW transmit antenna - readily visible when driving along M5 - is a "T" - there's a horizontal section supported by the two masts
Any chance of an educated guess as to the orientation?
From Google maps, my deeply uneducated guess would be that it's orientated roughly 170˚ – 350˚.
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Old 5th Dec 2021, 1:52 am   #36
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Default Re: Long wire AM aerial - directional?

I erected a long wire a few months ago. Quite a simple affair only about 20 foot of the ground and it has to turn through a right angle due to the boundaries of the garden, but at least 100 foot long. I get really good results during the summer months but as soon as the weather turns a little colder its performance decreases with lots of interference. I am convinced it is related a local central heating controller (or boiler). After 11.30 PM the interference disappears and normal service is resumed.
Manx radio is my station which tells me how good conditions are since I am on the very verge of their coverage.
I have tried ground rods with little effect.
Lynton
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Old 5th Dec 2021, 9:33 am   #37
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Default Re: Long wire AM aerial - directional?

Quote:
Originally Posted by Hartley118 View Post

I must confess that in my own location, I’ve practically abandoned long wire aerials and prefer a loop aerial which has two advantages:

1. It receives the magnetic component of the electromagnetic signal, which has a much lower level of nearby electrical interference than the electric component.

2. It’s directional and can be rotated to reject interference and unwanted nearby strong stations.

I use a Wellbrook loop, but others are available and you can of course also build your own. Search the forum for more information on this.

I know that this is a very indirect answer to your original question, but you’re asking about aerial directionality and a loop is the only way that you’re going to get it.

Martin
Me too. When I commissioned my RA17, I tried a long wire, and just picked up a uniform buzz from 1MHz to 30MHz and nothing to speak of by way of signal. A Wellbrook and rotator sorted that out. The best one I pulled in was Radio Australia on the 9MHz band, so good that I thought there must be a European relay. But no - they explained I was listening to a broadcast to Hong Kong, and I was either picking up a guided wave, or a transmitter side lobe. A testimony to how sensitive a sorted out RA17 can be

So I'm a great fan of magnetic loops.

Craig
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Old 5th Dec 2021, 1:25 pm   #38
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Default Re: Long wire AM aerial - directional?

Hi

Regarding the "Tee" aerial used for LW and MW broadcast transmission, If the two halves of the top part are symmetrical, the current moments are equal and opposite, so any radiation is cancelled out.

The (vertically polarised) radiation all comes from the vertical wire. The top arms add capacitance to ground which improves the efficiency. They also hold up the verical wire, which is quite handy.

If there's a bit of sag in the top, that will just add a bit to the effective height.

So it's non-directional.
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Old 5th Dec 2021, 8:44 pm   #39
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Default Re: Long wire AM aerial - directional?

Hi Craig,

Radio Australia SW has shut down all freqs.
I used it for news whilst touring in remote areas.
I am going to a remote Barrier Reef island next March, with no internet (no anything) and will use Radio New Zealand SW for news.
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Old 21st Dec 2021, 4:02 am   #40
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Default Re: Long wire AM aerial - directional?

Returning to the original question, this excerpt from “Radio and Television Engineers’ Reference Book (3rd edition, 1960) appears to provide a straightforward answer.

>>>>>>>>>>

Inverted " L " Aerials

The inverted-L aerial, Fig. 2, is probably the most. widely used of all types. It consists essentially of a horizontal length of wire, insulated at both ends and continued downwards at the end nearer the receiver, and taken as near vertically as possible to the aerial socket on the receiver. The aerial should be erected as high as possible, and may be anything from 30 to 150 ft. in length.

On medium and long waves the effective or signal responsive part of the aerial is the vertical download. The function of the horizontal part of the aerial is to add capacitive reactance to the top of the vertical section, which increases its electrical length and also raises the electrical impedance at the terminals of the aerial. Since the normal impedance of the aerial is extremely low, the losses arising from the radio-frequency resistance of the aerial conductors represent a very large proportion of the energy collected by the aerial, and the improvement effected by raising its characteristic impedance, together with the increase in effective height, is appreciable.

The top of an inverted-L aerial, while quite unresponsive to the vertically-polarized surface wave from a transmitter, is affected by downward reflected radiation from the ionosphere, and this will increase the amount of signal-fading at medium distances (50-500 miles) during the hours of darkness.

Vertical aerials are not subject to this phenomenon, and will in general be superior unless the height of the inverted L can be raised to equal that of the top of the vertical element.

The inverted-L aerial will give a satisfactory performance on short wavebands, but may exhibit resonances which reduce the strength of signals in certain directions, particularly off the ends of the horizontal section. Directivity will change with frequency, and will also depend on the total length of the aerial and on the ratio of top length to downlead; and will be very difficult to predict with accuracy.

On medium and long waves the aerial is non-directional with respect to the downlead, and it is quite immaterial which way the top section is run in relation to the direction of the transmitter.

>>>>>>>>

A scan of the full section is attached.


Cheers,
Attached Files
File Type: pdf from R&TVERB III p.21-4,5,6.pdf (346.0 KB, 30 views)
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