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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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1st Dec 2021, 8:46 pm | #21 |
Dekatron
Join Date: Apr 2011
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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. |
1st Dec 2021, 10:18 pm | #22 | |
Octode
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Re: Long wire AM aerial - directional?
Quote:
Mike |
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1st Dec 2021, 10:26 pm | #23 |
Dekatron
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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.
Lawrence. |
2nd Dec 2021, 8:32 am | #24 |
Dekatron
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Re: Long wire AM aerial - directional?
Send me the BBC one covering long and medium wave receiving aerials .
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2nd Dec 2021, 11:29 am | #25 | |
Dekatron
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Re: Long wire AM aerial - directional?
Quote:
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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2nd Dec 2021, 11:44 am | #26 |
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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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2nd Dec 2021, 12:34 pm | #27 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
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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 Lawrence. |
2nd Dec 2021, 12:48 pm | #28 | |
Nonode
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Re: Long wire AM aerial - directional?
Quote:
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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2nd Dec 2021, 12:53 pm | #29 |
Nonode
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Re: Long wire AM aerial - directional?
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2nd Dec 2021, 1:21 pm | #30 |
Dekatron
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Re: Long wire AM aerial - directional?
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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2nd Dec 2021, 1:25 pm | #31 | ||
Dekatron
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Re: Long wire AM aerial - directional?
Quote:
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2nd Dec 2021, 1:36 pm | #32 | |
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Re: Long wire AM aerial - directional?
[QUOTE=Hybrid tellies;1429259]
Quote:
B
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2nd Dec 2021, 1:40 pm | #33 |
Dekatron
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Re: Long wire AM aerial - directional?
"Directional properties of receiving aerials" mag page 928:
https://worldradiohistory.com/UK/Wir...ld-1925-12.pdf Lawrence. |
4th Dec 2021, 11:52 pm | #34 |
Triode
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Re: Long wire AM aerial - directional?
Any chance of an educated guess as to the orientation?
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5th Dec 2021, 1:21 am | #35 |
Octode
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Re: Long wire AM aerial - directional?
From Google maps, my deeply uneducated guess would be that it's orientated roughly 170˚ – 350˚.
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5th Dec 2021, 1:52 am | #36 |
Hexode
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Location: Greater Manchester
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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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5th Dec 2021, 9:33 am | #37 | |
Dekatron
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Re: Long wire AM aerial - directional?
Quote:
So I'm a great fan of magnetic loops. Craig
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5th Dec 2021, 1:25 pm | #38 |
Heptode
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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. |
5th Dec 2021, 8:44 pm | #39 |
Hexode
Join Date: Apr 2017
Location: Buderim, Queensland, Australia.
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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. |
21st Dec 2021, 4:02 am | #40 |
Nonode
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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, |