Aerial orientation

[stevehertz]

Thinking ahead to when/if (?!) I erect an outdoor aerial, I have a number of options re the orientation of the aerial (long wire). I'm thinking - and this is my question - is it best to have the long wire at right angles to my favoured transmitter? fundamentally, in the perfect world (which we don't live in I realise) is this true? What other considerations? My thoughts:

erect aerial as high as possible
away from trees and buildings
keep downlead away from phone downleads

[Ian - G4JQT]

Your last three points are spot on.

Regarding orientation, for all practical purposes if you are listening to anything below about 30 MHz, it won't make much difference, unless you are fortunate enough to be able to have it at least a quarter-wave long and high at the lowest frequency you want to listen to. Only then the directional properties start to be noticeable - providing there are no building, tress etc. for at least that distance all round!.

So as just a receiving aerial, orientation, bends, slope won't make much difference. Just keep it away from potential sources of interference (including down-leads of TVs) and keep the section that comes into the house as short as possible - ideally have the radio near the window-sill and aerial lead coming through a gap in the frame.

Insinuators are not really necessary, but give it a business-like appearance. This sort of thing from ebay will be more than sufficient, although any bits of plastic that are UV stable will do. The same applies to the supporting halyard.

Don't forget the earth connection. A good RF earth helps improve the effectiveness of the aerial.

Ian

[G6Tanuki]

At medium/long-wave broadcast frequencies a "long wire" antenna is not really that long in wavelength terms so it's not going to give you any real directivity (as would a multi-wavelength-long beveridge or Rhombic).

Equally, even if it's 20, 30, 40 feet up in the air a 'longwire' is going to be physically very close to the ground in wavelength terms, which will if anything make it preferentially selective to skywave [search for 'NVIS' for more explanations].

Basically, get as long a piece of wire up as you can - don't worry about orientation. It'll work just fine.

p.s. best place to get decent insulators/mounting-hardware from is an agricultural-equipment supplier: electric-fence insulators come in a range of different fittings and are a lot cheaper than those sold to the amateur-radio community!

[stevehertz]

Thanks guys, appreciated.

[Skywave]

With a 'longwire' of the inverted L type, I've always been led to believe that the vertical part should be substantially longer than the horizontal 'top', on the basis that the vertical part will be predominantly receptive to low-angle radiation and the top part adds capacity, thus lowering the aerial's natural wavelength. As for directivity, if you are after an aerial for general coverage, then the directivity isn't really that relevant, and the vertical part of that aerial will be substantially non-directive anyway.

Overall, that's my understanding - based on what I have read in authoritative sources.

Al.

[G8HQP Dave]

A lot depends on whether you are interested in groundwave (e.g. local LW/MW) or skywave (e.g. SW, distant MW) reception. Groundwave is pretty much vertically polarised, so the height of the antenna matters. The horizontal part won't pick up any signal, but it will act as a capacitive hat and so increase the signal seen by the receiver a little (by lowering imedance).

Skywave could be any polarisation, so then the horizontal part can pick up signal and should be broadside to the incoming signal. Again the higher the better (up to a limit, depending on exact angle of arrival) because the ground shorts out horizontally polarised signals.

These days, reducing interference can be much more important than increasing signal.

[stevehertz]

Thanks Al. The downlead will be from a chimney stack height - normal kinda single story house (25ft off the ground?), and the horizontal part will be around 20m, over to next door's (agreeable neighbour's) chimney. So a 'reasonable' length aerial?

[Hybrid tellies]

This is an interesting post. For a while, back I the mid 1970's, we lived in the small Cornish town of Helston. The ministry houses had largish gardens. So I ran a 60' longwire aerial from my fist floor bedroom window to a post halfway down the garden. The house was on a steep southwest facing slope and near the bottom of the hill. I got fantastic reception on all bands apart from Radio Australia on short wave. We moved to another house further up the hill and with the same aerial set up I had amazing reception on all the AM bands including R Australia. As the aerial ran north-south at both locations I think it was down to the natural screening that prevented the distant short wave signal from R Australia being received at the lower location. No directional effects were noted on the long and medium waveband as I was pulling in stations from all directions at both locations.
So its my experience that its not the aerial orientation of a long wire aerial that's important but the location of hills and tall buildings in your locality that will have some effect on short wave reception. Basically the higher the aerial better.
I seemed to remember there was an advised limit to the length of a long wire aerial feeding a domestic valved radio and think it was around 40-60' to prevent possible overloading effects. Has anyone else heard of this?

[KeithsTV]

The instruction book for my KB GR10 says the aerial "should consist of 60 - 80ft of stranded copper wire erected as far as possible from walls, trees, gutters etc and away from any source of interference such as overhead tram or trolley wires, power supply lines or any roadway carrying heavy motor traffic"

The radio was my parents and my father obviously never read the instructions as we lived next to a main road and the aerial was a few feet of wire tacked to the underside of a cupboard. Reception was good but the Droitwich transmitter was less than 10 miles away!

Keith

There used to be a limit of 100' for radio aerials, downlead and horizontal section total, it was a condition of the license. I have yet to find out if this was ever enforced and when it was no longer a requirement.

[jsbhavsar]

I currently own a National Ekco 8 band radio, containing 7 valves, model no A731 which was assembled in Mumbai downtown around 1959-60. It has a tuned RF stage that was not common those days in India or elsewhere. The set's cousin the same year was model A730 which did not have the RF stage. Both sets lacks ferrite rod antenna inside which is something to bother.

India is nowadays all about RCC buildings and apartments or tenements. I use a 1/16 thick bare copper wire around 5 meters hung between two egg insulators right on top of my building. It runs parallel to the building wall which is bad. I then have a 1/18 insulated aluminum wire around 10 meters that brings the signal from the copper wire to my radio antenna terminal. Radio earth terminal is not earthed.

My tube radio set A731 sits next to several electronic equipments in the household.
- 1 feet away from a Sony CRT TV
- 1 feet away from the TV Digital Set Top Box
- 2 feet away from Internet Broadband router
- 2 feet away from the power supply adaptors of Digital set top box, laptop and router
- 3 feet away from Philips fluorescent tube

Result:
MW and MSW bands are completely impossible to listen or receive. Noise and disturbance is excess.
SW is very very good quality; provided the electronic equipment around the radio is switched off.

India also had the indoor/outdoor mesh copper wire aerial which was a fine copper wire several hundred feet woven in a mesh. The mesh was 3 meter wide. Both side had plastic insulators. Both sides had springs. My Dad used this for his Philips India tube radio 15RB487. I used that for my National Ekco A731 but did not like it. My terrace 1/16 copper wire is little better than the mesh wire.

[stevehertz]

Nice story and nice photos. How about posting some more photos of your sets 'in situ' on my 'sets in domestic situation' post in the member introduction and news section? It would be good to see some sets as fitted in other countries?

[jsbhavsar]

stevehertz - where to upload the set pictures? I have three more pictures of the A730 set which did not carry a RF stage.

[stevehertz]

Ok,

Go to: 'member introductions and news' section..
Click on 'sets in domestic situation' post..

Take a look at the posts already there to see what it's about, then reply in the normal way and upload your photos of sets in your domestic setting.

It will be nice to see sets in a domestic setting on the other side of the world. Looking forwards to seeing the photos.

[Station X]

Originally Posted by stevehertz

Ok,

Go to: 'member introductions and news' section..
Click on 'sets in domestic situation' post.

Or just click this link:-

https://www.vintage-radio.net/forum/...d.php?t=108857

[jsbhavsar]

Done. Thanks.