Broadcast/Shortwave Aerials? Confusion... - Page 1
Forum section: electronics / general

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 10, 2020, 01:05:04 pm
content: I'm getting back into rebuilding a lot of vintage valve radios, and that's not the problem.However, although IDOresearch it, I get lots of conflicting info about general/basic Aerial use!Most of my old vintage receivers have an Aerial & Ground terminal, and ONE of them even hasadditional terminals for a 'Di-Pole' !!I'm not into the Ham bands as such, but mainly the Broadcast band, various SW bands, & LW.A FEW of them, (very few!), have/use internal ferrite rods/coils in the initial aerial circuitry, whichare used in just 'some' bands, and also require physical orientation of the 'radio' to work best.Can someone guide me to (or explain!) what is basically required in a simplistic manner, to buildan aerial system(s) in a typical 'country' environment, say 180-kms from a major city?? And doesthe ubiquitous 'Long-Wire' generally suffice?? or are design considerations preferred

author: babysitter
author_rank: Frequent Contributor
timestamp: July 10, 2020, 02:14:50 pm
content: Hook up the wire you easily find, at the place that you have, up and behind the radio set. Connect earth if available, or any bigger metal structure.

author: rdl
author_rank: Super Contributor
timestamp: July 10, 2020, 07:29:41 pm
content: Ground for a radio antenna really means ground, something like copper pipe hammered several feet into the ground. For the antenna, use the longest wire possible unless you have room for an actual antenna which would be sized according to the signals you want to receive.General suggestion here: anybody with the slightest interest in radio should get a copy of the ARRL Handbook. It doesn't need to be the latest edition, a cheap, used copy is fine.

author: vwestlife
author_rank: Regular Contributor
timestamp: July 10, 2020, 07:45:08 pm
content: The internal (or sometimes external) coil antenna is for the mediumwave (AM) and longwave bands, approx. 150 to 2000 kHz, and is directional -- rotate it (or the entire radio, if it's internal) for best reception. If your radio has a whip antenna, it does not need to be extended when listening to LW or MW/AM -- in fact, having it extended might actually cause interference on a cheaper single-conversion receiver. An external antenna for these bands should be as long as possible and ideally located outdoors, along with a good earth ground connection, if your radio has a terminal for it.Shortwave (2 - 30 MHz) uses the radio's whip antenna, if it has one, or an external antenna, usually around 20 to 50 feet in length.A dipole antenna connection would be for FM (88-108 MHz). If you don't have a dipole, just connect a single piece of wire to one of the terminals, usually around 3 to 4 feet in length.

author: VK3DRB
author_rank: Super Contributor
timestamp: July 11, 2020, 04:35:07 am
content: If you are out in the country and want to get DX stations (distance), consider building an external loop antenna. By turning the loop, these are quite directional and you can null stations in certain directions and get extra gain in other directions. They need not be large. I built one about 30 years ago using several turns of wire on a cross frame and added a tuning capacitor to from an LC circuit. The length of each side was about 1.5m. It worked a treat. I worked a lot of AM DX and could pick up AM radio station 2CA in Canberra from as far away as Wangaratta night or day via ground path.Alternatively, consider one of these:www.amradioantennas.com. They work exceedingly well. They work by inductive coupling to your radio antenna. You can have a crap antenna in your radio, but this is a simple and easy-to-install game changer.

author: Kerlin
author_rank: Regular Contributor
timestamp: July 13, 2020, 01:12:40 am
content: Dont want to be a troll but I have to tell you this, that saying you are not into ham radio or anything like that does not mean you can skip the theory, and just saying "But I just want improve the use of my radio" also will not work.The rules of nature are king and we can only obey them.In fact despite all the stuff you read on forums you MUST have BOTH the theory and practical knowledge, only after you completely have these can you bend the rules a to suit yourself.Same goes for all of Electronics.Despite its legendary status the ARRL antenna handbook, although necessary is not that helpful for what you are looking for.Learning such things is easier than ever.I paid thousands of dollars for books covering this topic and spent ten of years at university to find the information you can now get on the internet for free.You just need the discipline to do it, there is NO other way.Having said that here a few suggestions.1- An impedance matching device such as a 4:1 up to a 64:1 device is is very useful.Most probably a 9:1 is as far as you need to go.To use it you need to have some idea of the impedance of your antenna and the input impedance of your radio.If you don't know these then you can experiment by measuring it or simply guessing, a guess to start with might be that your long wire antenna on the broadcast band is thousands of ohms and your radio is some where from a few hundred ohms to a thousand ohms.To correctly make a matching transformer you will need to study balun and transformer types, Rutherov and Guallena.You will need to study ferrite and powdered iron types and their uses, in particular which type is suitable for the broadcast band.Also look at if you would use a rod or toroid type.2- You might look at putting a band pass filter in between you radio and the antenna.the reason is if a strong signal is getting into your radio, and it can easily be an FM station or even TV station, it will reduce the sensitivity of your radio.These other unwanted signals don't even need to be strong.Find out what "desensing" is.3. Desensing can also be be caused by another AM station.Find out what an adjacent station trap is, how to make one, and how to use one.They are very useful.They are basically nothing more than a series tuned circuit.4- Consider putting a solid state, or hollow state if you must, RF preamplifier between the antenna and radio.But be careful not to overload the radio this would probably mean the amplifier has a gain control so you can stop overloading (google it).Also the amplifier must not produce crossmod.5- There is some debate on whether an antenna tuner is useful, I have found not.There are reasons for that.Lets not start that argument here, you will find plenty of them on the net.There are heaps of other things that can be done.There are many people who use the simplest of receivers, crystal sets, to receive overseas broadcast stations and successfully too!!I know some and have done it myself.I totally guarantee that I could do things with that radio that would stun you, no not because I think I am smart ( that never helps), but because I have put decades of work into learning the practice and theory of this matter.As I have said, again there is no other way, the rules of nature are king.That is until we can enter the realms of Super Nature were we rewrite the rules.

author: Kerlin
author_rank: Regular Contributor
timestamp: July 13, 2020, 01:38:12 am
content: Check that post again as I have made a few additions.

author: cdev
author_rank: Super Contributor
timestamp: July 13, 2020, 01:41:45 am
content: Read up on lightning protection issues if you get lightning storms a lot. But generally you want to get a wire antenna up as high as you can and get as good a ground as possible. .Quote from: babysitter on July 10, 2020, 02:14:50 pm

author: Kerlin
author_rank: Regular Contributor
timestamp: July 13, 2020, 01:46:15 am
content: May help for safety, but it should already have an earth and a low resistance path to it from the antenna.But not so critical for the radio as its a valve receiver.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 17, 2020, 11:42:20 am
content: Quote from: Kerlin on July 13, 2020, 01:12:40 amHi there 'Kerlin'. Thank you (and the others here!) for the details supplied above byall.I am a bit taken aback/confused with your initial statements though?? (I'm trying to structure my thoughts here).Firstly, I'm not only 'getting-on-a-bit', but also have a greatly limited 'future' medically. Believe me, 'Google' is myfriend, and there is not too much one can't find if you know where/how to look these days. I LOVE researchingthings, but I don't have the ability now to go through years of studies in particular fields any more.I guess it's like the 'Medical' field. SomeoneMAYwant/need/like to understand say 'Orthopedics', or 'Immunology',but after many years in such fields, they know little in regards to say 'Brain-Surgery' or 'Heart-Transplants'So my 'question' was quite generic without trying to get too technical, after reading many 'thoughts' about it.When i said things like... "I'm not into HAM radio"...AllI really meant, is that I'm not dealing with 'Transmitters'where obviously special aerial designs are specifically important in that regard. Although I would not ever come closeto understanding what some people (and you) understand, all I meant is things like...."Should one use a coax out to an external aerial", or "Should I bother with tuned aerial lengths for MW/SW bands",or "Is it beneficial using a directional loop antenna", or "just use a Long-Wire for basic needs"...That was generally explained, and I'm thankful. Am not trying to get too deep!

author: Kerlin
author_rank: Regular Contributor
timestamp: July 21, 2020, 07:59:02 am
content: That's it he has done it.Notice how I predict he will just make an excuse, and he does, multiple ones.But it went further than that he skipped over all my suggestions and ignored them.I wasted my time answering.That's it he has done it, from now on I must resist the temptation to help people, just sit on the side.It happens too often on all forums.

author: tkamiya
author_rank: Super Contributor
timestamp: July 22, 2020, 05:00:44 am
content: I'm not sure if I can achieve a balance between being simplistic and theory, but here goes....Antennas can be divided into two categories. Resonant type and non resonant types. Dipoles are basis of resonant type and random wire, ie. long wire antennas are non resonant types. They both work and work well.Resonant types are cut for a certain frequency. Length of element is based on half a wave length and for exact formula, you can easily look up various literature. This is a very efficient form of antenna but has one major draw back. It's good for one frequency, and odd multiple there of. So you will need multiple of these to cover various HF bands.Non-resonant types are often just a random length of wire stretched as long and as high as possible. It works well on all frequencies if you have a proper matching network, and a suitable and good grounding system. For listening purpose, just a wire as long as possible will perform respectably. Basic rule applies here. Longer, higher, away from noise sources, and do it safely. That's it. This is the type I have. I also have a very basic grounding system. Not very efficient compared to resonant types, but most broadcasters are in Multi-Killowatt ranges on HF bands. Good enough is, really good enough.You can get infinitely complex from here, but I don't think it applies here. I don't recommend over-thinking this at beginning. Soon enough, they will catch up to you.

author: tautech
author_rank: Super Contributor
timestamp: July 22, 2020, 10:07:58 am
content: It doesn't need to be anything more than a long wire hung between the house/shack and a tree with insulators at each end and end fed.....with the obligatory lightening arrestor and ground if leaving gear connected or listening in shitty weather.Dad listened to SW from all over the world in the 40's and 50's from little old NZ mind you many were directional SW broadcasts towards downunder.In my teens I played a bit with SW too and got contacts from OZ, US and EU with just a rudimentary length of wire and cheap SW transistor radios.Dads stuff was all home built often with handmade coils and all valve based. Well remember him teaching how to make a wave trap wound on a toilet roll tube.There's certainly no need to overthink it for it to just work.

author: vk6zgo
author_rank: Super Contributor
timestamp: July 22, 2020, 12:40:28 pm
content: Quote from: tautech on July 22, 2020, 10:07:58 amExactly!Old domestic valve radios were quite sensitive, & had relatively high impedance inputs.Many will give reasonable results with quite abysmal antennas.When I was a kid, we lived "in the bush" (not that far from Perth WA, but we didn't have Mains power).Our home radio was a valve portable, & after local broadcast hours we could hear a lot of distant stations on MW, usually from the Eastern States, but on several occasions, the USA.We had a decent end fed outside antenna attached to a tree, which then sloped down into the house, where it plugged into the portable's "external aerial" socket.An earth lead was provided to a quite small stake in the garden, but on occasion, the earth lead fell out with no obvious change.My brother used the same antenna for his regenerative receiver, which used battery valves.He listened to a lot of HF stuff on that antenna.When "Z" call amateurs finally got HF privileges, I picked up a Yaesu FT301 transceiver, brought it home, grabbed some random wire, chucked it out the back, connected up the radio & had a listen to the 20m band.The radio was seemingly "deaf as a post", & I was devastated, but went ahead with putting up a 20m dipole.Now the band was "jumping with signals"..Radios with low impedance inputs don't play well with random length anennas without any matching circuit.Scungy old mantel sets work well with such antennas.

author: GlennSprigg
author_rank: Super Contributor
timestamp: July 22, 2020, 01:45:38 pm
content: Quote from: Kerlin on July 21, 2020, 07:59:02 amReally... what is your problemKerlinFirstly, I DID take notice of the TECHNICAL info you spoke of, & I thankedyou/othersfor it!!In fact, I copy/pastedALLthe tech info from everyone, includingyou, and saved it all in a file.You say you 'predicted' that i would & did make multiple excuses...What drugs are you on??...I simply re-explained what I was trying to find out, in a simplistic way, & considering my limited timeon this good Earth totake it all in!! I'm sorry I don't come up to your 'standard'...I wasted my time answering.That's it he has done it, from now on I must resist the temptation to help people, just sit on the side.It happens too often on all forums.Sigh...EVERYONEelse here spoke in a friendly manner, and were respectful. Other than yourtechnical words, and ESPECIALLY in your last 'reply'... you seem to have aMASSIVEchip on your shoulder!If that happens "all too often" on "all forums", what may that suggest toYOU!!My life isliterallytoo short to converse with you further.

author: madires
author_rank: Super Contributor
timestamp: July 22, 2020, 02:35:30 pm
content: For shortwave some random long wire (might also work for long and medium wave) plus 9:1 unun for 50/75 ohms coaxial input. For FM an inexpensive commercial aerial and a 300 ohms to 50/75 ohms balun for old radios.