AM radio

Thread Starter

Mellisa_K

Joined Apr 2, 2017
390
Hello,

In Australia where I live the public radio and TV broadcaster (ABC) still broadcasts radio in AM.

One of the stations I am addicted to is called ABC News 24. It comes in particularly weakly. Most AM radios cannot receive its signal well enough to listen to comfortably.

I was wondering about building an AM receiver that has extra strong signal gain - enough to enjoy my addiction without inteference.

Any ideas?

Thankyou in advance,

Mell
 

Thread Starter

Mellisa_K

Joined Apr 2, 2017
390

Yaakov

Joined Jan 27, 2019
3,316
My radios have an inbuilt telescoping antenna but this makes no difference and there is no facility to plug in an external antenna.
The teleccoping antenna is for FM band reception and it not part of the AM circuit. The AM radio uses an internal loopstick antenna. This is a coil of very fine wire on a ferrite core.

The problem for portable AM receivers is the antenna. The wavelength of 1026 KHz is 292m so an effective quarter wave antenna would have to be 73m!

Unfortunately, there is no easy way to make an AM broadcast band receiver a lot better. There are much better commercial portables, but I don't know what you are currently using so I can't tell you if you ca do much better.

Building something yourself, that would be portable, and have exceptional performance would be very hard. You might want to consider buying a better receiver.
 

Thread Starter

Mellisa_K

Joined Apr 2, 2017
390
The teleccoping antenna is for FM band reception and it not part of the AM circuit. The AM radio uses an internal loopstick antenna. This is a coil of very fine wire on a ferrite core.

The problem for portable AM receivers is the antenna. The wavelength of 1026 KHz is 292m so an effective quarter wave antenna would have to be 73m!

Unfortunately, there is no easy way to make an AM broadcast band receiver a lot better. There are much better commercial portables, but I don't know what you are currently using so I can't tell you if you ca do much better.

Building something yourself, that would be portable, and have exceptional performance would be very hard. You might want to consider buying a better receiver.
Thanks Yaakov.
 
The telescopic antenna would only be for FM, the AM antenna will be an internal ferrite rod.

I don't know what part of Adelaide you are in, but I guess you are listening on 972kHz to 5PB which is a relatively low power transmission at 2kW from a mast at Wingfield. If you have tried other radios and they are all poor then you may be in a poor signal area or a high interference area. This service is also available via digital radio (DAB) which in Adelaide is transmitted from Mt Lofty. If you get good TV reception you may get good DAB reception so it may be worth trying a DAB radio. I don't live in Adelaide and I don't have DAB radio so this is just a suggestion, not a recommendation. Ask around if any neighbours are using digital radio and see what their reception is like.

Alternatively stream it from the internet via your home WiFi to your phone or tablet. You can add some bluetooth speakers, the sound is good and they are very convenient.

Improving the reception is difficult if you want to keep the device portable, but if you just want the pleasure of building your own radio then that's a whole other ballgame.
 

Thread Starter

Mellisa_K

Joined Apr 2, 2017
390
The telescopic antenna would only be for FM, the AM antenna will be an internal ferrite rod.

I don't know what part of Adelaide you are in, but I guess you are listening on 972kHz to 5PB which is a relatively low power transmission at 2kW from a mast at Wingfield. If you have tried other radios and they are all poor then you may be in a poor signal area or a high interference area. This service is also available via digital radio (DAB) which in Adelaide is transmitted from Mt Lofty. If you get good TV reception you may get good DAB reception so it may be worth trying a DAB radio. I don't live in Adelaide and I don't have DAB radio so this is just a suggestion, not a recommendation. Ask around if any neighbours are using digital radio and see what their reception is like.

Alternatively stream it from the internet via your home WiFi to your phone or tablet. You can add some bluetooth speakers, the sound is good and they are very convenient.

Improving the reception is difficult if you want to keep the device portable, but if you just want the pleasure of building your own radio then that's a whole other ballgame.
Thankyou for such a comprehensive reply Tesla23.

I would like to build a radio just for the pleasure of it. Sounds like and AM radio is out of the question. Perhaps a DAB radio. I could buy one but i would like to explore the option of making one. Can you point me please?
 

Yaakov

Joined Jan 27, 2019
3,316
Could you expand on this please: "The wavelength of 1026 KHz is 292m so an effective quarter wave antenna would have to be 73m!"
As you may know, every radio frequency have a corresponding wavelength which is a physical size. It is the distance the wave can propagate based on it’s speed, which is the speed of light, and how quickly it is changing direction, which is the frequency.

The formula λ = v / f (where λ is wavelength, v is velocity, and f is frequency) will get you the length in meters.

For 1026 KHz, the wavelength is 292m. The shortest, simple resonant antenna is a ¼ wave dipole antenna. 292/4 = 73 making the shortest simple antenna for the frequency 73m long. The loopstick antenna in the radio uses various “tricks“ to make a physically smaller antenna electrically equivalent to this (or some other resonant fraction), but the practical upshot is that a “good” antenna at this frequency is much larger than portable.

If you have seen the tower for an AM broadcaster you are not looking at something that supports the antenna like you’d see for FM or television, you are seeing the antenna itself. It is very large.
 

Yaakov

Joined Jan 27, 2019
3,316
Bt the way, loopstick antennas exhibit considerable directionality and you might find that rotating the radio horizontally can improve reception.

The antenna will have two lobes 180° apart, as you turn it you should be able to find two peaks in the signal strength which, for a weak station, should be noticeable. These will happen when the long side of the stick is facing the source, front or back.
 

bertus

Joined Apr 5, 2008
21,446
Hello,

What radio are you currently using?
You say it has no external antenna connections.
You could try a loop antenna as @Yaakov said and "connect" it to the radio with a small loop around the radio.

loop antenna to radio.png
Bertus
 

Dodgydave

Joined Jun 22, 2012
10,027
Hello,

In Australia where I live the public radio and TV broadcaster (ABC) still broadcasts radio in AM.

One of the stations I am addicted to is called ABC News 24. It comes in particularly weakly. Most AM radios cannot receive its signal well enough to listen to comfortably.

I was wondering about building an AM receiver that has extra strong signal gain - enough to enjoy my addiction without inteference.

Any ideas?

Thankyou in advance,

Mell
I wouldn't bother making your own, buy one that's got a good specification , like a SW receiver, and a better antenna like a long wire or loop .

https://ccrane.com/how-to-make-a-simple-powerful-am-loop-antenna-for-free/

What radio do you have at the moment?
 
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As you may know, every radio frequency have a corresponding wavelength which is a physical size. It is the distance the wave can propagate based on it’s speed, which is the speed of light, and how quickly it is changing direction, which is the frequency.

The formula λ = v / f (where λ is wavelength, v is velocity, and f is frequency) will get you the length in meters.

For 1026 KHz, the wavelength is 292m. The shortest, simple resonant antenna is a ¼ wave dipole antenna. 292/4 = 73 making the shortest simple antenna for the frequency 73m long. The loopstick antenna in the radio uses various “tricks“ to make a physically smaller antenna electrically equivalent to this (or some other resonant fraction), but the practical upshot is that a “good” antenna at this frequency is much larger than portable.

If you have seen the tower for an AM broadcaster you are not looking at something that supports the antenna like you’d see for FM or television, you are seeing the antenna itself. It is very large.
Australia, a big country. Lot of space. Who knows, maybe that antenna could be built.
 
In my youth, I rebuilt many AM radios to increase sensitivity. I added a voltage repeater on a single field-effect transistor (JFET) with a pn junction. I connected the magnetic antenna resonant circuit to the gate. From the source I fed the signal further. The sensitivity increased considerably. The connection scheme of the additional stage is determined by the circuit of the radio receiver. It was easy for me. At that time in the USSR they used to give wiring diagrams for manufactured radios. If you can get hold of the electronic schematic of your receiver, I will give you a refinement.
 
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