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Registered Member #163
Joined: Mon Feb 13 2006, 01:55PM
Location: caledonia ohio
Posts: 22
I love to listen to the radio am espicaly but all my favroite stations are too far away to here well. I am wondering ir there is a simple and inexpensive way to amplify an am signal (530-800 spicificaly) to feed into either a hacked alarm clock or into an old radioshack shortwave thats collecting dust in the corner of my room. most of the google hits have been usless or out of my price range. A nudge in the right direction of any info or resources i can use would be appricated. jay
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
I've had good results picking up a marginal AM station with a simple tuned loop set up next to radio receiver. Google "DIY tuned loop antenna". Mine was wound on a flat box like the one pictured at , but used just 1 winding and the tuning capacitor. Orientation of the loop matters a lot (same as with the ferrite stick antenna built into most AM radios). Design formulas and lots more links at
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
A nice easy question!
I don't know how much you know, so I'll keep it simple, and you can skip the bits you already know.
Consider your weak distant signal fading in and out of a lot of local man-made noise from computers and power lines, interfering foreign stations, and the crackles and crashes of lightning from thunderstorms near and far, and you'll see that if you were to simply amplify your signal you would also be amplfying all this noise, and you would gain nothing by it.
You need a way to pick out your signal from all the noise, whilst reducing all the unwanted signals and noise as much as possible.
At medium frequency (MF) (your AM band) a truly enormous improvement can be made by using a very simple directional aerial called a loop or frame antenna which boosts the stations it is at pointed at whilst reducing almost to nothing interfering noise and unwanted stations off to the side. They are especially effective at reducing local man-made radio noise, which has very much spoilt MF for many listeners.
A small variable capacitor to tune the loop, and a single cheap transistor, and you won't believe how much your signals can be improved.
If you think you can manage this (see the pictures of rotatable frame aerials below) I'll go into more detail presently...
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
Great question. Harry has the right idea, but let me build a little on that.
For receiving distant stations on AM, it's tough to beat a good loop antenna. Besides being cheap and relatively simple to construct, they have three primary advantages over an active antenna with an amplifier. First, loops need no ground, so you don't have to worry about connecting to water pipes or sinking a ground rod. Second, loop antennas respond to the magnetic portion of an electromagnetic wave, local noise sources with strong electric fields, such as power line noise, are greatly diminished. Third, loops are mostly omnidirectional, but there is a deep null on either side of the loop. This can be extremely useful at night, when stations tend to run together. Provided that the interfering station is in a different direction than the desired station, you can rotate the loop to null the interfering station out.
The links provided cover construction details, so I won't bother with all that. The Radio Shack receiver is probably your best choice for a receiver, as it will likely have an external antenna jack that will allow you to connect the loop without any hassle. If not, no worries -- I've seen others make the connection by either winding a few turns around the radio, or opening up the radio and winding a few turns around the ferrite bar inside.
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rf amplication
