Antenna Length For Small AM Transmitter

[greeneyehawk]

Does the antenna length for a small AM transmitter have to be hundreds of feet long? I know that this long length is optimal, but could it be a few inches and still work for short ranges in my house?

 

[MikeMl]

Yes, a random wire a few feet long will work up to a distance of 50 feet. The big problem will be at night, when the field strength from stations hundreds to thousands of miles distant will be stronger than your peanut whistle.

 

[BrownOut]

Just a piece of wire probably wont' do. I built a AM transmitter, and I had to add inductancte to my wire antenna to make it work. Problem with electrically short antenna is, it doesn't radiate very effectively. I think I ended up with about 1mH if inductance in series with my wire antenna to get a good distance (about 20 feet).

 

[4pyros]

Use multibles of the full wave lenght. IE 1/2 wave, 1/4 wave, 1/8 wave and you can load it to make a shorter ant.

 

[gary350]

Antenna is usually 1/2 or 1/4 wave length you will have to use the formula to calculate that I don't know your frequency. There is a cool trick to makes a compact antenna. Lets assume the formula says your antenna needs to be 100 ft long. Use some small enamel coated copper wire like maybe #24 enamel coated wire. Wind 95 ft of that wire into a coil around a toilet paper tube will work fine the last 5 ft can be a straight length antenna that sticks up into the air. You may want to experement for some odd reason 1/2 wave lengh may work better than 1/4 or the other way around so build both try them both see which one works best. That 5 ft antenna is optional you can make it 1 or 2 or 3 ft or any length you like be sure to wind more or less wire on the coil.