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temporary AM antenna

S

stephend2

THE PROPOSED ANTENNA WILL CONSIST OF A VERTICAL WIRE 18.28 METERS LONG SUSPENDED FROM THE CENTER OF A HORIZONTAL 'FLATTOP' APPROXIMATELY 79 METERS LONG AND APPROXIMATELY 18 METERS ABOVE GROUND (LESS SAG).

THE GROUND SYSTEM WILL CONSIST OF 50 COPPER GROUND WIRES BURIED SEVEN TO FOURTEEN CENTIMETERS (THREE TO SIX INCHES).

this is what is filed with the fcc on the STA application. I know very little about antennas, definitely want to learn. I can physically put it together, I'm lost on what it's going to take to match this load to the transmitter.
 
Stephen, before R. Fry** jumps in with his usual hard-core technical wizardry and counsel -- let me say that I hope you'll find this to be a fun project. Ham radio operators load their transmitters into unusual loads all of the time, but I find that there's something magic about doing it on the broadcast band where everyone can hear the results of your work.

**Beat him to the punch and look up AM Matching Network
 
Interesting specification for a temporary antenna...any idea who designed it?
 
A NEC model using 6mm OD conductors for this Tee antenna with the wire lengths, geometry and frequency shows a feedpoint impedance of about 13 +j 167 ohms. Non-radiating supports were assumed for the horizontal wire of the Tee.

The feedpoint impedance of the actual installation will depend on the length of the 50 buried radials, and the conductivity of the soil within about 1/2-wavelength from the base of the vertical wire.

Probably the best approach is to get a quotation from suppliers such as Kintronics to design, build and install the matching network that will be needed.
 
I have no idea who designed it, I'm assuming whoever filed the STA. All I was given to go on was that filing, the owner of the station wouldn't know an antenna or transmitter if it was in front of him....
 
What's wrong with the licensed antenna?
 
It will not be a very effective radiator. With the horizontal support wire, it will be directional as well.
 
frankberry said:
It will not be a very effective radiator. With the horizontal support wire, it will be directional as well.
Click to expand...

Sorry, but that belief is incorrect. The r-f currents on each half of that horizontal wire will be equal, and flowing in opposite directions at every instant of time. Therefore the useful far-fields it radiates will cancel. Also, they are horizontally polarized, and even their nearby groundwave fields are nearly useless.

The horizontal wire adds capacitance to the vertical wire, which increases its radiation resistance, and improves the radiation efficiency of that antenna system (other things equal).

All of the useful radiation from a Tee antenna originates from the vertical wire, and the ground reflection of that radiation.
 
Isn't this supposed to be the next product from the Hillbilly Engineering Corporation, aka the Southern Company (Big Grins). Enjoy this project. It's fun getting odd loads to play well on broadcast channels.
 
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