small amp ?

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jrob709
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small amp ?

Post by jrob709 » Sat Mar 01, 2003 5:39 pm

i have a radio in my pole barn the type that you use a piece of wire for an antennae.<p>i have trouble picking up anything, question is can i put in a small class a amp. where the antennae plugs into the radio, i don't want to damage the radio

russlk
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Re: small amp ?

Post by russlk » Sat Mar 01, 2003 7:34 pm

What kind of radio is it? Is it AM or FM? Does it pick up anything? If not, the radio may be defective. If you are trying to receive FM signals, the antenna connections should have 3 screws. Two of them have a shorting jumper, the third will have the antenna wire attached. You can get better reception by using a dipole antenna or TV antenna which has two wires. In that case, remove the jumper and connect the two antenna wires to the two outside screws. If you want still better reception, you can use a TV antenna amplifier (available from Radio Shack).

jrob709
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Re: small amp ?

Post by jrob709 » Sat Mar 01, 2003 8:01 pm

its just a standard am/fm home radio and it worked great in the house i'm just having trouble picking up signals out in the pole barn possibly because of the metal skin of the building. i put a small cell phone like antenna on the roof and i can hear the music but its tough because of all the static. i think it may be a problem with a weak signal and i was going to use a small homemade amp with a gain of 20 or 50.<p>my intent of the first post was just to make sure that i didn't accidently damage the radio by using such a device. the antenna is meant to be just a piece of speaker wire or something similar. where it plugs into the radio it has 2 spring clip things that hold it there. i wanted to put in a small amp between the radio and the antenna.<p>will i just be amplifying the static or possibly get a few stations to come in ?<p>should i use a ic chip such as the 386 or a transistor design ?<p>thanks for all the info :)

russlk
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Re: small amp ?

Post by russlk » Sat Mar 01, 2003 8:38 pm

You have to amplify 100mHz, so the 386 won't work. The construction of a VHF amp is tricky, so I recommend that you buy one. To be effective, the amp has to be on the roof with the antenna. But, if you have a good TV antenna, you probably won't need an amplifier. Radio Shack $30 antenna with 300 ohm lead-in should be all you need. If you want to go minimum cost, you can make a dipole out of 300 ohm lead-in: Cut a section 4.9 feet long and short both ends. In the center, cut one wire and attach the two lead-in wires. Fasten the dipole to a wood or plastic support such that the dipole is horizontal and at least 5 feet above any metal. The antenna will receive best broadside.

Dimbulb
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Re: small amp ?

Post by Dimbulb » Sat Mar 01, 2003 9:48 pm

If the roof is metal it may be acting as a shield.
You could try to get higher than the roof with a plastic pipe and a 48 inch whip. A coax is run down to the radio. Since the radio works ok in the house an amplifier would be a waste.

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haklesup
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Re: small amp ?

Post by haklesup » Sat Mar 01, 2003 11:44 pm

If the biulding is entirely covered in metal than that is your problem. You are in a fariday cage. You can have the best antenna on a sensitive radio but it is still shielded from the signal. You need to get the antenna outside. <p>Try a simple FM Dipole (T shaped wire) and hook it up to the spring clips. Run the wire through the wall and put the T part outside a foot or more away from the building's metal skin. In any case, probably any outdoor antenna will work and an amplifier is probably unnecessary. Getting the antenna up high or getting the ground plane perpendicular and below the antenna rather than beside it will help reception but I think the basic solution is to get it outside the building.

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