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deepak007
Joined: 20 Sep 2007
Posts: 71
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 19 Aug 2008 5:01 antenna connection |
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hello
i have a small doubt. i have a rf preamp circuit which an antenna input and an output connection. each connection has two wires antenna and ground.it is designed for dipole. if i use a whip antenna. how do i connect?
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vfone
Joined: 10 Oct 2001
Posts: 1759
Helped: 229
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| 19 Aug 2008 7:26 Re: antenna connection |
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| If was designed for a dipole just connect one wire to the ground and the other wire to your whip antenna.
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deepak007
Joined: 20 Sep 2007
Posts: 71
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| 19 Aug 2008 20:30 Re: antenna connection |
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| if i want to use a whip instead of dipole, can i omit the ground connection?
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Eugen_E
Joined: 29 Nov 2004
Posts: 326
Helped: 30
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| 19 Aug 2008 22:29 Re: antenna connection |
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You should be careful so the output of the amplifier is terminated on correct impedance, and use coax cable and connectors.
If you have loose wires in RF, and the whip antenna is near, also connected with common wires, the amplifier may oscillate, because the antenna will couple back the amplified signal, resulting in feedback and oscillations. This is true especially if the amplifier has a high gain and uses UHF/SHF transistors.
A groundplane antenna is more correct.
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 20 Aug 2008 2:21 Re: antenna connection |
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If your antenna has an even remotely 50 or 70 ohm impedance, you will benefit from using the amplifier if it near the antenna. This will prevent the transmission line loss to your receiver form causing harm.
However, if you are listening to high power broadcast transmitters, the use of this amplifier is a moot point.
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RF-OM
Joined: 03 Aug 2007
Posts: 607
Helped: 113
Location: The Earth
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| 21 Aug 2008 23:24 Re: antenna connection |
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| If you are in TV or FM broadcast band the best way is to use TV balun (e.g. from Radioshack).
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