Receive antenna only

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nezza

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Dec 6, 2014
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Hi everyone,

Quick question, when it comes to scanning, does it make a difference if the antenna is 0 gain or 12dBi gain? I am using a 12dBi gain antenna for scanning at the moment but was thinking about a discone which is 0 gain. The 12dBi does a good job picking up distant stations.

When it comes to receiving only, does gain make a difference?

Thank you.
 

jwt873

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Generally, the higher the gain, the less bandwidth you have.

Discones cover a wide range of frequencies (typically 25 Mhz to 1300 Mhz). The gain is roughly the same on all frequencies it it was designed for. It will receive just as well at 25 Mhz as it will at 1300 Mhz.

High gain antennas have narrower bandwidths. They 'specialize' in a narrow range of frequencies. So, if you have an 800 Mhz antenna with 12 dbi gain, it will perform very well at 800 Mhz, but horribly at 25 Mhz.

Yes, gain makes a difference for receiving. High gain antennas capture more of the incoming signal which results in a larger voltage at the receiver input. That's why they use dishes that are 40 yards wide to pick up signals from the satellites orbiting Mars instead of using simple discones :)
 

Ubbe

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Also remember that you can make an antenna more directional to add more gain. An omni antenna can be designed to not pick up much RF from the sky and instead flatten the loob and concentrate on the horizon where the transmitters are.

A yagi antenna will additionally also narrow the loob horizontilly and make it directionally to increase gain.

It could also be a factor with the shear size of the antenna. A bigger antenna will pick up more RF energi and make it receive out of band frequencies better. A 12dBi gain 800MHz omni antenna might have the same 0dBi at 25MHz as a discone.

/Ubbe
 
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