# How Much Power for the Antenna?

Discussion in 'General Electronics Chat' started by sjgallagher2, Dec 3, 2013.

1. ### sjgallagher2 Thread Starter Member

Feb 6, 2013
106
7
How do I determine how much power to input to a dipole antenna, when I know the range? I've heard 1/4 watt can transmit for a mile, but how do you get that without practical experimenting?

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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Learn to use a Path Loss Calculator like this one.

You have to consider frequency, TX and RX antenna gains, coax losses, TX power, RX sensitivity, and distance for starters

3. ### Papabravo Expert

Feb 24, 2006
10,021
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And there are other variables including time of day, season of the year, and position in the 11-year sunspot cycle. Right now we are supposed to be at the Solar Max, but sadly ole Sol is not cooperating.

4. ### sjgallagher2 Thread Starter Member

Feb 6, 2013
106
7
Thanks Mike, you seem to know a lot about radio and you've been a huge help to me lately! Another question though, as far as transmission lines go. If I have a transmitter circuit, running at 900MHz, that leads straight to the antenna, should I take the output of the circuit and connect it to an RG8X coax cable? What kind of connector do I need at 900 MHz? Should I use a different type of cable?

5. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
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Usually there is at least a short length of coax between a transmitter or receiver and its associated antenna. At 900MHz, I would be looking at BNC,TNC or SMA connectors.

Don't forget that an antenna needs to approximate a center-fed 1/2 wavelength dipole; a 1/4 wavelength monopole without a ground plane (or the other 1/4 wavelength of the dipole) is a crappy antenna.

6. ### sjgallagher2 Thread Starter Member

Feb 6, 2013
106
7
Thanks a million Mike! You're a huge help