Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
Liam,
You are absolutely right that the antenna cannot radiate more power than you feed it. They are probably talking about "effective ratiated power", which is closely related to antenna gain. You get more power at the receivers, but only in the directions where radiation is maximized. For example, a Yagi directs the power more in one direction, and a "vertical collinear" directs it in a horizontal plane. Each does so at the "expense" of power radiated in other directions, but if you don't care about reaching receivers in those other directions, it's not a problem. But be careful: do the rules limit the maximum power, or the maximum ERP (effective radiated power)? (The same thing works for receiving, too. You can use antenna directivity to increase the received signal level, and to reject signals or noise coming from directions you don't care about receiving.) Cheers, Tom Liam Ness wrote in message . .. I've been homebrewing some simple part 15 transmitters and have always thought that I was safely within part 15 by controling the RF output. I use a spice program to estimate my output levels. I just read a web page that suggests a antenna can increase the RF output power and I wanted advice if that is true. It was suggested that output could be increased from 30milliwatts to 60milliwatts by using this antenna. I understand how you could increase voltage with a decrease in amperage and vice versa, but I was under the assumption that you couldn't increase total power without adding more power. I thought it would violate one of the laws of thermodymanics otherwise. They didn't seem to be talking about more effieciently radiating the transmitters power, but actually increasing it above what is present at the antenna port. Could someone confirm whether it is posible to increase the power output of an RF transmitter above the total presented to the antenna. If it is, I'd appreciate any pointers to information about this. I don't want put myself out of part 15 by a poor antenna choice. (even though I still can't believe that it is possible, it sounds to much like perpetual motion) TIA |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Inverted ground plane antenna: compared with normal GP and low dipole. | Antenna | |||
Current in loading coil, EZNEC - helix | Antenna | |||
Antenna tuner | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
QST Article: An Easy to Build, Dual-Band Collinear Antenna | Antenna |