Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
11/23/09 15:02
Read: times


 
#171066 - Allthough looking very simple...
Responding to: ???'s previous message
...an antenna is a highly complicated thing. It has to do with resonances and impedance matching to the electromagnetic wave and to the input of reciever. It has also to do with how good the antenna's footpoint sees earth, etc. etc. I have seen antennas, which are tuned to 5/8 x Lambda and using a coil to compensate for "something". I have never understood this in full detail to be honest...

I have learned, that the highest level of efficiency (100%) can be achieved, when the antenna's length is lambda/2 (best conditions assumed). For shorter antennas the effiency decreases by the following law:

efficiency = 8 x length^3 / lambda^3

So, with an antenna that is not 1.5m at 100MHz but only 15cm, the efficiency drops to 0.1%!

Kai Klaas

List of 10 messages in thread
TopicAuthorDate
FM Radio - Antenna            01/01/70 00:00      
   Self-tuning            01/01/70 00:00      
   Note: "Off-Topic" Scores            01/01/70 00:00      
   A couple of thoughts            01/01/70 00:00      
      Ahh, Smith chart            01/01/70 00:00      
      Allthough looking very simple...            01/01/70 00:00      
         The mystical "something."            01/01/70 00:00      
            Short antennas            01/01/70 00:00      
               Questions            01/01/70 00:00      
                  Comments            01/01/70 00:00      

Back to Subject List