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Mudderoy
09-17-2012, 10:32 PM
One of the big differences between CB and HAM radio is that in HAM radio you have to deal with the equivalent of thousands of CB channels.

The spectrum consists of many different bands. Each frequency has an associated antenna length. You can have several antennas of varying lengths that are sized to operator on these bands, then you can manually switch them as you change bands on your radio.

Then came automatic antenna tuners!

With the press of a button the automatic antenna tuner takes one antenna and matches it to the radio so you can use it in just a few seconds.

http://youtu.be/8VOYmxT77Rk

You can read more about this on one of :xjtalk: sister sites di-dah-dit.com

:link: (http://www.di-dah-dit.com/showthread.php?504-Automatic-Antenna-Tuner)

bluedragon436
09-24-2012, 04:57 PM
I thought these things were an awesome design when I started researching the need to have diffent length antennas depending on what frequency you were going to be using... Thought it seemed a bit stupid to have multiple ant.'s of different lengths just to enjoy your rig... but using something like this makes it simple to use just one ant. for the majority of the freq's you plan to use..

Mudderoy
09-30-2012, 10:37 AM
I thought these things were an awesome design when I started researching the need to have diffent length antennas depending on what frequency you were going to be using... Thought it seemed a bit stupid to have multiple ant.'s of different lengths just to enjoy your rig... but using something like this makes it simple to use just one ant. for the majority of the freq's you plan to use..

Well it's a compromise. Having a matched antenna for the frequency that you are operating on is going to give you the best performance.

So 3 to 7 antennas, an equal number of transmission feed lines and a big old multi-position switch box to select the antenna is usually the way to go.

You could still use the tuner even in this config. The lower in frequency (bands) you go the more narrow the range of your resonance in your antenna. So you have to build your antenna to match the freq range you want to operate in. This could be just 40 KHz wide (or less). A tuner would allow you to move outside the 40KHz envelope. There are other ways to increase the bandwidth of your antenna but there go those compromises again. :D