[AMRadio] 50 ohms simple question


Fred Nerks fnerks1 at yahoo.com
Thu Apr 5 17:24:20 EDT 2007


--- Alan Beck <abeck at xplornet.com> wrote:

> Basic question
> 
>  
> 
> Why is it that my radios are 50 ohms and the
> impedance at the feed point at
> the antenna (pure dipole) is 70 ohms.
>
> Am I mistooken
> 
> Alan
> 

Yes Alan, You are mistaken. As you will find from the
many different responses (with opinions) this question
will surely generate... this is not a "basic"
question. 

There is a very acceptable range of impedance (ohms)
that will work just fine for you. If you want to split
hairs (or ohms) then get an SWR meter or some form of
analyzer and either adjust the length of your antenna
to something near 50 ohms or use a tuner that can
match the feedline and the antenna to 50 ohms. There
are several possible ways to transfer power to an
antenna in a ratio of 50 volts per ampere of current
that many transmitters like to see. 

Transmitters manufacturers have chosen 50 ohms based
on the most commercially available and popular
transmission lines on the market with consideration to
the many different antenna systems in use other than
just a theoretical dipole.

Mike Mertes / KZ5M


 
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