[Mobile-Portable] Re: 10 meters - coax length

[Scott Townley]

Absolutely NOT true!  Smith chart shows it clearly...a mismatched load on a 
50ohm line defines a CIRCLE about the (matched) origin...you cannot get 
there from here with a pure transmission line.



At 17:14 2003-10-03, Gary Pearce KN4AQ wrote:
>At 07:42 PM 10/3/2003, K2YGM wrote:
>
>>There are times where the coax needs to be either trimmed or lengthened.
>
>Those "times" are when the antenna is not presenting a 50 ohm impedance of 
>the frequency you're transmitting on.  If the antenna IS a 50 ohm load on 
>your transmit frequency, it doesn't matter what the coax length is - it 
>will be 50 ohms everywhere along its length.  But if the antenna is not 50 
>ohms, the impedance you see at the end of the coax will go up and down 
>with the length of the coax, crossing the 50 ohm point every 1/4 
>wavelength.  Get the length of the coax right under those conditions, and 
>the transmitter is happy.  The antenna won't radiate quite as well, but it 
>will radiate.  It's a useful trick when you can't get the antenna adjusted 
>correctly.
>
>73,
>Gary KN4AQ
>
>
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Scott Townley NX7U
Gilbert, AZ  DM43di
http://members.cox.net/nx7u