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

[Gary Pearce KN4AQ]

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