Topband: Tuning 160M Dipole

[N1BUG]

On 10/30/2012 07:56 PM, Bob K6UJ wrote:
> I believe with frequency changes of 10KHZ the wire length changes by about one foot.
> So if it is resonant at 1.800 and you trim off one foot it will be resonant at 1.810.
> If you can find the resonant freq (where the lowest SWR is) then you can see how far you have to move.


Usually I use an MFJ antenna analyzer to see what the frequency of 
lowest SWR is, then calculate how much to shorten (or lengthen) each 
end of the antenna: (234/current frequency) minus (234/desired 
frequency). That had worked well until I started putting up several 
antennas in close proximity to each other. With the current crop of 
antennas that method proved nearly useless, since the frequency of 
minimum SWR did not move by the expected amount. My somewhat 
uneducated assumption is that when the antenna is significantly 
interacting with something in its environment, all bets are off.

73,
Paul N1BUG