[Elecraft] Multi-band (Fan) Dipoles

[Edward R. Cole]

I am always amazed how some have so much difficulty making dipole antennas.

With multi-band dipoles (or Fans as it is being called here), tuning 
of one dipole interacts with the tuning of other ones.  It is not too 
bad with harmonically related bands as the non-resonant reactance 
isolates the others pretty well.  I made a 4125 KHz/5167 KHz dual 
dipole (Fan) for work and the two are so close in frequency that 
serious interaction took place.  The lower frequency dipole (4125 
KHz, Marine HF chan-4A) tuned pretty easily but 5167 (AK Emergency 
Chan) was extremely narrow in bw (10 KHz).  That made 5167 not usable 
in some kinds of wx.

But I have had a 80/40/20m dipole (now it is 80/40m) up for years and 
they are not that hard to tune.  You start with the lower freq 
dipoles slightly long and tune the highest freq. dipole first.  Then 
the next, and so on.  You should re-check tuning on the highest 
freq.after tuning the nest highest to see if it is affected and make 
adjustment.  I said not hard, but it does take longer to get all resonant.

Using one of the portable antenna analyzers it the ONLY way to go 
(much simpler and convenient).


73, Ed - KL7UW, WD2XSH/45
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