On Sat,9/13/2014 5:01 PM, Don Wilhelm wrote:
One other comment regarding fan dipoles.
They really work well, but if one attempts to put more than 3 bands on
a fan dipole, the interaction can become frustrating to tune them all,
been there, done that, and have all the scars.
Strongly agree. Also, fans work best on harmonically related bands.
80/40 works very well, so does 20/15/10. 40/30/20 not so good.
I use separations of about 9 inches for 20/15/10, and about 15 inches
for 80/40.
A very high 20/15/10 fan will have Zo near 50 ohms, but an equally high
80/40 will be closer to 75-80 ohms, depending on what your ground is. I
feed my high 80/40s with RG11. Mine are up 110 ft.
On any fan, the longest dipole will have it's "normal" SWR bandwidth,
while the SWR bandwidths of the shorter dipole(s) will be about half
normal. That works great for 80, which is the widest band as a
percentage of frequency, and 40M is relatively narrow. No problem on
20/15/10 either, because we tend to use the bottom half of 10M.
73, Jim K9YC
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