[Antennas] [Fwd: Fan Dipole, R/S rotator]

Mon Sep 12 22:26:27 EDT 2005

From: "k3hx at juno.com" <k3hx at juno.com>
Date: Mon Sep 12 21:10:29 CDT 2005
To: k1kq at motorhomeusa.com, k3hx at verizon.net
Subject: Fan Dipole, R/S rotator
OM,
A fan dipole is an arrangement where the longest dipole element
acts as a support for other dipole elements strung below it.
Most often, these supported dipole elements are set to operate on
a harmonic of the support dipole's frequency. For example 40-20-15.
I have had good luck with this technique spacing the harmonic elements
4-6" below the support dipole. Use lightweight spacers, I used 120
size film rolls with good results when spaced about 18" apart.
You can use "strong" wire for the long top support dipole and 
smaller, lighter gauge wire for the harmonic elements. It takes some
time to trim the antenna for best VSWR as there is some interaction
between the elements. Start with the highest frequency and work to
the lowest. 
You can put up a "fan" with non-harmonic dipole lengths but it is
a real pain to tune and even when you are finished, it may require a
tuner on TX for the higher frequency. For example, I had a 40-30 fan 
up at 43'. Took days to get the 30m element to be "less awful" as it 
would couple to the 40 meter element. That said, when I was finished,
the 40-30 fan heard better than the 40m dipole alone on 30 meters. Had
to use a tuner with the thing when transmitting on 30 meters.
0-------------------**--------------------0 40 meter support dipole
 ----------**---------- 20 meter dipole
 -----**----- 15 meter dipole
The Radio Schlock TV rotor appears to be a clone of the Channel Master 
9510 rotator. My experience with the latter is that they are reliable
and give good service over many years. They are, however, not 
terribly strong and I'd not put more than a 3 element 6 meter beam and
a 10 element 2 meter beam on them. If you go more than about 5' 
above the rotator to mount things, there is an alignment bearing
that serves to transfer the bending moment from the rotor to the mast. 
You will have to get it from a Channel Master dealer.
73,
Tim
___________________________________________________________________
Try Juno Platinum for Free! Then, only 9ドル.95/month!
Unlimited Internet Access with 250MB of Email Storage.
Visit http://www.juno.com/value to sign up today!