Normally I don't say much on these reflectors because there are too many
"experts" standing by waiting to tell me the theory of why my antennas don't
work. Here are my experiences with 80 Meter quarter wave slopers. I have a
70 foot Rohn 25 tower with an 8 foot mast. A CushCraft D3W is attached to
the mast at the 77' point. A TH7DX is attached to the mast at the 72" point.
My four 80 Meter slopers are attached to the tower at the 60' point. Each
sloper is 67' of insulated copper wire oriented NE - SW -NW- SE. I switch
between wires using a DX engineering antenna switch box. Each sloper is
attached to assorted supports on the bottom end, but most are in the 10-15'
height range. At the base of the tower I have a #2 wire radial ring, which
I've attached about 50 quarter wave radials, and just laid them on the
ground. In about 2 years the grass grows over them and they disappear. In my
case there is nothing magic, just hook the sloping wire to the 60' point on
the tower. The center conductor of the coax is attached to the sloping wire
and the braid is attached to the tower. One trick I've found effective is to
have the upper insulator no more than 3/4" from the attachment point. The
closer the better. This antenna functions like a off center fed vertical, in
that the tower is the main radiator. NOW..the problem you are having with
160 meters is somewhat more complex, in that you don't have the height to
effect a 50 ohm match as easily as 80 Meters. The trick here is to find the
match point on the tower. I would suggest attaching the 160 Meter sloper to
the 35' height as a starting point. Stretch the 135' +- length of wire out
and attach the other end to a 20' +- support. This is a VERY tricky
operation in that there is NO "SET" "magic" attachment point on 160. You're
just going to have to keep trying different attachment heights, and end
heights. If you do find the "sweet spot" it will work like a charm! On 80
meters I have worked about 320 countries and it is HEAD and shoulders above
my other 80 meter antennas. If you don't already have one, purchase a Alpha
Delta sloper or at least look at one to get the idea how to arrange the
attachment point. he uses a simple aluminum plate with an so-239 connector
and a hole in the plate which is placed under one of the tower leg bolts.
Its super simple but 320 countries on 80 tells the story. If you need
further help please write.
73 & GL Mick W4YV
----- Original Message -----
From: "Stephanie WX3K" <firstname.lastname@example.org>
Cc: "Towertalk" <email@example.com>
Sent: Tuesday, January 01, 2002 1:17 PM
Subject: RE: [TowerTalk] Half slopers using a tower
> -----Original Message-----
> From: Tom Rauch [mailto:firstname.lastname@example.org]
> Sent: Tuesday, January 01, 2002 7:50 AM
> To: Towertalk; Stephanie WX3K
> Subject: RE: [TowerTalk] Half slopers using a tower
> Please explain what "5 or more above" implies.....There have been many
> others that have shared some very good results with the HALF SLOPER
> Sounds to me like this antenna is anything but a "free lunch" antenna.
> Taking the time to understand the functionality of an antenna is well
> its weight in gold to me, even if it means a little extra experimentation
> Besides isnt that the whole fun of the technical side of amateur radio
> Stephanie R. Koles WX3K
> >If you want a vertical, install a normal vertical like an Inverted L fed
> >at earth level and a good radial system, or shunt feed the tower and
> >use a good conventional radial system with it. it might be a little
> >work, but you will be 5 or more above any of the "free lunch"
> >systems that rarely if ever work as expected.
> >73, Tom W8JI
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This list is sponsored by the new eHam.net Store. When you buy products
like ICE filters, Array Solutions StackMatch, or M-Squared Antennas from
the eHam Store for the same price you pay direct, a portion of the sale
price goes to support this list. Check it out at http://www.eham.net.
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Administrative requests: towertalk-REQUEST@contesting.com