Hi,
If it is a self-supported tower, best option is to install a "lift". A top part
of a guyed tower, the one where the rotator is, and install four wheels. And a
couple of U shape rails along the tower.
This roller stuff has a steel wire down to the bottom with a small winch.
This system allows you to lift and lower the antenna with ease. For maintenance
or when bad weather.
In this picture you can see a 2 elements quad for 7 MHz, installed in a self
supported tower with lift system.
http://www.ea1ddo.es/galeria/albums/EA5CTE/normal_EA5CTE_28429.JPG
[http://www.ea1ddo.es/galeria/albums/EA5CTE/normal_EA5CTE_28429.JPG]
73, Maximo
________________________________
De: TowerTalk <towertalk-bounces@contesting.com> en nombre de Jim Thomson
<jim.thom@telus.net>
Enviado: sábado, 11 de marzo de 2017 17:06
Para: towertalk@contesting.com
Asunto: [TowerTalk] Cubex Mantis II
Date: Fri, 10 Mar 2017 14:52:30 +0000
From: Daniel Hileman <n9wx@hotmail.com>
To: TOWER TALK <towertalk@contesting.com>
Subject: [TowerTalk] Cubex Mantis II
Hi Everyone,
I am thinking about putting a Cubex Mantis II Quad (2 elements on 40m, 4
elements 20-10m) on my AN Wireless tower at about 72'. I am looking to see if
anyone has experience with this quad, or other 40m quads, and can tell me how
they like it. Looking for real life performance on 40m Vs a 2 or 3 element
yagi? I know there is quite the debate on this, but not looking for "opinions"
with no operational experience between the two. This would be quite an
undertaking to install and looking for whether those with 40m quads would do it
again, and if they thought the performance was better/worse/same as a 2 -3
element yagi.
Thanks and 73,
Dan N9WX
## at one time I seriously considered the cubex mantis 2 ele quad, with its 2
els on 40m. The plan was to install it on my 72 ft trylon freestanding tower.
After looking at the problem from several angles, I disregarded the quad.
Its a 3 dimensional night mare to install...and maintain. With its boom just
mere inchs above the top of the tower, the spreaders, if in an X.... would be
16 ft above the top of the tower.....and also 16 ft below the top of the
tower,so
88 ft to the top.....and 56 ft at the bottom. To install the wire loops, the
boom 1st has to be installed at aprx 27-28 ft above the ground..on the side of
the tower. The boom is rotated like a big pinwheel, while you install the
various wire loops. Once done, and coax + balun installed, quad is raised to
top of tower. My issue with the 40m quad is.... you have 4 x 26 ft fiberglass
poles = 104 ft in total..... none of which radiates, its just there to support
the loops. Thats more than m2 uses on its 80m yagi els. Thats a helluva lot
of windload imo.... vs a shorty 40, with 44 ft els. My f12 44 ft eles only
weigh 12.5 lbs....and have very little windload...and none if pointed into the
wind.
## With any vert polarized yagi, or mast out the top of a tower, or quad els,
whether mounted in an X or a diamond, you always end up with els that are
always broadside to the wind, regardless of direction its pointed. Several
friends had quads back in the day.....and all were a pita to maintain. One
year we had an ice storm, the quads ended up with broken wires on the REF.
All had to come down. The builders even tried teflon coated stranded wire,
thinking ice and snow would not stick. Nice try, doesnt work, it made it
worse. Back to regular wire. They even tried raw AC, with a variac, on the DE
to melt the ice, which works, sorta, but not on the REF. You cant stack
anything above or below a quad. VE7DXQ added 17 + 12m to his 20-15-10m
cubex quad. 17+15 m interacted badly....as did 12 + 10m. Was replaced with a
f12 5BA 20-17-15-12-10m yagi..and a F12 40m rotary dipole above it.
## Installing a quad on a guyed tower is a gong show, but has been done. Boom
next to tower at base..then raised. Once you get to 1st set of guy wires, they
are removed at the tower, boom raised a bit, then 3 x guys re-installed. 3 x
temp guys used for safety. Moot point with a free standing tower.
## IF u dont have ice, heavy wet snow, or high winds, or any combo of ice +
wind, you will probably be ok. The 2 el 40m quads I have heard were
flame throwers on 40m. But none lasted more than 2-3 years till problems
started. With a self support tower, even with a broken wire, you could still
lower it down the side of the tower, rotate the boom, till you got to the
problem area, then repair it. You might want to get names of actual mantis
owners, and get their opinions 1st. A lot of water under the bridge, and
cubex may well have beefed them up considerably.
Jim VE7RF
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